Continuous grazing of a herd in one pasture.
Animals are placed in a camp when the forage is first ready to graze at the start of the growing season and they or their replacements are left in that camp for the entire grazeable period of each year. The number of animals may be varied, but at least some grazing animals are present in the camp at all times during the grazeable period of the vegetation. Livestock may, however, be removed for dipping, weighing and similar short-term operations.
Continuous grazing does not necessarily imply the use of only a limited number of camps, but this is often the case where it is applied.
The simplest form of continuous grazing is where the whole farm is one camp and the animals in one herd remain on the farm each year – the farm being stocked at its grazing capacity. Veld deterioration and soil erosion resulting from area and species selective grazing are inevitable. Veld deterioration can be reduced by adjusting the stocking rate to suit the areas preferred by stock, but this is difficult to achieve in practice. No resting is possible.
The more sophisticated form of continuous grazing is where there are many camps, which have been delineated based on uniform or homogeneous units. Each camp is stocked at the grazing capacity for that camp. Thus, area selective grazing and the development of footpaths are reduced (each camp has its water point). However, species selection is not eliminated, it is not possible to apply rests to favour certain species and rotation is difficult. Some form of rotation is possible by moving some animals from one camp to another.
Advantages of continuous grazing:
- Cheap in terms of physical inputs. Few camps are necessary, usually as many camps as herds or flocks, and hence the capital investment per hectare, in terms of fencing and the provision of watering points, is low;
- Management is simple and little labour is required to move stock.
- Easy to keep grazing records.
- Good individual animal performance can be expected if the stocking rate is low: animals can select freely.
- Little disturbance to animals (animals are not moved around, except for dosing and dipping) provides for better animal performance.
Disadvantages of continuous grazing:
- The grazing is inefficiently utilised, especially where much of the grazeable material consists of ‘semi-palatable’ species, and production per hectare is usually low, although production per animal may be satisfactory. Booysen (1975) suggests that the optimum economic stocking rate for a continuously grazed pasture is lower than that for the same pasture rotationally grazed.
- There is a lack of flexibility in terms of rationing feed during slow growth periods or drought. No provision for resting for the accumulation of material to be used as fodder reserve for times of slow growth during the growing season or droughts.
- Selective grazing takes place. (i) as a result of the low stocking density the more palatable plants are over-utilised. Fewer desirable plants then have the opportunity to grow to physiological maturity, set seed and propagate. (ii) Patch or area selection also occurs and these areas are continuously grazed so that detrimental effects on the cover and botanical composition must occur. Trampling of ‘sweet patches’ or palatable patches is unavoidable and bare patches often occur.
- The condition of the vegetation declines as a result of selective grazing. This is largely manifest in the disappearance of the palatable plants (overgrazing reducing their vigour and competitive ability) and the replacement of the palatable plants with less palatable undesirable plants (eg. souring of the veld, bush encroachment, karoo encroachment, mshiki and weed encroachment in pastures).
- Replacement of desirable species by undesirable plants results in a reduction of the grazing capacity (the desirable species usually contribute the most in terms of animal production). Because of the general harmful effects of selective grazing, veld deterioration sets in. The vegetation is damaged, becomes more sparse, bare areas develop and the grazing capacity declines further.
- As a result of the sparse cover and the development of bare areas, runoff is increased. This leads to increased water and wind erosion (loss of basic resource – soil) and less efficient utilisation of the rainfall (reduced penetration = less moisture available for growth).
- Trampling and overgrazing around watering points, especially if badly positioned or far apart, may become severe and thus promote soil erosion. In addition, the formation of footpaths is promoted. This often leads to donga erosion.
- With continuous grazing, there is no provision for providing rest during critical growth periods or for specific purposes. Diversified rest periods (vigour, seeding, seedling establishment, replenishment of reserves) are necessary for sustained maximum production and the maintenance of the desired plant density and species composition in certain veld types and pasture mixtures.
- Seasonal fluctuations in plant growth are not catered for.
- Periodic removal of excess herbage, especially with planted pastures, is not possible.
- Continuous grazing requires an accurate assessment of the correct grazing capacity and the choice of the correct stocking rate.
- Fertilising, especially with high levels of nitrogen, can lead to high nitrate and nitrogen levels in the herbage, following the application of nitrogen, which can affect animal health and performance.