Sample and Evaluate Animal Feeds

Quality control of incoming ingredients is crucial to predicting the quality of a complete feed, supplement, premix, and so on. An important first step is accurate sampling and a complete examination of the ingredient before unloading. Sampling and inspection procedures need to be in writing and kept in a Quality Control Procedures Manual.

The goal in sampling any lot of ingredients or finished feed is to obtain samples that are representative of the lot in question. A wrong answer which may arise from incorrect sampling, incorrect handling of samples, analytical error, and so on, is worse than no answer. Thus, it is our responsibility to know the proper procedures and techniques for sampling to be sure that correct formulations can be made.

Food or feed is any substance, originating from plants, animals, or any other source, consumed by any organism to provide nutritional support. When consumed and assimilated, food is used in the body to maintain and repair body tissues, promote health and growth, sustain life, and provide energy, for reproduction and other vital body processes through the release of its nutrients. Essentially, the basic nutritive components of food are carbohydrates, proteins, fats, minerals, vitamins, and water, which are absorbed in the body in various usable forms.

Food given to food-producing animals, whether made up of single or multiple materials, is generally referred to as feed or feedstuff, and could be fed as raw, semi-processed or processed. Feeds may be live organisms, particularly in the production of aquatic organisms. Animal feeds are either classified as:

• Fodder – could be classified as roughages (freshly cut forage, hay or dry forage, straw, root crops, stover and silage) and concentrate such as grains, legumes and by-products of processing.
• Forage – plant materials consumed by grazing animals either directly as pasture, crop residue, and immature cereal crops. However, forage materials cut as fodder, particularly fresh, hay, and silage are sometimes loosely referred to as forage.
• Mixed feeds – produced from several feed ingredients combined in different proportions to achieve a particular nutritional quality. Feed ingredients, including additives, may or may not add any nutritional value to the mixed feed and comprise components originating from plants,

 

Sampling Feed for Analysis

1. Baled hay.

Use a commercial forage sampler (for example, the Penn State sampler) to core subsamples from 15 – 20 bales from each lot of hay you want to be tested, then mix core samples for a single composite sample representing that particular lot. For the hay and other feeds sampled, using a 19-litre bucket helps hold and mix subsamples of a given lot. Each core subsample should penetrate the bale at least 30 cm.

The bales should be selected at random for each lot of hay. If the hay will be fed by its cutting (first-cutting alfalfa, and so on), each cutting should be analysed as a separate lot. If a mixture of cuttings or classes of hay will be fed, a proportional number of bales can be used from each class to approximate the feed offered to the animals.

For square bales, sample from the end and use the full length of the sampler tube. Place each core in the container. For round bales, sample across the bale at the centre, not the end.

 
Forage sampling a round bale using a Penn State sampler with an electric drill (left) and a hand crank (right).
 

You can sample baled hay without a forage sampler by removing a small section from each bale (15 – 20 bales) and cutting the hay into 8 cm lengths with shears or a hatchet. This is a less desirable technique because you’re almost sure to lose leaves. On Lucerne, this is not advised because you would need a good distribution of leaves and stems in your sample. Make every effort to include a representative combination of leaves and stems because they have very different nutrient profiles. Placing samples on a smoother surface can be helpful to ensure leaves are collected.

2. Pasture.

Pasture sampling is the most difficult. Fertility and moisture differences in a single pasture add to the problem.

Sample by picking 8 – 10 locations at random. Clip the forage at a 25 cm stubble height using a square foot (30 x 30 cm) frame or 1.92-foot squared hoop Mix all the collected forage and take a representative sample for analysis.

Accurately calculating the range and forage production of grazing resources is important when estimating carrying capacity and stocking rate. The most accurate method to calculate forage production is the clip-and-weigh method. This method requires the harvesting of standing forage at a given time to predict available forage. The available forage is measured by hand clipping and weighing a specified number of plots within a grazing or forage production area.

These plot weights are averaged to account for variability in production across the field or pasture to be grazed. The average plot weights then are multiplied by a conversion factor to determine the approximate pounds per acre of production.

This production parameter only provides a measurement of plant production and not necessarily forage production because some of the weight may be weedy species that livestock may not consume. To avoid overestimating the stocking rate, clip only the plants found within your frame that the scheduled class of livestock will consume.

The following supplies are required for your Range and Forage Production Sampling Kit:

• Range hoop or frame.
• Clippers.
• Scale to measure weight in grams.
• Paper or plastic bag to place clipped forage in for weighing.
• Markers to label bags.
• Paper or forms to record data.

A second sampling method is to observe cattle, determine which forages are being grazed and then sample specific plants accordingly. This is a preferred method in unimproved pastures where selective grazing is evident. However, determining accurately how much of which forage to sample can be difficult. With a little practice, an experienced manager can identify accurately the species being consumed at the time of sampling.

Green pasture samples should be dried or frozen immediately to prevent marked chemical changes. The most practical alternative is to pack the sample tightly in a plastic bag, exclude all possible air and then put it in a freezer. Once frozen, ship it to a laboratory in a container with good insulation.

Also, be sure to contact the lab and arrange for the package to arrive on a day when the sample will be processed immediately (avoid late-week shipping that results in thawing and fermenting during the weekend). Following these procedures will allow the sample to arrive in a cool condition or with a minimum of a silage-like fermentation.

When choosing to dry a sample, take care to control the temperature and time the sample is exposed to heat. Drying for too long or at too high a temperature will alter the composition of your sample significantly. The microwave can be an excellent tool for drying samples.

 
Sampling pasture (Image credit: Erin Gaugler, NDSU).
 

3. Silage.

All silage samples should represent several locations in the silo to ensure a representation of the silage and should be collected after fermentation is complete. The representative sample must be packed tightly in a plastic bag, with all air excluded, and sealed. The sample should be sent to the laboratory as soon as possible, or frozen and then shipped in an appropriate container.

If the silo is open and you are feeding from it actively, the face of the silage should be cleaned off in the centre. Remove a column of silage 15 cm by 30 cm from top to bottom, mix it thoroughly and then take a representative sample.

If the silo is not opened, dig a series of four to 6 holes from the top with a post-hole digger or suitable equipment. Spoiled silage should be placed beside the hole to be returned after sampling. Mix the samples of good silage from each hole and take a representative sample. Be sure holes are packed tightly with the silage that has been removed to avoid undue spoilage.

4. Sacked feed.

Most sacked feed is mixed thoroughly. However, we recommend that you sample at least 5 – 6 sacks (500 g – 1 kg), mix the samples and submit a representative sample (500 g) for analysis. Either a small probe or sack thief should be used when available. Be aware that settling is quite common, even in sacked feed, making thorough sampling and remixing before feeding important.

5. Bulk concentrates.

Commodity feeds should be analysed as a composite of at least 10 – 15 areas of a given lot of feed. When mixing the composite, avoid segregation by particle size or the true sample value may be distorted.

At least 500 g, or a quart, of material, should be sent to the laboratory. Be advised that these results represent bulk averages and will not give you information on the uniformity of nutrient content in the mix.

If you’re experiencing inconsistent herd performance using these feeds, the uniformity of the mix may be questionable, so you should employ a different technique. Taking several samples of the commodity and having each analysed will allow the producer or feed nutritionist to do a better job of adjusting the ration to accommodate the feed differences.

6. Grain in a bin.

Using a grain probe to obtain the sample is highly desirable. However, if one is not available, you can grab samples randomly from 10 – 15 areas of the bin, mix them and send a representative sample (1 quart) for analysis.

 
Manual slotted grain probe.
 

7. Coproduct feeds.

Coproduct or byproduct feeds have become increasingly popular. A sampling of these feeds is very important because large plant-to-plant variations can occur in nutrient contents, and in some cases, even large load-to-load variations can occur within given processing plants. Collect grab samples from four to five locations from each load received, composite them and submit them for analysis.

The moisture content of high-moisture coproduct feeds also can be highly variable, so analysis for dry matter and adjusting as-fed feeding rates accordingly is very important. Specific minerals in coproduct feeds (especially sulphur in distillers’ coproducts) can cause health issues in cattle, and mineral testing may not be part of standard analysis packages.

Be sure to consult with the laboratory to ensure you are requesting all analyses that you need to make appropriate feeding decisions.

 

Sample Handling

Proper handling of the sample between the farm and laboratory ensures the best results. The general rules are:

• Sample size: minimum of 1 quart (be sure the sample is representative). All forages should be chopped to a length of 3 inches or less to make handling easier.
• Pack tightly to exclude air (i.e., seal airtight). Use plastic bags in all cases except for very dry samples.
• Freeze samples or send samples to the laboratory as quickly as possible. Indicate the analysis wanted by letter or with the appropriate form if part of an organised program.
• All letters, instructions, checks or money orders should be put in a first-class mail envelope and attached to the mailing container with the samples. The sample container can go as fourth-class mail.
• Address the letter and sample container with the correct laboratory address and return address.

Feed sampling checklist. 
 

Interpreting Feed Analysis

We need to analyse feeds to know what we are feeding. Feed analysis allows you to know what your feed is deficient in or adequate in to allow you to meet the nutrient requirements which allow the animal to perform (grow, lactate, run, and so on). Often this is through combining different feeds that meet the animal’s specific needs. These needs have been determined through many years of research and are published in nutrient requirement tables.

Book values are averages for various feeds. give you an idea of what the feed contains regarding nutrients. In no way should book values replace actual feed analysis values because feeds vary, especially forages.

What do the feed analysis results mean?

• Dry matter (DM) – the percentage of feed that is not water. Most nutrient requirements are on a DM basis.
• Crude protein (CP) – includes true protein and nonprotein nitrogen. It is a calculated value of % N X 6.25.
• Available CP – considers the CP that is bound and unavailable to the animal.
• Neutral detergent fibre (NDF) – the hemicellulose, cellulose, and lignin content of a feed. The higher the value, the more structural carbohydrate and typically the less digestible.
• Acid detergent fibre (ADF) – cellulose and lignin. The higher the value, the lower the digestibility and the lower energy available to the animal.
• Ash – minerals are present in the feed. Value tells nothing about the kind of minerals present in the feed.
• Ether extract (EE) – this is a measure of fat present in a feed.
• Relative feed value (RFV) – a measure of the overall nutrient value of the forage.

RFV = (% Digestible DM x % DMI) / 1.29

Digestible DM = 88.9 – (% ADF x 0.779)

% DMI = 120 / NDF %

Average grass hay containing 53% NDF and 41% ADF will provide for an RFV < 100. Above 100 is high-quality forage, and < 100 is poor-quality forage.

Food is deemed to be unsafe if it hurts human health or it would make the food derived from food-producing animals unsafe for human consumption. Animal feed plays a critical role in the production of safe and nutritious food. Several considerations enhance quality and effective decision-making in the feed and food production chain(s). Feed sampling and analyses are essential parts of the processes to ensure that feedstuffs and the resultant food animals meet all necessary standards. The reliability and quality of the analysis depend on the accuracy of sampling. Therefore, adequate care must be taken to ensure that the analytes are handled in a way that will prevent degradation and errors. Where a feed which has been identified as not satisfying the feed safety requirement is part of a batch, lot or consignment of feed of the same class or description, it shall be presumed that all of the feed in that batch, lot or consignment is so affected, unless following a detailed assessment there is no evidence that the rest of the batch, lot or consignment fails to satisfy the feed safety requirement. This is an important point if you get an adverse sample result when sampling.

 

Legislation – Fertiliser, Farm Feeds, Agricultural Remedies and Stock Remedies Act No. 36 of 1947

The South African Policy of Animal Feeds is a national policy with a multi-sectorial approach that provides the framework for the regulation and legislation of animal feeds in South Africa. Policy objectives:

• To provide for an effective and efficient regulatory system that will ensure that the manufacture, distribution and use of all feed ingredients and animal feed result in safe feed and food products.
• To ensure that the programs and procedures available for the regulation of animal feeds and that regulatory oversight of the animal feed manufacturing industry, is effective, and efficient, and that such program is implemented in a coordinated and holistic manner.
• To provide tools to manage challenges facing this and related industries and avoid unnecessary control measures to make the industry globally competitive.
• To promote active participation in the animal feed industry by offering incentives to the industry and bridging the gap between the first and second economies.

Consideration of recent developments in agriculture and other Acts which are indirectly involved with the regulation of animal feeds is not included, except the Medicine and Related Substance Control Act No. 101 of 1965.

Some of the Acts not considered in the current legislation include:

• Agricultural Product Standards Act No. 11 9 of 1990 determines the standards and requirements regarding control of the export of feed products.
• Meat Safety Act No. 40 of 2000 governs the use of safe animal products to be used for human and animal consumption.
• Animal Health Act No. 7 of 2002 provides measures to promote animal health and control diseases and regulate the importation and exportation of animals and things. The act will replace the Animal Disease Act No. 35 of 1984, which currently provides the legislative framework once the President has proclaimed the Animal Health Act.
• Agricultural Pests Act No. 36 of 1983.
• National Environmental Management Act No. 107 of 1998 provides for cooperative environmental governance by establishing principles for decision-making on matters affecting the environment.
• Genetically Modified Organisms Act No. 15 of 1997 provides measures for managing activities involving GMOs.
• The National Environmental: Biodiversity Act No. 10 of 2004 provides for the management and conservation of South Africa’s biodiversity within the framework of the National Environmental Management Act, 1998; the protection of species and ecosystems that warrant national protection; the sustainable use of indigenous biological resources; the fair and equitable sharing of benefits from bioprospecting involving indigenous biological resources.
• National Environmental Management Act: Air Quality Act No. 39 of 2004 provides for the regulation of air quality to protect the environment by providing reasonable measures for the prevention of pollution and ecological degradation and for securing ecologically sustainable development while promoting justifiable economic and social development.
• National Water Act No. 36 of 1998 provides for the fundamental reform of the law relating to water resources; to repeal laws; and provide for matters connected therewith.
• Occupational Health and Safety Act No. 85 of 1993 provides for the health and safety of persons at work.

 

Organisation and Administration

The Department of Agriculture will be the primary authority that will regulate the licensing of feed manufacturers and registration of additives. An officer of the state will be appointed to administer the Feeds Act. This will include looking at the resources required by Government to effectively implement the new Act.

 
Livestock feeding.