Nutrient Requirements of Different Animal Species

Feeding Definitions

Acid Detergent Fibre (ADF) – a chemical analysis that estimates the total fibre (including indigestible lignin) in the feed. A high ADF indicates reduced digestibility and likely lower voluntary feed intake.
Amino Acids – nitrogen-containing molecules that are the building blocks used to create protein in the body.
Available Protein – the portion of crude protein that can be digested by the animal. It represents the proportion of total protein after deducting the ADF-N fraction of a feed.
Carbohydrate – a source of dietary energy that includes starches, sugars, pectins, cellulose and hemicellulose. All carbohydrates contain carbon, hydrogen, and oxygen, and are usually divided into two types: structural (fibre from plant wall) and non-structural (sugars and starches from plant cell contents).
Cellulose – a fibrous carbohydrate that is the main part of plant cell walls.
Chelated Mineral – a chemical bond formed between an organic molecule and a mineral that increases mineral bioavailability to the animal and can reduce the excretion of excess minerals in manure.
Crude Protein (CP) – an estimate of the total protein content of a feed determined by analysing the nitrogen content of the feed and multiplying the result by 6.25. Crude protein includes true protein and non-protein nitrogen sources such as ammonia, amino acids, and nitrates.
Digestible Energy (DE) – the apparent energy that is available to the animal by digestion, measured as the difference between the gross energy content of a feed and the energy contained in the animal’s faeces.
Fat-Soluble Vitamins – stored in the animal’s fat reserves or liver, including A, D, E, and K.
Hemicellulose – a carbohydrate found in plant cell walls that is more complex in structure than sugars but less complex than cellulose.
International Unit (IU) – a standard unit of the potency of a biological agent, such as a vitamin, hormone, vaccine, or antibiotic.
Neutral Detergent Fibre (NDF) – an insoluble fraction containing all plant cell wall components left after boiling a feed sample in a neutral detergent solution. A high NDF indicates lower digestibility and voluntary feed intake.
Non-Protein Nitrogen (NPN) – urea and ammonia are compounds that can be used by the microorganisms in the rumen to form true protein, which can then be converted to meat or milk by the animals. When feeding low-quality, low-protein feeds, urea can help the ruminal bacteria to create true protein.
Non-Structural Carbohydrate – comprised of sugar, starch, and pectin, this is the non-NDF fraction of feedstuffs.
Rumen Degradable Protein (RDP) – the portion of dietary protein that is degraded in the rumen. It feeds the rumen bacteria, supplying microbial protein.
Rumen Undegraded Protein (RUP) – the portion of dietary protein that escapes degradation by ruminal microorganisms and passes into the small intestine where it is digested and absorbed.
Structural Carbohydrate – the fibrous, cell wall or support structure of the plant, containing cellulose, hemicellulose, and lignin.
Water Soluble Vitamins – include the B complex vitamins and vitamin C. They are generally not supplemented to cattle after two months of age, due to the ability of rumen microbes to manufacture them in adequate amounts.
Non-Degradable Protein – non-degradable proteins are proteins that are not attacked by the micro-organisms of the rumen. Thus, they pass, unaffected into the abomasum and are digested by the acids there.

Filling the Gaps

The nutrient requirements of the herd and the nutrient provision of the natural pasture are now superimposed on each other. Where a shortfall of nutrients occurs, the pasture can be supplemented with either energy-rich licks or protein-rich licks as required. As a general rule, a salt lick containing minerals should be provided all year round.

Keep in mind that with ruminants the farmer is feeding the microorganisms in the rumen and not the ruminant animal itself. Therefore, all feed management decisions should keep the livelihood of the microorganisms in mind. For example, any changes in feed should be done slowly over at least 7 days.

Furthermore, inexpensive NPN sources such as urea (or sterilised chicken litter) can be used instead of expensive protein resources such as lucerne, fish meal, and so on. This is because the microorganisms are capable of using these NPN resources in the synthesis of amino acids and proteins.

The Characteristics and Different Classes of Nutrients

The majority of animals obtain their nutrients by consuming other organisms. Amino acids, lipid molecules, nucleotides, and simple sugars are the biological molecules required for animal function at the cellular level. However, the food eaten is high in protein, fat, and complex carbohydrates.

These macromolecules must be converted by animals into the simple molecules required for cellular functions such as the formation of new molecules, cells, and tissues. The conversion of food into nutrients is a multi-step process that includes digestion and absorption. Food particles are broken down into smaller components during digestion and then absorbed by the body.

As mentioned earlier, the nutrient requirements (quantity and quality) of different animals differ depending on their species, breed, age, sex, production potential, stage of production, whether they are ill or healthy and the product they produce (whether wool, meat, milk, and so on).

These factors will influence the nutrient requirements of animals throughout their lives. Animals obtain their nutrition from the consumption of other organisms. Depending on their diet, animals can be classified into the following categories: plant eaters (herbivores), meat eaters (carnivores), and those that eat both plants and animals (omnivores).

Desirable Characteristics of Nutrition:

The quantity of the feed should meet the requirements and production of the animal.
The nutrition provided should be palatable.
Balanced nutrition is the key to healthy growth. There should be a better and more balanced mixture of proteins, vitamins, and other nutrients.
The mineral matter should be present in enough quantities.
The feed should be fairly laxative to avoid constipation and other digestive troubles in the animals.
The feed should be fairly bulk.
Regularity in the feed timings should be maintained.
There should be enough green succulent fodder as they are bulky, nutritious, and easily digestible.
Sudden changes in the feed should be avoided.
It should be economical in terms of labour and cost.

In general, nutrient requirement tables indicate the nutrient requirements of different age animals for their maintenance requirements as well as for different levels of production. Production indices could include growth, milk production, gestation (pregnancy) or fibre production.

Definition of Maintenance and Production Rations:

Maintenance Ration: A maintenance ration is one, which provides sufficient nutrients for the maintenance of the essential processes of life. The animal will remain in good health without a decrease or increase in body mass. Maintenance requirements are mainly dictated by the body mass of the animal.
Production Ration: A production ration provides nutrients over and above the maintenance ration to ensure the production of a certain product. Products include growth (meat), milk, young and fibre.

Do not be fooled by an animal’s apparent lower nutritional requirements at particular stages of its life. To prepare for the demanding high-production phase that will follow, a pregnant dairy cow, for example, needs to store up reserves of fat, muscle, tissue, and bone during the dry period. Additionally, feed provision and nutrient supply should be constant to prevent breaks or weak spots in the fibre, even though the production of fibre does not always require a higher nutrient supply. To ensure a buffer for unforeseen stressful situations that could adversely affect the quality of the fibre because abrupt weather changes can hurt feed intake, producing animals should be fed slightly more than maintenance requirements.

Typically, the cost of feeding a livestock operation accounts for 70% of total costs. Feeding the herd has a cost, regardless of whether the farmer produces the feed on the farm or buys it from outside vendors. Feed formulation is the process by which the farmer determines which feeds are necessary to meet the nutritional needs of his animals while spending the least amount of money possible. The farmer will need to be aware of the following to accomplish this:

What feeds he currently has available?
The quantity and quality of the available feeds.
The nutrient requirements of his or her animals.
The stage of production and level of production of his or her animals (high milk. producers vs. low milk producers or dams carrying singles or dams carrying twins).
Shortages in nutrients may occur.
Which feed resources can be used to supplement the shortages?
The costs of feed production, mixing, supplementation, or outright purchase (including costs of transport and storage).
The seasonality of feed production and seasonality of feed purchase.

Since feed represents the largest input cost in a livestock operation, managing, controlling, and monitoring the management of feed is one of a livestock farmer’s primary management responsibilities to ensure effective utilisation with minimal wastage at the lowest possible cost and the highest possible production. In a livestock operation, managing feed is a daily management task rather than a one-time occurrence. Every farming enterprise should have a well-designed feed flow programme in place to effectively control the costs of this input.

Feeding Management of Swine

It is discovered that pig farming today is highly specialised. Selection is being done for high fertility, high growth, the right carcass quality, and the correct feeding of their different life stages, keeping in mind that feeding accounts for 70 – 80% of the overall cost of swine feeding.

Decreasing the total nutrients in the feed or restricting the feed intakes of pigs is not a solution when trying to maintain growth performance and income from the operation. Ensure feeders are in good working condition to prevent feed wastage. Feeders should be frequently recalibrated and cleaned to ensure the correct quantity of feed is consistently provided to the pigs and to prevent feed from spoiling. Research shows that pelleted feed, compared to a meal, not only reduces feed wastage but also promotes feed intake.

Factors that should be considered in swine feeding:

1. The digestibility of the diet.

The digestibility of the feed is essential when it comes to ensuring pigs fully utilise the nutrients that the feed has to offer. The type and quality of raw materials are key aspects to consider when producing animal feed products.

Ensuring the correct high-quality raw materials are used can improve the digestibility of the feed and improve animal performance. Protein is one of the most expensive nutrients in the diet and contributes heavily to the total cost of feed. When done correctly, reducing the total protein content of the diet whilst ensuring the correct level and ratio of amino acids, can improve the digestibility of the diet and maintain animal performance at a lower feed cost.

2. Consider raw material availability and cost.

Certain substitutions of expensive raw materials for more affordable options can successfully be achieved where expert knowledge and qualitative protocols are used. Although maize is the most widely used energy source for pigs in South Africa, grains such as barley and wheat can be considered good alternatives to reduce maize inclusion when they are available and more affordable.

3. Continuous review of the raw material nutrients.

A consistent and accurate evaluation of the raw materials in the feed will allow for more accurate feed formulations and superior animal performance.

4. Including enzymes in the feed.

Enzymes are protein compounds that increase the nutrient absorption of the feed by breaking down certain components that animals may have problems otherwise digesting. Enzymes allow for improved diet digestibility and when used correctly can be a cost-effective solution. Examples of enzymes commonly used include carbohydrates, proteases, and phytases.

5. A more accurate feeding approach.

Phase feeding is the changing of an animal’s diet according to its age, weight, or physiological state. It is designed to assist a farmer in achieving the most out of their feed, in the most cost-effective way.

Introducing an additional phase when feeding pigs – a phase that is more accurate to the age or production level of the pig – can result in cost-saving through improved feed efficiency. The practicality of feeding a higher number of phases should be considered when comparing this to the benefits of a more accurate feeding schedule.

6. Consider the in-feed medication costs.

Medication costs can be extremely expensive, which is why it is important to regularly consult with your veterinarian to ensure that the farm is on the correct medication program. Discuss with your veterinarian which medications are necessary depending on the health status of the farm and whether in-feed medications, in-water, or injectables will be the best solution.

7. Split sex feeding.

At the same age, growing pigs will have different growth rates and nutrient requirements according to their sex. Separating the grower herd into boars and gilts to feed specialised diets according to their sex will allow for a more efficient feeding and management program.

A. Nutrition and Feeding for Optimum Reproductive Performance of a Piggery

The Boar:

The main goal when feeding boars is to optimise semen quality and quantity as well as maintain the boar in the herd. However, minimal research has been done to determine the appropriate nutrition to develop and maintain boars. Therefore, the majority of seed stock producers and commercial boar studs fed developing boars about 10% greater nutrients than growing market gilts to maximise growth performance and bone structure.

Fig 5.35 Purebred Duroc boar.

Researchers have looked at enhancing semen quality. One area is in vitamin and trace mineral nutrition as research has shown that feeding higher dietary concentrations of selenium (0.5 ppm) and vitamin E (220 IU/kg) from weaning can improve boar semen quality, but the greater effect seemed to be from selenium. Selenium appears to have effects on sperm motility and abnormalities.

A grain-soybean meal diet fortified similarly to a gestation diet is generally satisfactory for meeting the nutrient needs of the mature boar. The daily feeding rate should be changed to reflect differences in season, condition, and workload of the boar. Boars under heavy workload should be fed 3 kg/hd/d. Care should be taken to avoid underfeeding nutrients especially protein when limiting feeding boars (< 2 kg/hd/d).

Replacement Gilts:

It is reasonable to expect that replacement gilts’ needs are different from the pigs, which are being raised for slaughter. Finishing diets are designed for cost efficiency and rapid growth, which may not provide adequate nutrients for the development needed to prepare the breeding female for a long life of pig rearing. Diets formulated specifically for the development of replacement gilts should contain higher concentrations of vitamin A, vitamin E, calcium (Ca), phosphorus (P), selenium (Se), copper (Cu), and zinc (Zn) compared to market hogs to ensure higher body reserves of specific nutrients that are needed during future reproductive purposes and to enhance the passive immune response. Dietary concentrations of Ca and P need to be high enough to allow for maximum bone mineralisation and can be later mobilised if foetal and lactation demands exceed dietary nutrient intake.

Reproductive performance and longevity can be improved by feeding higher Ca and P concentrations to gilts. The recommended dietary nutrient requirements for replacement gilts are a minimum of 0.8% Ca (18 g daily), 0.7% total P (15 g daily), and 0.4% available P. If the protein and amino acid requirements are not met during gilt development, a delay in the age at which the gilt reaches puberty may occur. Most finishing diets have adequate concentrations of protein (15 % crude protein) and amino acids (0.7% total lysine or 25 g daily) to satisfy the developing gilt. Replacement gilts should receive limited feed from the time they reach 110 – 115 kg until about 2 weeks before mating to improve the sow’s longevity. It is well established that flushing (feeding high amounts of feed for a short time before mating) increases ovulation rate and litter size compared to restricting feed intake during oestrus. To flush females, feed intake can be increased to 3 – 4 kg per head daily for 2 weeks before breeding. Typically, gilts are bred at 140 – 150 kg or after their third oestrus.

The nutrient requirements of boars and replacement gilts on an as-fed basis.

Item %	Development Phase
Item %	Early	Mid	Late	Mature
Protein	22	20	18	16
Lysine	1.2	1.1	1	0.85
Ca	0.95	0.85	0.8	0.9
Tp	0.75	0.65	0.75	0.8
Ap	0.49	0.4	0.49	0.5
Where: TP – Total Phosphorus AP – Available Phosphorus

Gestation:

After the female is bred, the nutrition and feeding program becomes more variable and should be based on each sow’s body composition. The body fat content should be closely monitored because either excessive body condition or low-fat reserves will be detrimental to the subsequent reproductive cycle. Therefore, the gestation diet needs to control weight gain as well as provide enough nutrients to support foetal development.

Gestating females are limit-fed (2 – 2.5 kg of feed per day and an extra 0.5 – 1 kg if housed outside) to minimise excessive weight gain. First parity gilts should receive an extra 10 – 15 % (2.5 – 3 kg of feed per day) to compensate for their physical protein growth needs. Older sows (parity > 5), that are large framed have a higher maintenance requirement along with a lower body fat content and could require a higher feed intake. However, over-conditioned females will ovulate fewer eggs and have smaller litter sizes.

A gestation diet containing a 14% crude protein (0.7% total lysine, 0.9% Ca, 0.8% total P, and 0.45% available P) will be adequate for first parity females that are compensating for both muscle and foetal growth, however, older (parity 2 and greater) females probably only require a 12 to 13 % crude protein diet (0.6% total lysine, 0.9% Ca, 0.8% total P, and 0.45% available P).

Another good nutritional management practice enhancing lactation feed intake is to transition the gestating female over to the lactation diet 1 week before farrowing.

Weaning to Rebreeding:

Lactation feed intake and getting sows back onto feed during pre-breeding is important in reducing wean-to-oestrous intervals. At the time of weaning, there is a dramatic reduction in feed intake and body weight as milk production stops causing mammary tissue to dehydrate. Typically, sows with a low body-fat content will frequently have a longer weaning to rebreeding interval, a low lactation feed intake is perhaps more responsible for poor breeding performance after weaning than is low body-fat content. It is important to reach a feed consumption level of up to 1 – 1.5 kg per day so there is no interference with mechanisms such as hormone excretion from the intestinal tract.

Feed intake and fibre are two factors that seem to be key factors helping limit the inhibitory effect of feedback hormones being reabsorbed from the intestinal tract. Sows in a catabolic state do not reverse this metabolic process quickly. Feeding high protein concentrations during this period (ex. Lactation diet) will likely have little or no effect other than a waste of costly amino acids. Feeding a gestation diet containing some fibre and encouraging weaned sows to consume as much as possible helps eliminate excreted hormones from the intestinal tract.

The energy requirements of rebreeding sows.

Life mass (kg)	Daily Gain (g)	Daily Intake (kg)	ME/MJ
20	500	0.97	12.6
30	625	1.40	18.2
50	790	2.10	27.5
70	790	2.65	35.0
90	800	3.10	40.0

The energy requirements of pregnant sows.

Begin Mass	MJ/DAY
Begin Mass	Week 1 – 12	Week 13 – 16
135	22.0	23.0
160	25.0	28.0
200	30.0	32.0

Lactation:

During the relatively short lactation period, today’s high-producing, maternally lean sows are expected to recover from farrowing, maximise milk production, eat 10 kg + of feed per day and rebreed before traditional sows were typically weaned. The lactating sow produces 7.5 – 15 kg of milk per day resulting in daily nutrient requirements that are about 3 times higher than during gestation. For highly, prolific sows, nutrients from body tissue reserves and feed are used to support lactation. This results in loss of body weight (negative nutrient balance).

Excessive body weight loss can lead to short-term reproductive problems such as extended weaning-to-oestrus interval and smaller subsequent litter size. Long-term problems include a higher culling rate of the sow herd resulting in a low average parity; reduced pigs weaned per reproductive lifetime and higher costs per pig produced. Increasing feed intake and/or increasing nutrient concentration in the lactation diet can minimise the amount of body weight loss and maintain high milk production, which will subsequently improve reproductive performance. Swine producers need to ensure that maximum lactation feed intake is achieved by having sow cards that allow daily feed intake to be recorded. This is especially important when more than one person does the sow feeding. These high-producing, maternally lean females lose more muscle and less fat than low-lean genotype lines.

When producers switch from feeding 2 times per day to 3 times per day, an increase of 10 – 15% in feed intake is observed. This practice of feeding smaller amounts of feed more frequently is especially beneficial during the summer months as the increase in body temperature that occurs after a sow consumes a meal won’t be as big when 2.5 kg of feed is fed versus 3 kg of feed.

The step-up feeding program is only a baseline schedule to follow and can be adapted to satisfy each swine operation. An example is shown in the following Tables for first parity and multiparous females, respectively. If there is some feed (> 1 kg) left from the previous meal, no feed should be added, or the old feed can be removed and offer the same amount of feed as fed at the last meal. Many other factors limit lactation feed intake such as water accessibility (water flow should be 1 500 ml/min), type of feeder used, and ventilation rates (poor air quality)

Feeding program for genetically lean “first parity gilts” during lactation.

Day of Lactation	Kilogram of Feed
Day of Lactation	AM	PM	Total/Day
Day 1	2	0	4
Day 2	1.5	1.5	3
Day 3	2	2	4
Day 4	2.5	2.5	5
Day 5	3	3	6
Day 6	3.5	3.5	7
Day 7 to wean	4	4	8

Feeding program for genetically lean “multiparous sows” during lactation.

Day of Lactation	Kilogram of Feed
Day of Lactation	AM	PM	Total/Day
Day 1	3	0	3
Day 2	2	2	4
Day 3	2.5	2.5	5
Day 4	3	3	6
Day 5	3.5	3.5	7
Days 6 and 7	4	4	7
Day 8	4.5	4.5	9
Day 9 to wean	5	5	10

Overall, good lactation performance is not just a post-farrowing process but encompasses the entire reproductive cycle. Success in pork production necessitates an efficient and well-managed breeding herd program. Today’s prolific, high-lean sow may be tomorrow’s average sow. Therefore, knowing how to feed and manage the breeding herd, whether today or tomorrow, will enable swine producers to be competitive and successfully meet the challenges encountered.

Objectives at Weaning:

The objective should be to obtain a quality piglet at weaning so that it will transition to the start at this stage and have good technical and economic performance. A quality piglet will be one that:

Is of adequate age (minimum 21 days) and weight at weaning (minimum 6 kg on average with very little variability concerning the average of the group).
Optimum health status.
High intake capacity (average daily intake (ADI) and high average daily gain (ADG).
Adequate maturity and intestinal health.

Weaning weight is a very important factor as it is related to mortality in the later rearing and fattening phases (see Figure 1.39).

Percentage of cumulative mortality throughout the rearing and fattening period as a function of piglet weaning weight.

Regular and high intake of the piglet is necessary. Some of the strategies to achieve these objectives are:

Supplying piglets with the same type of feed as they consume in the final maternity phase.
High-quality diets with tasty and palatable ingredients.
Handle the feed correctly, administering it several times a day, having extra dishes, working with mash in the first days, and applying water with the rehydrating agent in round hoppers.
The water of biochemical and bacteriological quality is supplied at suitable temperatures.
Climatic comfort – temperatures at a weaning of 28 °C.

The later the piglet is weaned, the more prepared the piglet is generally. When an immature piglet is weaned, digestive problems or the so-called “post-weaning syndrome” (diarrhoea, dehydration, loss of body condition and increased mortality) usually occur.

Related to these concepts we can find four situations summarised in the following Table.

A summary of situations at weaning.

	Low Weight at Weaning	High Weight at Weaning
Inadequate Physiological Age	Situation 1: Very Unfavourable	Situation 2: Unfavourable
Adequate Physiological Age	Situation 3: Favourable	Situation 4: Optimal

Situation 1: Very Unfavourable

This is the most unfavourable situation, as the piglets are not only immature but also underweight. These piglets are very sensitive to the lack of “thermal comfort”. They have an immature digestive system so they need highly digestible ingredients, and the feed intakes achieved at weaning are extremely low so they will need nutrient-dense diets.

Situation 2: Unfavourable

Piglets with adequate weaning weights but inadequate intestinal maturity. This situation usually occurs with the heaviest piglets in the litter, so-called strict sucklers, who do not recognise the new food source at weaning, leading to a period of anorexia and weight loss. In this situation, it is key to get as many piglets as possible to start solid feed early with strategies such as creep feed. It is recommended:

Use of mash or wet feed.
Stimulate exploratory behaviour by feeding small amounts of feed several times a day.
Stimulate water consumption.
Use high-quality and digestible diets and feed supplements to encourage intake.

Solid feed (creep-feed) is advised during lactation because its consumption familiarises piglets with the type of diet they will receive in the future and, in turn, encourages their maturation and enzymatic capacity of the intestines.

Situation 3: Favourable

In this case, these are piglets with low weight, but adequate physiological age. Normally the smaller animals in each litter are more accustomed to consuming and exploring the feed to satisfy the nutritional intake that they do not find in the mother’s milk. Thus, when transitioning, they are already accustomed to solid feed intake and show a better adaptation.

With this type of piglets, the main disadvantage is that they are very sensitive to environmental comfort, as they have low body reserves of

Situation 4: Optimal

In this case, these are piglets with high weaning weights and adequate physiological age or intestinal maturity.

These piglets will have a more favourable starting situation than the rest, since, if the environmental conditions and facilities are adequate, and the feed is of good quality, they will have a good start at weaning.

Phase Feeding of Weaners:

Based on the development of weaned piglets’ digestive system, three diets are typically fed during the nursery period.

The feeding duration of each phase will vary according to weaning age. Phases 1 and 2 to pigs no longer than 42 d of age. This is due to the high costs of dairy products and speciality proteins in early nursery diets. The nursery feeding program corresponds to approximately 10 – 15% of the total feed cost to produce a pig.

Phase 1 – Weaning to ~7.5 kg.

Feeding newly weaned pigs requires a diet with greater inclusions of highly digestible carbohydrates and protein sources to maximise feed intake while matching their digestive capabilities. This diet typically has a greater cost per ton than subsequent phases.

Pigs that have been weaned show a temporary hypersensitivity to soybean meal. A maximum of 20% SBM is recommended during this phase to facilitate adaptation to simpler meals with increased SBM in later phases. The majority of protein in early nursery diets is normally derived from plant sources, however feed-grade amino acids and animal protein sources can reduce the proportion of soybean meal. The usage of soy protein concentrates up to 14% and fermented soybean meal between 6% and 15% has no negative effect on development or intake. Fish meal can be introduced in early nursery diets at a 3 – 6% level to boost feed consumption. Be aware that fish meal quality can vary substantially between sources, with mineral and lipid levels serving as an indicator of fish meal’s feeding value (e.g., maximum 20% ash and minimum 7.5% fat.)

Phase 2 – 7.5 to 11.5 kg.

Reduce diet complexity in phase 2, with diets comprised of a grain source, soybean meal, and lower levels of lactose and speciality protein sources. Lactose levels are normally reduced to roughly 7% of the diet, whereas SBM levels are typically increased to a maximum of 28%. Due to the abundant availability and lower cost of feed-grade tryptophan, the valine and isoleucine speciality proteins in this diet can be lowered or eliminated without a significant impact on the bottom line.

Phase 3 – 11.5 to 22.5 kg.

The phase 3 diet is primarily comprised of a grain source and soybean meal with no inclusion of lactose or speciality protein sources. It contains similar ingredients to grow-finish pig diets. Nursery growth potential is the greatest during this phase and it is crucial to meet their nutrient needs, especially Lys.

Formulating Grow-Finish Diets:

The steps in diet formulation for finishing pigs include:

Determine the optimal Lys: calorie ratio.
Determine the most economical energy level. Energy is the major cost of any grow-finish diet and does affect growth performance significantly.
Determine the ratio for the other amino acids.

The dietary tryptophan to Lys ratio has a significant impact on feed intake and growth rate. Depending on a system’s specific scenario of a fixed time or fixed weight, varying the tryptophan to Lys ratio could greatly impact profitability.

Using the fibrous by-products from corn or wheat processing in grow-finish diets is a common practice to reduce feed costs. However, greater dietary fibre levels may influence the optimal levels of threonine. Mathai et al. (2016) reported the threonine to Lys ratio for maximising ADG increased from 66 to 71% when dietary NDF levels increased from 8.3 – 16.6% in 25 – 50-kg pigs.

Determine the phosphorus level.

Phosphorus is the third most expensive nutrient in swine diets. Phosphorus is required for growth, lean tissue deposition, and bone mineralisation.

Set Levels of calcium, vitamins, trace minerals, salt, and other ingredients.

The ratio between calcium and phosphorus generally determines dietary calcium levels. The analysed Ca to analysed P ratio that maximised ADG for 26 – 127 kg pigs was 1.63:1 and 1.38:1 when diets were with or without 1000 FYT/kg phytase, respectively.

In addition to the above five steps of formulating grow-finish diets, adjusting diet formulations based on seasonal variation of performance and market pricing could help maximise profitability.

Feeding values of growing pigs and breeding sows.

Protein and Amino Acids (Animals with 16 MJ ME/kg DM)
	Growing Pigs on Live Mass		Breeding Sows
	20 – 50 kg	50 – 90 kg	Breeding Sows
Crude Protein (% of DM)	18	16	16
Amino Acids (% of DM)
Lysine	0.95	0.75	0
Methionine and Cysteine	0.65	0.65	0
Tryptophan	0.18	0.18	0
Vitamins
A (UI/ kg Feed)	1 600	1 900	3 600
D (UI/kg Feed)	230	230	160
E (UI/kg Feed)	1.5	1	0
Thiamine (mg/kg)	1.5	1.5	1.5
Riboflavin (mg/kg)	2.5	2.5	3
Nicotinic acid (mg/kg)	12	12	12
Pantothenic acid (mg/kg)	10	10	10
Propionic Acid	2	2	1
B12 (micro/kg)	10	10	15
Choline (mg/kg)	850	850	0
Minerals
Calcium	0.8	0.06	0.6
Phosphorus	0.6	0.5	0.5
Iron	75	60	60
Zinc	80	60	60

B. The Value of Different Feeds in Pig Rations

Traditionally, fish meal is used as an animal protein supplement and maize meal serves as the foundation of the energy portion of pig feeds. Due to its flavour and low fibre content, maize meal is widely accepted. and for the fish meal, which serves to supplement the maize meal’s inadequate amount of amino acids. Despite the widespread use of fish meals and maize meals, there are drawbacks, especially when it comes to the final rations.

It was found that the corn oil in corn meal has the tendency to develop soft fat in pigs and the fish meal has the tendency to leave an unfavourable taste. Barley is the most favourable feed seeing that gives a compact fat layer. and carcass meal or plant-derived protein supplements as an alternative to fish meals. in the final grower’s rations.

Wheat bran and pollards are two popular feed commodities which are relatively cheap. but which also contain protein and are rich in phosphorus and B- vitamins. Care should be taken that these millings reject products should not be incorporated in rations with higher than 20% of the ration because of the high fibre content these products consist of. Lucerne meal also has its benefits but should be added at a maximum rate of 10% to a given ration.

Feeding Management of Sheep

Feeding management of sheep.

Sheep are primarily fed on pastures, or what is known as “field grazing,” where they require shelter, enough food, and clean water. Although the sheep mostly eat the roughage found in pastures, they occasionally receive supplemental feed like maize and hay. For optimum growth and production, sheep require both water and energy (carbohydrates and fats). Make sure sheep have access to appropriate shelter, enough fresh drinking water, and food in sanitary feeding troughs at all times. Pasture is the main source of feed for sheep and its also the one that is economically viable business-wise.

Since sheep get their nutrition from the pastures they graze on or from the feed when they are housed in intensive farming systems, feeding is a crucial part of sheep farming. Protein, energy (such as fats and carbohydrates), vitamins, and freshwater are all necessary components of a balanced diet.

A. The Year-Round Sheep Nutrition

Sheep nutrition requirements include six nutrients (water, protein, fat, carbohydrates, minerals, and vitamins) and energy (received from the protein, fat, and carbohydrates consumed).

Ewe nutrition at every stage.

Ewe nutrition needs vary more throughout the year than rams due to the changes in their reproductive status. Five main reproductive stages determine ewe nutritional requirements, including maintenance, breeding, early gestation, late gestation, and lactation.

Feeding ewes during maintenance.

The lowest ewe nutrition and energy requirement are during maintenance. For a typical sheep flock, this occurs after lambs are weaned from the ewe and before the ewe is rebred. In an accelerated lamb program, the ewe may never be in maintenance, or in an early weaning program, maintenance may last 20 weeks. Although ewes in maintenance are only maintaining themselves, it does not mean nutrition is not important. Usually, the ewe in maintenance can meet her energy and protein requirements with pasture or hay alone. Depending on the quality of the forage and the soils on which it was grown, both vitamins and minerals would need to be supplemented through a sheep mineral and vitamin mix offered free choice.

Sheep breeding season.

Two to four weeks before the sheep breeding season and two to four weeks into the breeding season, ewe nutrition and energy intake can be increased to help optimise ovulation rate and the opportunity for multiple births. This period is called flushing. Flushing can be accomplished by placing ewes on high-quality pasture or adding energy in the form of a grain mix or sheep feed pellets.

Early gestation ewe nutrition.

Following the sheep breeding season, bred ewes can be placed on a sheep nutrition program to maintain their weight. Although ewes are bred, the foetuses are only growing a small amount during the first and second trimesters. Ewes can be fed on pasture or if in confinement, a good quality grass hay. In both situations, ewes should be fed a sheep mineral and vitamin mix to complement the nutrient content of the forages fed. The ewe’s energy requirements increase slowly over early pregnancy and rapidly in the last 50 days before lambing. Lactation greatly increases energy requirements, and peaks at around 25 days after lambing. As ewes enter late gestation, the greatest growth of the foetuses occurs and ewe nutritional requirements and energy needs increase. During this period, a. (100 kg) ewe, pregnant with a single lamb, will have a 50% and 71% increase in energy and protein requirements, respectively, compared to maintenance requirements. Ewes with twins or triplets with energy and protein requirements 25 – 41% greater than ewes carrying a single lamb. The size of the ewe and the number of lambs will determine how much supplemental energy and nutrients are required along with good quality hay to meet the ewe’s nutritional requirements. Ewes in late pregnancy also have a higher requirement for protein and should be fed a diet containing more than 15% crude protein.

The energy requirements (megajoules per head per day) for maintaining ewes during pregnancy in condition score 3.

Days Pregnant	Small Frame Ewe (Single)	Small Frame Ewe (Twin)	Medium Frame Ewe (Single)	Medium Frame Ewe (Twin)	Large Frame Ewe (Single)	Large Frame Ewe (Twin)
Dry	7.7	7.7	8.3	8.3	9.9	9.9
50	8	8	8.6	8.7	10	10.2
70	8.3	8.4	8.9	9.1	10.4	10.7
120	9.8	11.2	10.9	12.4	12.7	14.6
Lambing	11.8	13.7	12.8	14.7	14.9	17.1

The energy requirements (megajoules per head per day) for maintaining ewes during lactation in condition score 3.

Days Pregnant	Small Frame Ewe (Single)	Small Frame Ewe (Twin)	Medium Frame Ewe (Single)	Medium Frame Ewe (Twin)	Large Frame Ewe (Single)	Large Frame Ewe (Twin)
10	17.3	21.7	19.2	24	22.4	28.1
20	19.2	24.6	20.6	26.2	25	31.8
40	17.2	21.7	19.1	24.5	22.4	28.2
70	7.7	7.7	8.3	8.3	9.9	9.9

Feeding ewes post lambing.

After the ewe lambs, lactation is the period of the reproductive cycle with the greatest ewe nutritional requirements. During early lactation, the first 8 weeks after lambing, the ewe produces the most milk. For a 100 kg. ewe nursing a single lamb, the energy and protein requirement will increase another 35% and 90%, respectively, compared to ewe nutritional requirements during late gestation. The ewe with twins and triplets will have greater energy and nutrient requirements than the ewe nursing a single lamb. In most cases, supplemental feed will be needed along with a high-quality forage to meet the elevated ewe nutrient demand.

When lambs are one week old, it is a good time to start offering creep feed, so lambs learn to eat dry food and provide extra energy and nutrients. At first, lambs will only nibble the creep feed, but as they get older, they will eat more and more. Ensure the creep feed is in an area that prevents the ewes from accessing it and keeps the feed fresh and always available. Providing a creep feed helps the lambs adapt to eating only dry food upon weaning.

The best feed for rams.

Breeding rams may only have one job, one or two times a year to do, but what happens the rest of the year is important to their success. During a 45-day sheep breeding season, rams can lose up to 12% of their body weight. Rams will need to be fed a diet to regain body condition lost during the breeding season and to achieve a body condition score of 3.5 to 4, out of 5, before the next sheep breeding season. Yearling rams are still growing, so they too may need extra feed.

Ewe nutrition includes water.

One sheep nutrition need that is often overlooked is water. Water is a critical nutrient to assist with nutrient transport, heat dissipation and milk production. Allow the sheep flock free access to clean fresh water always. As with water, it is always good to provide a sheep mineral and vitamin mix to supplement and balance the forages in the diet being fed.

Feeding and wool production.

Regarding the effect of feeding on wool production, two factors play a role namely:

Feeding before and after birth would determine how many wool follicles would be formed to produce wool in the future.
The influence of immediate feeding status on the tempo of wool growth. and the quality of the wool.

It was revealed that low-condition lambs whose mothers had little nutrition before and after birth had fewer and slower wool-producing follicles. For instance, 80% of the follicles in the lambs of ewes on an appropriate feeding programme were functional, compared to less than 20% in the case of ewes on a low feeding programme.

Wool follicles and how wool grows.

Wool growth can vary over a four-fold range due to changes in nutrient supply. The major nutritional limitation to wool growth is the amount and composition of amino acids available to wool follicles. ‘Maximum’ rates of wool growth can be attained on maintenance intakes of energy with about 150 g of ideal protein available for intestinal digestion. A mixture of essential amino acids given via the abomasum is as effective as protein for enhancing wool growth. The sulphur-containing amino acids (cysteine and methionine) and lysine are particularly important for wool growth.

Because wool proteins are rich in cysteine, an adequate supply of cysteine is needed by the wool follicles to sustain wool growth. An important function of methionine is the provision of cysteine via the transsulfuration pathway; it can also be catabolised via the transamination pathway. At levels of methionine normally absorbed by sheep, it is concluded that about three-quarters of the methionine-S is converted to cysteine-S. Experiments with mixtures of amino acids given via the abomasum, and with analogues of methionine (ethionine and methoxamine), have indicated a specific role for methionine in the control of wool growth, most probably as a methyl donor or a precursor for polyamines via S-adenosylmethionine. Evidence is presented that interference with the synthesis of polyamines can influence wool growth.

Many vitamins and trace elements are necessary for the process of wool growth. Two vitamins, folic acid, and pyridoxine, may be especially important because of their involvement in the metabolism of methionine and polyamines. Copper and zinc function directly in the process of wool growth; copper is involved in keratinisation with zinc being specifically required by rapidly proliferating tissues.

B. Feed Flow for Sheep for Maintenance and Production Requirements

When planning the feed flow for an operation it is first necessary to determine the production cycle of the animal. In this way, it becomes possible to ascertain the general requirements of the herd over time. This can then be matched to the provision of nutrients from the natural pasture at that same period and shortfalls can be determined.

The following important periods need special attention during the production cycle of a female small stock animal:

Dry: This is the period between weaning the offspring and being bred. During this period, the female is regaining the weight lost while nursing the offspring. She must reach a satisfactory condition score before being bred again. However, the nutrient demand here is the lowest.
Mating: Flushing can be used to increase the ovulation rate. Flushing involves providing supplementary feeding 3 weeks before the male is introduced, and 3 weeks after they were introduced. If the herd is on the veld, flushing can be accomplished by putting the females onto lush pasture, or by feeding pellets or grain.
Early gestation (1st 100 days): Foetal growth is slow during this period. A maintenance diet is enough, and no ill effects will be found if the females are grazing veld.
Late gestation (last trimester): Foetal growth is very rapid, and the foetuses gain 70% of their birth weight in these 50 days. Protein and energy requirements increase dramatically. In adverse weather conditions, the farmer should provide adequate feed for the pregnant females, to avoid losing offspring or having offspring born in poor conditions. During the 5th month of the gestation period, the daily gains of the female should range from 0.1 – 1.2 kg.
Lactation: This is the most critical period. The female’s requirements must be met, as the production of sufficient milk of good quality ensures that the offspring are healthy, grow fast, and at the end of the day they produce more meat, which means more money in the farmer’s pocket.
Active growth stage of the young animal: A high-quality feed should be fed to young animals because the requirements for growth are high and the rumen capacity at this stage is still a limiting factor. Poor nutrition during this stage can lead to permanent stunting of the animal. Differences of nearly 20% in mature body mass were obtained as a result of differences in nutritional treatment before four months of age. Also, the influence of pre-and postnatal treatments was additive. This means that if the mother is fed well in the last few weeks of pregnancy, and the young that are born are strong, then, if the young are also fed well up to weaning, the final result will be even stronger and healthier offspring.

C. Sheep Flock Nutritional Requirements

Healthy Dohne Merino lamb.

Energy.

Energy makes up the largest portion of the diet and is usually the most limiting nutrient in sheep diets. Carbohydrates, fat, and excess protein in the diet all contribute towards fulfilling the energy requirements of sheep. Carbohydrates are the major sources of energy. Concentrates (grain) contain starch, which is a rich source of energy. Forages contain fibre or cellulose, which is not as rich in energy as starch. The major sources of energy in a sheep’s diet are pasture and browse hay, silage, and grains.

Meeting energy requirements without over or underfeeding animals is one of the farmer’s biggest challenges. An energy deficiency is the most common nutritional deficiency in sheep. An energy deficiency will manifest itself in many ways. In growing animals, an early sign of energy deficiency is reduced growth, then weight loss, and ultimately death. In reproducing females, early signs of an energy deficiency are reduced conception rates, fewer multiple births, and reduced milk production.

With restricted energy consumption, wool growth slows, fibre diameter is reduced, and weak spots (breaks) develop in the wool fibre. An energy deficiency reduces the functioning of the immune system. Undernourished sheep are more susceptible to diseases, especially gastrointestinal worms.

Excess energy consumption can cause problems in sheep, too. Extra energy is stored as fat (adipose tissue). Gross excesses in adipose tissue impair reproductive functioning in rams and ewes. During late gestation, fat ewes are more prone to ketosis (pregnancy toxaemia) and dystocia (difficult birth). Fat lambs do not gain muscle efficiently, and they are undesirable to most consumers.

Energy in the ration is quantified in many ways. The simplest measure is TDN, which is the acronym for “total digestible nutrients”. Metabolisable energy (ME) and net energy (NE) values are more accurate measures of energy in a sheep’s diet. TDN is usually used to formulate rations for breeding animals, while the net energy system is often used to calculate diets for growing lambs.

Supplementary feeding of sheep with grain, hay, or silage is necessary when pastures or roughage are deficient in energy and protein.

Protein.

Protein is usually the most expensive part of the diet. Since the rumen manufactures protein from amino acids, the quantity of protein is more important than the quality of protein in a sheep’s diet. Protein requirements are highest for young, growing lambs who are building muscle, and lactating ewes who are producing milk proteins.

The most common protein supplement for sheep is soya bean meal. Other less common sources include sunflower meal, cottonseed meal, whole cottonseed, whole soya beans, peanut meal, canola (rapeseed) meal, fish meal, and alfalfa pellets. In most countries, it is illegal to feed meat and bone meal derived from other ruminants. Legume hays, when they are harvested in the early to mid-bloom stage are intermediate sources of protein.

Though levels vary, grains are usually low in protein. Urea is the most inexpensive source of protein or dietary nitrogen. Urea is converted to protein in the rumen. It has an equivalent crude protein value of 280%. It needs to be carefully incorporated into sheep rations and should not be included in creep rations.

Protein blocks are the most expensive way to provide supplemental protein to pastured animals, but they save labour. The hardness of the block regulates intake by the sheep. Excess protein is an expensive and inefficient source of energy. It can have a detrimental effect on animal health, as excess protein is converted to urea and ammonia. Animals overfed with protein excrete more nitrogen in their urine and faeces.

Minerals.

Sixteen (16) minerals have been classified as nutritionally essential in sheep diets:

Macro-minerals are required in large quantities. They include sodium (Na), chloride (Cl), calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K), and sulphur (S).
Micro-minerals (also called trace minerals) are required in small quantities. They include iodine (I), copper (Cu), iron (Fe), manganese (Mn), zinc (Zn), molybdenum (Mo), cobalt (Co), selenium (Se), and fluoride (Fl).

Salt.

Salt (sodium [Na] and chloride [Cl]) has an important regulatory function in the body. Inadequate salt intake can decrease feed and water intake, milk production, and growth of lambs. Animals desiring salt may chew on wood and/or lick dirt. They are also more likely to consume poisonous plants. When adding salt to mixed rations, it is customary to add 0.5% to the complete diet or 1% to the concentrate portion. Salt is sometimes used to limit the intake of free-choice mineral mixes. It can be used to regulate the intake of feed.

Calcium and phosphorus.

Calcium (Ca) and phosphorus (P) are interrelated in the development and maintenance of the skeleton. Deficiencies may result in rickets. An imbalance of Ca and P in the diet can cause urinary calculi in male sheep, especially wethers. The calcium in most forages is usually adequate to meet the needs of sheep. Deficiencies of calcium most often result when high-grain diets are fed, as cereal grains and oilseeds are high in phosphorus and low in calcium. The ratio of calcium to phosphorus in the sheep’s diet should be at least 2:1.

Vitamins.

Sheep require vitamins A, D, and E. Vitamin A is absent in most plant material but is synthesised from beta-carotene. Vitamin D is required to prevent rickets in young animals and osteomalacia in older animals. B vitamins are not required in the diets of ruminants because they are synthesised in the rumen. Vitamin K is essential for blood clotting. Dietary supplementation is usually not necessary.

Fibre.

Fibre adds bulk to the diet and keeps the sheep’s rumen functioning properly by increasing rumination and salivation. Most ruminant nutritionists agree that sheep should always have roughage in their diets, at least 453,6 grams per head per day. Sheep that do not consume adequate forage may chew on wood or wool.

D. Implementing a Nutritional Program for Sheep

To meet the nutritional requirements of each animal at its particular stage of life, producers must combine feed ingredients into the least costly but most efficient ration. The following Tables provide estimates of the daily nutrient needs of sheep.

Daily Nutrient Requirements of LAMBS:

a	=	To convert dry matter to an as-fed basis, divide dry matter values by the percentage of dry matter in the particular feed.
b	=	One 0.5 kg TDN (total digestible nutrients) = 0.91 Mcal DE (digestible energy).
c	=	These are the maximum weight gains expected.
d	=	These lambs are intended for breeding, so maximum weight gains and finish are of secondary importance.
e	=	Values are applicable for ewes in moderate conditions. Fat ewes should be fed according to the next lower weight category, and thin ewes at the next higher weight category. Once the desired or moderate weight condition is attained, use that weight category through all production stages.

Daily nutrient requirements per lamb.

Early-Weaned Lambs – Moderate Growth Potential
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
11	0.22	0.55	5	0.19	0.9	0.004	0.002	470	10
22	0.3	1.1	5	0.185	1.8	0.006	0.003	940	20
33	0.33	1.45	4.3	0.21	2.2	0.0075	0.004	1410	20
44	0.38	1.55	3.8	0.22	2.6	0.009	0.004	1880	22
55	0.33	1.65	3	0.2	2.6	0.008	0.004	2350	22
Early-Weaned Lambs – Rapid Growth Potential
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
22	0.28	0.65	6	0.175	1.1	0.006	0.003	470	12
44	0.33	1.3	6	0.23	2	0.007	0.003	940	24
66	0.36	1.55	4.7	0.24	2.4	0.008	0.004	1410	21
88	0.44	1.55	3.8	0.26	2.5	0.009	0.005	1880	22
110	0.47	1.85	3.4	0.28	2.8	0.011	0.0075	2350	25
132	0.34	1.85	2.8	0.26	2.8	0.009	0.003	2820	25
Lambs Finishing – Age 4 – 7 Months
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
66	0.32	0.725	2.15	0.11	2.1	0.004	0.002	1410	20
88	0.3	0.875	2	0.10	2.7	0.004	0.002	1880	24
110	0.28	0.875	1.63.2	0.09	2.7	0.003	0.002	2350	24
Replacement Ewe Lambs
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
66	0.25	1.3	4	0.21	1.7	0.007	0.006	1410	18
88	0.2	1.55	3.5	0.19	2	0.0065	0.006	1880	21
110	0.13	1.65	3	0.15	1.9	0.006	0.005	2350	22
132	0.11	1.65	2.5	0.15	1.9	0.005	0.005	2820	22
154	0.11	1.65	2.1	0.14	1.9	0.005	0.006	3290	22
Replacement Ram Lambs
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
88	0.37	2	4.5	0.27	2.5	0.0085	0.004	1880	24
132	0.35	2.65	4	0.29	3.4	0.009	0.005	2820	26
176	0.32	3.0	3.5	0.29	3.9	0.009	0.005	3760	28
220	0.28	3.3	3	0.28	4.2	0.009	0.005	4700	30

Daily Nutrient Requirements of EWES:

Daily nutrient requirements per ewe.

Ewes on Maintenance Feeding
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
110	0.01	1.1	2	0.15	1.2	0.002	0.002	2350	15
132	0.01	1.2	1.8	0.155	1.3	0.003	0.0025	2820	16
154	0.01	1.3	1.7	0.125	1.5	0.003	0.003	3290	18
176	0.01	1.45	1.6	0.13	1.6	0.003	0.003	3760	20
198	0.01	1.55	1.5	0.14	1.7	0.003	0.003	4230	21
Flushing – Two Weeks Before Breeding and First Three Weeks of Breeding
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
110	0.11	1.6	3.2	0.16	2.1	0.006	0.003	2350	24
132	0.11	1.8	2.8	0.17	2.2	0.006	0.003	2820	26
154	0.11	2	2.6	0.18	2.3	0.006	0.004	3290	27
176	0.11	2.1	2.4	0.18	2.5	0.006	0.004	3760	28
198	0.11	2.2	2.2	0.19	2.6	0.006	0.004	4230	30
Nonlactating – First 15 Weeks of Gestation
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
110	0.07	2.6	2.4	0.25	1.5	0.006	0.005	2350	18
132	0.07	2.9	2.2	0.27	1.6	0.007	0.005	2820	20
154	0.07	3.1	2	0.29	1.7	0.008	0.006	3290	21
176	0.07	3.3	1.9	0.31	1.8	0.008	0.007	3760	22
198	0.07	3.5	1.8	0.33	1.9	0.009	0.008	4230	24
Last 4 Weeks of Gestation – 130 – 150% Lambing Rate Expected
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
110	0.2	1.75	3.2	5.45	60	0.18	0.14	1214	7
132	0.2	1.85	2.8	5.4	59.5	0.17	0.15	1378	7
154	0.2	2	2.6	5.3	57.5	0.17	0.15	1490	7
176	0.2	2.1	2.4	5.3	57.1	0.16	0.15	1619	7
198	0.2	2.2	2.2	5.4	56.8	0.16	0.16	1738	7
Last 4 Weeks of Gestation – 180 – 225% Lambing Rate Expected
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
110	0.25	1.85	3.4	5.45	64.8	0.19	0.095	1148	7
132	0.25	2	3	5.6	65	0.16	0.1	1275	7
154	0.25	2.1	2.7	5.6	66.7	0.2	0.12	1416	7
176	0.25	2.2	2.5	5.5	65.9	0.25	0.15	1545	7
198	0.25	2.3	2.3	5.5	65.2	0.22	0.15	1663	7
First 6 – 8 Weeks of Lactation – Suckling Singles
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
10	-0.03	2.3	4.2	3.7	65.2	0.22	0.14	923	7
132	-0.03	2.55	3.8	3.33	64.7	0.19	0.135	1000	7
154	-0.03	2.55	3.6	3.33	65.5	0.18	0.135	1082	7
176	-0.03	2.8	3.2	3.3	64.9	0.18	0.14	1193	7
198	-0.03	2.9	3	3.3	64.4	0.18	0.14	1296	7
First 6 – 8 Weeks of Lactation – Suckling Twins
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
110	-0.07	1.35	4.8	4	64.1	0.23	0.15	943	7
132	-0.07	1.4	4.3	3.9	64.9	0.20	0.15	1052	7
154	-0.07	1.55	4	3.7	64.5	0.20	0.15	1129	7
176	-0.07	1.65	3.8	3.5	65.1	0.19	0.15	1212	7
198	-0.065	1.75	3.6	3.5	65.7	0.19	0.15	1285	7
Last 4 – 6 Weeks of Lactation – Suckling Singles
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
110	0.05	1.75	3.2	5.45	60	0.19	0.14	1 214	7
132	0.05	1.8	2.8	5.4	59.5	0.18	0.15	1 378	7
154	0.05	2	2.6	5.25	57.5	0.18	0.15	1 490	7
176	0.05	2.1	2.4	5.25	57.1	0.17	0.15	1 619	7
198	0.05	2.2	2.2	5.3	56.8	0.16	0.16	1 738	7
Last 4 – 6 Weeks of Lactation – Suckling Twins
Body Weight (kg)	Avg. Daily Gain (kg)	Dry Matter (kg/head)	% Body Weight	Total Protein (kg)	TDN	Calcium (kg)	Phosphorous (kg)	Vit A (IU)	Vit E (IU)
110	0.1	2.3	4.2	7.3	65.2	0.21	0.14	924	7
132	0.1	2.5	3.8	6.8	64.7	0.19	0.13	1 000	7
154	0.1	2.75	3.6	6.7	65.5	0.18	0.13	1 082	7
176	0.1	2.75	3.2	6.7	64.9	0.19	0.14	1 193	7
198	0.1	2.85	3	6.6	64.4	0.18	0.15	1 296	7

Nutrition in Beef Cattle

Because they are ruminant animals, cattle have a digestive system that enables them to digest concentrates like barley grain or dry distillers’ grains as well as roughage like hay and grass thanks to the activity of a diverse microbial community in the rumen.

Cattle require sufficient quantities of energy, protein, water, vitamins, and minerals for proper nutrition. The needs will vary based on the animal’s class, age, health, and production stage. Feed, including both grazed and conserved feed, represents the largest expense in beef cattle operations.

Given that nutrition is frequently the most significant determinant of reproductive performance, managing feed resources to consistently achieve high reproductive rates at a reasonable cost will help ensure profitability for beef cattle operations. Profitability is significantly impacted by feed costs and feeds conversion efficiency in the backgrounding and feedlot sectors.

Quality of feed, cost, and effective digestion, absorption, and conversion are crucial for animal health, reproduction, performance, and profitability across all facets of the beef cattle industry.

A few key points:

Gradual diet changes (over 2 – 3 weeks) are necessary to allow the rumen microbial population to adjust to changes in the diet.
Young, actively growing forages and legume blends can often meet the nutritional requirements for normal growth and maintenance of cattle herds. Mature pastures, crop residues, or other low-quality forages may have reduced nutritive value, requiring supplementation of protein, energy or additional vitamins and minerals to maintain optimal health.
Energy is necessary for maintenance (feed digestion, core body functions, and activity requirements) and to support growth, lactation, and reproduction. It accounts for the largest proportion of feed costs and is the nutrient required by cattle in the largest amount.
Neutral detergent fibre (NDF) and acid detergent fibre (ADF) are indicators of the amount of fibre in a forage. Higher values indicate poorer digestibility and voluntary intake may be reduced.
Protein is required for maintenance, growth, lactation, and reproduction. It is a component of muscles, the nervous system and connective tissue.
Water is an essential nutrient for cattle, accounting for between 50% and 80% of an animal’s life weight. Insufficient water intake reduces animal performance faster and more dramatically than any other nutrient deficiency.
At least seventeen minerals are required by beef cattle and are divided into two groups, namely, macro-minerals and micro-minerals.
Most forage species have the highest quality at the vegetative stage, when leaves are lush and green, and stems are young and supple. At this stage, these forages may be able to supply most of the nutrition that the cattle require.
Knowledge of forage quality and animal requirements is necessary to formulate rations that will support and maintain a high plane of nutrition.
The nutritional requirements of beef cattle are influenced by the stage of production.

A. Nutrients

The study of nutrition in animals embraces ingestion, digestion and absorption of nutrients, their transport to the body cells and the removal of waste products of metabolism, including that part of the ingested food that is not absorbed. Although a thorough knowledge of all that is known of nutrition is useful to the practical farmer, only aspects essential to beef production will be discussed.

As mentioned already the nutrients in feeds are grouped as water, protein (which can also be a source of energy), energy sources, and minerals. This division is based on relatively simple laboratory techniques, and although modern technology makes it possible to determine the chemical composition in greater detail, this division satisfies most requirements for feeding farm animals.

Water.

Water is the most important nutrient. Without water animals die very quickly. Water shortages often result in reduced feed intakes, leading to poor animal performance. There is evidence that the provision of clean water in adequate quantities leads to improved animal growth. This is understandable because water is the fluid carrier of chemicals in the animal body. The water content of feeds varies from as much as 85% in some pastures to 10 – 15% in conserved, dried feeds. The water content of the feed is determined by weighing a representative sample of the feed, drying it in an oven to constant weight, and assuming that the difference in weight loss before and after drying is the moisture content of the feed. When comparing different feeds, the comparison is simplified when the composition is expressed on a dry matter basis.

Protein.

Protein can serve as a source of energy, but the main functions of proteins are their role as building blocks of the body, especially muscle, and many hormones and enzymes are proteins. Proteins are made up of amino acids, some of which are considered essential i.e., must be provided in a healthy diet because certain animals cannot synthesise the relevant amino acids. Because the rumen of ruminants contains many microorganisms which can produce essential amino acids, ruminants are not as dependent as mono-gastric animals on their diets for the provision of essential amino acids. As a rule, ruminants should ingest diets containing at least 10 – 15% crude protein. The crude protein content of feeds is determined by measuring the nitrogen content of the feed, assuming that all the nitrogen is contained in proteins, and multiplying the value by 6.25. This is based on the fact that proteins contain 16% nitrogen. For beef cattle, compiling rations using crude protein content as the measure of protein in the diet provides satisfactory results in most cases. Excess protein in a diet is not desirable. A crude protein content in a diet of 25 – 30% can be tolerated by cattle adapted to such diets, but higher levels of crude protein should be avoided.

Energy.

Energy comprises the bulk of most diets because energy provides the driving force to do work. The main sources of energy are starches and fats. With ruminants’ crude fibre, which comprises structural carbohydrates in plants, is utilised as an energy source. Although fats are a good source of energy, they usually do not comprise a significant proportion of energy in beef cattle diets. Should fats be included in rations for cattle, the fat should not exceed 5% of the total diet.

With cattle, when a diet contains less than 20% roughage, digestive disturbances are likely, although modern feed additives make it possible to feed rations to cattle containing as little as 15% roughage. The inclusion in a diet of excess amounts of carbohydrates (especially readily fermentable carbohydrates) e.g., maize meal, can cause acidosis. When carbohydrates are broken down in the rumen, acids are formed and when present in large amounts, the pH of the rumen drops to levels at which the rumen microflora cannot function effectively. The energy content of feeds can only be determined by more complicated laboratory procedures, including measuring the digestibility of the feed when fed to animals. The energy content of feeds is therefore usually not measured routinely. Previously the energy content of feeds was expressed as total digestible nutrients (TDN), but the present measure of the energy content is metabolisable energy (ME), which is measured in megajoules (MJ).

A megajoule is an energy or work unit equal to one million joules. The joule is the International System of Units’ energy unit (SI). ‘kinetics’ = movement

The digestibility of a feed is the proportion of feed not excreted in faeces and is assumed to have been absorbed into the animal’s body.

Minerals.

Minerals are divided into major- (required in larger amounts) and trace minerals (needed in only small amounts). Calcium, potassium, magnesium, sulphur, phosphorus, and chlorine are the essential major minerals, and iron, manganese, copper, cobalt, iodine, zinc, molybdenum, and selenium are the essential trace minerals. Fluorine, bromine, barium, and strontium could be essential. Chromium, nickel, tin, aluminium, vanadium, boron, lead, and titanium are usually present in feeds but are considered non-essential. The following Tables reflect the mineral requirements of cattle and the symptoms of mineral deficiencies.

Mineral requirements and maximum tolerable levels of minerals for beef cattle.

	Mean	Range	Maximum Tolerable Level
Calcium%	Refer to the Tables about Daily nutrient requirements for maintenance, growth and fattening of steers and of breeding stock in a beef herd.	0.18 – 0.53	2
Magnesium%	0.1	0.05 – 0.25	0.4
Phosphorus%	Refer to the Tables about Daily nutrient requirements for maintenance, growth and fattening of steers and of breeding stock in a beef herd.	0.18 – 0.37	1
Potassium%	0.65	0.5 – 0.7	3
Sodium%	0.08	0.06 – 0.10	10
Sulphur%	0.1	0.08 – 0.15	0.4
Cobalt mg/kg	0.1	0.07 – 0.11	5
Copper mg/kg	8	4 – 10	115
Iodine mg/kg	0.5	0.20 – 2	50
Iron mg/kg	50	50 – 100	1000
Manganese mg/kg	40	20 – 40	1000
Selenium mg/kg	0.1	0.05 – 0.30	2
Zinc mg/kg	30	20 – 40	500

Clinical symptoms of dietary deficiencies in livestock.

Decreased rate or cessation of growth

Rough coat, unthriftiness

Reduced appetite, anorexia

Decreased milk production

Emaciation, loss of mass

Dead or weak offspring

Stiff joints, lameness

Pica

Impaired reproduction

Collapse or death

Fragile, weak or fractured bones

Anaemia

Diarrhoea

Muscular incoordination

Decreased phosphorus in plasma

Staggering gate

Convulsive seizures

Straight pasterns

Craving of salt

Suppression of oestrus

Goitre

Day or night blindness

Decreased Vit A in plasma

Shy breeding

Watery eyes, nasal discharge

Secondary pneumonia

Decreased calcium in plasma

Arching back

Tetany

Oedema

Enlarged joints and bowed legs

Energy

Protein

Salt (NaCl)

Calcium

Phosphorus

Iron

Copper

Cobalt

Iodine

Vitamin A

Vitamin D

B. The Daily Nutrient Requirements of a Beef Herd

Data provided in the following nutrient requirement Tables can assist producers in determining specific beef cattle nutrient requirements. The values listed in the tables serve as a general guide for matching forage and feeding programs to cattle nutrient needs. Actual nutrient requirements vary depending on many animal and environmental factors. Monitor body condition and weight in mature cattle and growth rates of growing cattle to adjust cattle diets to achieve desired performance results.

Dry matter intake values are estimates based on published prediction equations. These predictions assume that adequate protein is supplied in the diet for maximum rumen fermentation. If the diet is deficient in protein, the dry matter intake values will overestimate actual cattle consumption.

Tabular values are intended for healthy, unstressed cattle in good body condition. Thin cattle need additional nutrients to improve their body condition. Cattle under stresses, such as weather extremes or physical exertion, also require extra energy for maintenance.

Daily nutrient requirements for maintenance, growth and fattening of steers.

Live mass	ADG (kg/day)	Energy requirements in MJ ME						CP (g)	DP (g)	Ca (g)	P (g)	Vit A ‘000 IU
		Energy concentration in MJ ME/kg DM of ration fed
		8	9	10	11	12	13
150	0.00	22	22	22	22	22	22	230	130	5	5	6
	0.25	29	29	28	27	27	27	460	270	13	11	10
	0.50	38	36	35	34	33	32	515	320	14	12	9
	0.75			43	41	40	38	560	365	19	15	9
	1.00				50	48	46	600	410	25	18	9
	1.25					58	56	640	455	31	21	9
200	0.00	27	27	27	27	27	27	300	170	6	6	8
	0.25	35	35	34	34	33	33	50	300	10	10	12
	0.50	44	42	41	39	38	37	555	345	14	13	12
	0.75		53	50	48	46	45	610	395	19	16	13
	1.00			61	58	55	53	655	445	23	18	13
	1.25				70	67	64	700	495	27	20	13
	1.50					81	77	750	545	31	22	13
250	0.00	31	31	31	31	31	31	350	200	8	8	9
	0.25	40	39	38	38	37	36	570	33	12	12	14
	0.50	51	49	47	45	44	43	715	430	18	16	14
	0.75		60	57	54	52	51	790	485	24	20	14
	1.00			69	65	63	60	855	540	30	23	14
	1.25				79	75	72	915	595	34	25	14
	1.50					91	87	915	595	34	25	14
350	0.00	40	40	40	40	40	40	455	260	10	10	12
	0.25	51	49	48	48	47	47	690	400	15	15	18
	0.50	63	60	58	56	55	54	745	440	17	16	18
	0.75	78	73	70	67	65	63	800	480	19	17	18
	1.00		89	84	80	77	74	855	525	22	19	18
	1.25			103	97	92	88	985	670	34	30	18
	1.50				117	110	105
	1.75					135	128
450	0	49	49	49	49	49	49	545	310	12	12	14
	0.25	61	60	59	58	57	56	765	445	16	16	20
	0.5	75	72	70	68	67	66	840	495	18	18	20
	0.75	91	87	83	80	78	76	900	540	19	19	20
	1		106	100	95	91	88	950	585	20	20	20
	1.25			120	114	108	104	1 000	630	24	23	20
	1.5				137	130	124	1 075	730	28	25	20
	1.75					158	150	1 075	730	28	25	20
500	0	54	54	54	54	54	54	810	470	17	17	17
	0.25	67	65	64	63	62	62	990	610	20	20	20
	0.5	82	79	76	74	73	72	1 030	650	22	22	23
	0.75	100	94	90	87	84	82	1 060	690	24	24	23
	1		114	108	103	99	95	1 105	750	26	26	23
	1.25			129	123	117	112
	1.5				147	140	133
	1.75					170	161

Daily nutrient requirements of breeding stock in a beef herd.

Pregnant Yearling Heifers – Last 3 – 4 Months of Pregnancy
Live mass	ADG (kg/day)	Min DM Consumption kg/day	Roughage %	ME (MJ)	CP (g)	DP (g)	Ca (g)	P (g)	VIT A ‘000 IU
325	0.4	6.6	100	53	580	340	15	15	19
	0.6	8.5	100	68	750	420	18	18	23
	0.8	9.4	85-100	84	850	500	22	20	26
350	0.4	6.9	100	55	610	350	15	15	19
	0.6	8.9	100	71	780	450	19	19	25
	0.8	10	85-100	88	880	510	22	21	28
375	0.4	7.2	100	57	630	360	15	15	20
	0.6	9.3	100	74	810	460	19	19	26
	0.8	11	85-100	92	960	550	22	22	31
400	0.4	7.5	100	59	650	380	16	16	21
	0.6	9.7	100	77	840	480	19	19	27
	0.8	11.6	85-100	96	1010	500	22	22	33
425	0.4	7.8	100	62	690	400	16	16	22
	0.6	10.1	100	80	880	500	19	19	28
	0.8	12.1	85-100	100	1050	600	22	22	34
Dry, Pregnant Mature Cows – Middle Third of Pregnancy
Live mass	ADG (kg/day)	Min DM Consumption kg/day	Roughage %	ME (MJ)	CP (g)	DP (g)	Ca (g)	P (g)	VIT A ‘000 IU
350		5.5	100	45	320	150	10	10	15
400		6.1	100	50	360	170	11	11	17
450		6.7	100	54	390	190	12	12	19
500		7.2	100	59	420	200	13	13	20
550		7.7	100	63	450	220	14	14	22
600		8.3	100	67	490	230	15	15	23
Cows Nursing Calves – Average Milking Ability – First 3 – 4 Months Postpartum
Live mass	ADG (kg/day)	Min DM Consumption kg/day	Roughage %	ME (MJ)	CP (g)	DP (g)	Ca (g)	P (g)	VIT A ‘000 IU
	350		8.2	100	67	750	440	24	24
	400		8.8	100	71	810	480	25	25
	450		9.3	100	76	860	500	26	26
	500		9.8	100	80	900	530	27	27
	550		10.5	100	85	970	570	28	28
	600		11	100	89	1 010	590	28	28
Cows Nursing Calves – Superior Milking Ability – First 3 – 4 Months Postpartum
Live mass	ADG (kg/day)	Min DM Consumption kg/day	Roughage %	ME (MJ)	CP (g)	DP (g)	Ca (g)	P (g)	VIT A ‘000 IU
	350		10.2	100	88	1 110	650	45	40
	400		10.8	100	92	1 170	690	45	41
	450		11.3	100	97	1 230	720	45	42
	500		11.8	100	102	1 290	760	46	43
	550		12.4	100	106	1 350	790	46	44
	600		12.9	100	110	1 410	830	46	44
Bulls – Growth and Maintenance – Moderate Activity
	300	1	8.8	70 – 75	85	900	550	27	23
	400	0.9	11	70 – 75	105	1 030	620	23	23
	500	0.7	12.2	80 – 85	113	1 070	620	22	22
	600	0.5	12	80 – 85	110	1 020	600	22	22
	700	0.3	12.9	90 – 100	116	1 080	600	23	23
	800	0	10.5	100	88	890	500	19	19
	900	0	11.4	100	96	990	550	21	21
	1 000	0	12.4	100	104	1 050	600	22	22

Minimum DM consumption is based on the general type of diet indicated in the roughage column. Approximately 0.4 kg of weight gain over the last third of pregnancy is accounted for by the products of conception.

Average milking ability = 5 kg per day

Superior milking ability = 10 kg per day

Roughage = good quality roughage containing at least 8 MJ ME/kg

C. Annual production Cycle of a Beef Cow

Annual production cycle of a beef cow.

Phase 1 – begins at calving. This is the period of greatest nutritional demand for the cow. She must lactate, repair her reproductive tract, resume heat cycles, and breed, and if she is a young cow, she must also continue growth and development. Her voluntary feed intake is highest at this point and as this blog explains, she requires a high-energy and protein diet of at least 62% TDN and 11% CP. If she is not fed to meet nutritional needs, she will lose weight and may not rebreed.

Phase 2 – begins with conception. The cow is now supporting herself, her calf (through lactation) and her foetus. Nutritional demands are still high as she reaches peak lactation but is lowered by 8 – 13% compared to the first phase. Cows that produce more milk will have higher nutrient requirements. The foetus is small, and its growth is slow, but cows and heifers often lose weight during this time.

Phase 3 – is when the cow is in mid-gestation. Immediately after calves are weaned, nutritional needs are at their lowest due to the end of lactation. Energy and protein requirements drop by up to 35% when compared to the peak demand. Foetal growth remains slow, and voluntary feed intake is the lowest during this period. This is the best time to put weight back on cows to help them gain condition. See the body condition information to learn more about how to ensure beef cattle are in ideal condition.

Phase 4 – is the final phase before calving, and cows must be in good body condition to give birth to a healthy calf, produce milk and re-breed quickly. Energy and protein need to increase by 20% compared to mid-gestation. During this period, the foetus can gain up to 27 kg and the placenta is growing as well. Nearly 75% of foetal growth occurs during this phase. Cows need to gain 0.5 – 0.68 kg per day, while weight gain for heifers should target twice that amount. The cow has reduced rumen capacity due to the growth of the calf, so a reduction in feed intake usually occurs in the latter portion of this phase.

Producers often modify their feeding strategies during the annual production cycle of the beef cow to align with her energy and protein needs as she moves through the cycle. For example, lower quality feeds such as straw reduce costs during Phase 3, when the cow’s nutritional requirements are at their lowest. In Phase 4, as the rumen has less room for feed due to the growing foetus, she will benefit from higher quality feed such as good quality alfalfa hay or some grain to provide extra energy. A common rule of thumb is 55-60-65% for total digestible nutrients (TDN) and 7-9-11% for crude protein (CP) for mid-gestation, late gestation, and lactation. More information on nutritional requirements can be found here.

D. Dry Matter Intake

While specific requirements for forage or feed intake do not exist, estimates of how much forage or feed animals will consume are needed for diet formulation and prediction of animal performance. This publication includes nutrient requirement tables that report dry matter intake and average daily gain values. Daily dry matter intake of forage and feed is the amount of forage and feed (excluding the moisture content) consumed in a day. Cattle require certain amounts of certain nutrients every day, such as protein, calcium, and vitamin A. To meet specific nutrient requirements, the percentage of nutrients in the diet for cattle is based on the quantities of forages and feeds consumed daily.

Many factors affect dry matter intake, including animal weight, condition, stage of production, milk production level, environmental conditions, forage quality, and the amount and type of forage or feed offered. Forages typically make up the majority of cattle diets on both cow-calf and stocker cattle operations. Forage intake capacity is affected by the stage of production and forage type and maturity.

Forage intake capacity of beef cows.

Forage Type and Maturity	Stage of Production	Forage Dry Matter Intake Capacity (% of body weight)
Low-quality forage (< 52% total digestible nutrients)	Non-lactating	1.8
Average quality forage (52 to 59% total digestible nutrients)	Non-lactating	2.2
	Lactating	2.5
High-quality forage (> 59% total digestible nutrients)	Non-lactating	2.5
High-quality forage (> 59% total digestible nutrients)	Lactating	2.7
Lush, growing pasture	Non-lactating	2.5
Lush, growing pasture	Lactating	2.7
Silage	Non-lactating	2.5
Intake estimates assume that protein requirements are met in the total diet. When protein requirements are not met, forage intake will be lower than the values in the table.

E. Factors Influencing the Nutrition of Cattle

Forage Availability:

Forage availability is the most important factor affecting forage intake on pasture. Insufficient available forage restricts intake. On high-quality pasture, intake is typically adequate when available forage dry matter is at least 50 – 750 kg per acre. Cattle harvest forages with their tongues, so very short forage can limit the amount of forage intake per bite (bite size). The animal has to walk farther and take more bites to consume an adequate level of forage. The extra walking allows less time for chewing and ruminating. When cattle are grazing short pasture, increased grazing time is often not enough to compensate for reduced bite size on forage intake.

The proportion of the leaf to the stem can greatly affect the bite-size, as cattle prefer leaves. Higher proportions of stem effectively reduce bite-size even if the total forage available is adequate. When the stocking rate is high, cattle on rotationally stocked pastures may be forced to consume more stem or low-quality forage, which can reduce intake. In contrast, cattle on a continuously grazed pasture can be more selective unless the pasture is overstocked and has low forage availability. Warm-season perennial grasses, such as bermudagrass, bahiagrass, and dallisgrass, with a higher proportion of stem may require the animal to harvest more but in smaller bites to obtain the desired amount of forage. Cattle avoid dead material if the green leaf is available, and bite-size may be restricted as the grazing animal seeks out green leaves.

Palatability:

Palatability refers to how acceptable a forage or feed is to an animal. Animals may spend time seeking out certain forage species and avoiding others, which affects bite size and effective forage availability. Cattle generally prefer grasses over clover and alfalfa. The tannins found in forages such as arrowleaf clover can reduce palatability. Nitrogen fertilisation will generally increase forage protein content and can increase forage palatability. Cattle prefer certain feed ingredients as well. For example, newly arrived stocker calves usually prefer dry feeds to wet feeds, such as silages. Cattle may even refuse extremely mouldy or otherwise unpalatable feeds. Palatability problems with hay or feed can increase feed waste.

Feeding Drive:

If adequate forage is available, an increased feeding drive usually increases forage intake. Body size, lactation level, growth rate, age, sex, and environmental factors all affect an animal’s demand for nutrients. Lactating beef cattle can consume 35 – 50% more dry matter than nonlactating cattle of the same size on the same diet. Cattle with greater milk-producing ability often also have increased feed intake needs. Body composition, particularly the amount of body fat, can impact feed intake. Dry matter intake decreases once cattle exceed a certain degree of the condition. Specifically, there is about a 2.7% decrease in dry matter intake for each 1 per cent increase in body fat past the range of 21.3 – 31.5% body fat. Diligent feed intake monitoring can help determine when cattle have reached appropriate finish conditions.

Physical Satiety:

Physical satiety is the degree of “fullness” or distention of the digestive tract or abdomen caused by the volume of digesta in the tract. It is affected by forage quality, which determines how rapidly forage moves through the digestive tract. For example, intake of low-quality bermudagrass will typically be lower than on annual ryegrass or white clover because bermudagrass remains in the rumen much longer. The beef animal’s digestive tract breaks down annual ryegrass and white clover quickly, absorbs the nutrients, and rapidly passes the small amount of residue through the digestive tract. Forage intake can be limited by the capacity of the digestive tract because receptors in the rumen wall are sensitive to stretch. Yet factors other than gut capacity may influence the rate of digestion and intake.

Intake by beef cattle fed high-concentrate, grain-based diets are likely controlled by metabolic factors, not bulk fill. Feedlot cattle may increase their dry matter intake in response to a change in the level of bulky roughage (by as little as 5 per cent or less of dry matter) or a shift to a more fibrous roughage. per centage of dietary neutral detergent fibre, (NDF) supplied by roughage appears to be useful for predicting the effects of roughage quantity and source on dry matter intake. In general, as NDF levels increase, dry matter intake decreases.

Toxic Factors:

There is considerable evidence that cattle can learn to avoid toxic or imbalanced feeds and to choose between two feeds of different nutritional value to avoid nutrient excesses or deficiencies. For example, cattle will graze a shorter time without changing bite size on toxic endophyte-infected tall fescue than on endophyte-free or nontoxic endophyte-infected tall fescue. Selenium, cyanide (from prussic acid), or an alkaloid (for example, from toxic endophyte-infected tall fescue) can severely reduce intake.

Nutrient Deficiencies:

Intake can be depressed whenever a feed is deficient in essential nutrients, particularly protein. Nitrogen deficiency is common in cattle consuming low-nitrogen, high-fibre forage. Correcting this deficiency with supplemental nitrogen (protein) can increase dry matter intake substantially. Supplementing with protein helps increase intake when forage crude protein levels fall below 6 to 8 per cent. Low protein levels are most commonly seen in poor-quality forage with inadequate nitrogen fertilisation. Supplementing with grain-based concentrate feeds tends to decrease forage intake, and forage intake drops more with high-quality forages than with low-quality forages.

Feed Physical Form:

The physical form of feeds and forages can impact feed intake. With forage, fine grinding can improve intake, possibly by allowing it to pass through the digestive tract more rapidly. However, fine grinding of concentrate feeds can decrease feed intake.

Ionophore Use:

Monensin is an ionophore used in beef cattle diets that helps improve cattle growth and efficiency. Beef cattle may drop dry matter intake by approximately 4 – 6% when fed monensin at recommended levels. Monensin can be added to receiving rations at levels required for coccidiosis control without affecting the feed intake of lightweight calves. Monensin can reduce feed intake variation among individuals in group-fed cattle. Other ionophores, such as lasalocid, have limited effects on feed intake.

Implant Use:

Growth-promoting implants tend to increase feed intake by 4 – 16%. The actual increase in feed intake may depend upon the animal’s stage of growth at the time the implant is administered. Dry matter intake predictions should be decreased by about 8 per cent for non-implanted cattle.

Environment:

Extreme temperatures and weather can impact feed intake. The thermal neutral zone is the effective temperature range within which performance rate and efficiency are maximised. As temperatures rise above the animal’s thermal neutral zone upper critical temperature, the point at which heat stress begins, dry matter intake falls. As temperatures drop below the animal’s thermal neutral zone lower critical temperature, the point at which cold stress begins, dry matter intake increases. Temperature-based stress on cattle impacts energetic efficiency.

Effects of temperature on beef cattle maintenance, gain, and intake; TNZ = Thermal Neutral Zone.

The effects of temperature on feed intake depend upon the animal’s thermal susceptibility, acclimation to the conditions, and diet. Mud, precipitation, humidity, and wind heighten temperature effects on feed intake. The duration of these adverse conditions and the photoperiod, or length of daylight, may also influence feed intake. The breed also strongly influences how environmental conditions affect feed intake. The adaptability of cattle to the environment can impact feed intake and cattle productivity.

Dry matter intake adjustment factors for specific environmental conditions.

Environmental Condition	Dry Matter Intake Adjustment Factor¹
Temperature, degrees Celsius
> 35 °C with no night cooling	0.65
> 35 °C with night cooling	0.90
25 – 35 °C	0.90
15 – 25 °C	1
5 – 15 °C	1.03
-5 – 5 °C	1.05
-15 – -5 °C	1.07
< -15	1.16
Mud, centimetres
None	1
Mild, 9.9 – 20.1 cm	0.85
Severe, 29.9 – 59.9	0.70
¹Multiply this factor by predicted dry matter intake to determine adjusted dry matter intake for the specific environmental condition.

Management:

Management can impact feed intake levels in beef cattle. Commingled newly weaned calves tend to consume more dry matter in the first weeks after weaning. Management practices such as programmed feeding, multiple feed deliveries per day, and consistent timing of feed delivery help regulate feeding behaviour and reduce variations in feed intake by penned cattle. However, the effectiveness of these practices is typically evaluated by the pen and does not usually account for individual variation.

Individual Animal Variation:

There is considerable individual animal variation in feed intake beyond what would be predicted based on size and growth rate. This difference in intake is called net or residual feed intake (RFI). Genetic variation in the RFI of beef cattle exists both during growth and in adult cattle. Residual feed intake is moderately heritable, indicating that genetic improvement can be made through selection. From a cost-production standpoint, a lower RFI value is more desirable. An animal with a negative RFI is more efficient because it consumes less feed than expected, while a positive-RFI animal is less efficient because it consumes more feed than expected.