agricultural production guidelines
m
Veld in KwaZulu-Natal
Co-ordinated Extension KwaZulu-Natal Veld 9.2 1999
GRAZING SYSTEMS
N M Tainton
Professor Emeritus, University of Natal
P C V du Toit
KwaZulu-Natal Department of Agriculture
Continuous
Grazing
Rotational Grazing
Grazing Philosophies
Multi-Camp Systems
INTRODUCTION
Grazing systems range from continuous grazing systems, where only one camp is allocated to each group of animals, through to rotational grazing systems, where more than one camp is allocated to each group of animals. There are many advantages which can be attached to each of these systems, and it is not the intention here to attempt to identify the most suitable system for any particular situation. This will vary according to circumstance, and, in particular, to different veld types and conditions, to different livestock systems, and to different levels of management expertise. Each of a number of systems may therefore have its place, depending on the conditions. The two approaches to grazing systems are best described by listing the various advantages and disadvantages of each.
Advantages
- Management input is less than that in rotational systems. Animals enter a camp at the start of the season and remain in that camp for the entire season.
- Infrastructural costs are kept to a minimum, since only one watering point need be provided and no internal fencing is necessary.
- Animals do not need to be disturbed at regular intervals.
- Grazing records are easily maintained.
- Animals individually perform well in the short term, because they can select a high- quality diet from the entire grazing area.
Disadvantages
- Stocking rate needs to be precisely adjusted, and there may be a need to either add or remove animals during the season.
- It is necessary to stock at lighter rates than would be possible under a rotational system, in order to prevent the over-utilisation of preferred species and preferred areas within the camp.
- It is not easy to adjust for seasonal fluctuations in growth rate, since forage cannot be rationed through the season. It would not be possible, for example, to close areas to grazing in order to conserve forage for later grazing.
- Grazing is normally extremely selective, so that the efficiency of utilisation of the available forage is often very poor. Some areas are heavily grazed (and thus lose vigour), while others are ignored (and thus become moribund).
- Since animals do not need to be moved regularly, there is a temptation to neglect them.
- Supervision of licks and watering points is more easily neglected than under rotational grazing.
- Veld condition usually deteriorates through the invasion of pioneer and unpalatable plants (Increaser II species in selected areas, and Increaser I species in non-selected areas), so that animal performance declines in the long term.
Advantages
- Areas with different grazing potential, or of varying palatability, can be fenced off separately, and treated according to their individual needs.
- More efficient utilisation of fodder can be achieved by concentrating animals for an appropriate length of time in each camp. Where selective grazing is inevitable, this can be largely confined to only some of the camps, which can then be burned to simulate uniform utilization.
- Herbage of the desired quality can be provided to the animals by adjusting the length of the regrowth period between successive grazing periods.
Veld can be rationed to animals, to make provision for periods of slow growth, or droughts.
Excess herbage can be conserved as hay or as foggage, which can be fed to animals at a later stage with licks.
The intensity of grazing can be controlled more readily than in continuous grazing, by manipulating the stocking density and the period of occupation.
Graziers are encouraged to inspect animals more frequently (during movement of stock).
Since lick troughs normally follow the animals from camp to camp, these are more likely to be regularly inspected than where grazing is continuous.
Since animals are in each camp intermittently, the natural cycles of parasites are likely to be broken.
Veld retains its condition, provided the appropriate rotational system is applied efficiently.
Disadvantages
Infrastructural costs are higher (fencing and the provision of water).
Increased management time and expertise are required.
Increased labour inputs are required.
Animals are disturbed regularly.
Animals do not normally perform as well in the short term as under continuous grazing, because they have less opportunity to select.
A number of different grazing philosophies can be applied to rotational grazing systems, depending on the objectives of the grazing system. These are described below.
Controlled selective grazing (CSG) is also known as high production grazing (HPG). The aim of this philosophy is to promote good individual animal performance, while maintaining the vigour of the palatable species. Here animals are moved from a camp as soon as they have grazed the palatable plants to a moderate level (so that no more than 40 to 50% of their leaf is removed). Animals are not forced to graze the unpalatable plants.Controlled selective grazing
Non-selective grazing
Non-selective grazing (NSG) or high utilisation grazing (HUG) is aimed at maximum utilisation of all forage in a camp. High stocking density is normally required to achieve this. Animals are forced to graze all species (palatable as well as unpalatable).Short duration grazing
Short duration grazing (SDG) requires that animals remain within a camp for only short periods. The main objective here is to remove the animals from a camp to prevent plants from being defoliated more than once during the same period of occupation. This allows plants to recover sufficiently before being regrazed. Both CSG and NSG can be applied according to the principles of SDG.Within all of these systems, specific rests should be given to allow plants to complete certain necessary functions, such as seeding (where this is required), reserve accumulation, and so on. Such rests should be integrated into the grazing system. Refer to Production Guideline 9.3 in this series for more information on resting.
(Note that various options for cattle and/or sheep production systems for sourveld are discussed in more detail in Production Guideline 9.8 of this series.)
A multi-camp system is a form of rotational grazing which should meet the needs of both the veld plants and the animals. An example is described below.
The area to be grazed is divided into four main blocks, and, where possible, homogeneous vegetation units are separated. One of these blocks should be rested each season in rotation, so that each has one rest in four years. This block may be used for winter grazing. Three blocks (75% of the system) are grazed in rotation during the growing season. Each of the four main blocks should be divided into a number of camps. Initial divisions should be based on differences in the vegetation within each block. Thereafter divisions should be made to facilitate management.
This basic, four block system would operate in sour and mixed veld as follows.
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One block would be rested for the entire grazing season.
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This block could be grazed during the winter (with licks if necessary), and any residual material burnt at the end of winter. The camps of this block then enter the grazing cycle in the next season as the priority camps.
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The following season, camps of the priority block are grazed as soon as the palatable species have reached a height of about 150 mm. The camps in the block which is due for resting may be used as buffer camps for the early spring period before they enter their summer rest. This would allow the grasses in the priority camps to accumulate sufficient leaf material following the burn.
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The period of occupation of any camp should be as short as is practically possible and preferably not longer than about two weeks. The preferred length will, however, depend on growing conditions at any time. The better the growing conditions, the shorter should be the period of occupation.
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The period of absence should be long enough to allow the palatable plants to recover sufficiently in order to maintain their vigour. Bear in mind that grasses normally grow much faster in the early season than in the late season, so that periods of occupation and absence should, ideally, both be shorter in the early season than in the late season.
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The priority block (the one which has recently been burned) is grazed whenever the desirable grasses are ready to be grazed, irrespective of the condition of the other camps.
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When the camps of the priority block have been adequately grazed, the animals should be moved to the camps of the block burned one year previously, and then to those of the remaining block, provided that the priority block is not ready for grazing.
In a normal wet season, the application of this system will lead to the following situation.
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The camps of the priority block will be relatively uniformly grazed, with little accumulation of unacceptable residual material.
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The camps of the second block will be reasonably patchily grazed.
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The camp of the third block (which is destined to be rested in the following season) will normally be very patchily grazed.
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The camps in the fourth block will be rested for the growing season and are available for grazing during winter. In a dry season, however, it is likely that all camps will be fairly uniformly utilized.
Each block moves one along in the cycle in the following season, with the full cycle being completed in four years. One of the main objectives of such a system is that selective grazing is concentrated in the block that is due for a rest in the following season. Camps of the block which has recently been burnt are grazed non-selectively in an attempt to prevent the accumulation of unpalatable residual material for as long as possible. Inevitably, however, selection will take place, but this will increase the longer the camp remains unburned and the closer the camp comes to its next rest and burn year.
In sweetveld, selective grazing is not normally a serious problem. Here there is not normally a wide range in the palatability of the different grasses, and animals can usually be persuaded to graze all species reasonably well. In these situations, it is the yield of forage, and not its quality or palatability, which has the greatest effect on animal production. The objective of management must therefore be to stimulate yield through promoting plant vigour. This is done by grazing only leniently and providing sufficient periods of recovery after grazing. The fact that the grasses retain their palatability, even during long periods of absence, means that periods of absence can be long without materially affecting animal performance. Also, there is a need here to develop a reserve forage bank to
cover the relatively frequent dry periods that are a characteristic of sweetveld environments. To cater for this, as much as one third of the veld should be in a season-long rest at any time. Here the provision of long periods of absence in the grazing rotation will also help to even out the seasonal forage flow.
When planning a grazing system, certain other general factors should be considered:
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Cattle may be grazed alone, but sheep should always be accompanied by cattle in a ratio of at least 1 AU of cattle to every AU of sheep (approximately 5 - 6 sheep).
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This combination should ideally graze in a camp together, but, if this is not possible, cattle should follow sheep.
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Where unpalatable residual material accumulates, grazing pressure on the grazed plants is intensified. Such residual material should, therefore, be removed whenever it becomes excessive.
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The main restriction to animal performance in sourveld and mixed veld areas is forage quality, whereas in sweetveld areas it is forage quantity. Management in sourveld and mixed veld areas should therefore be designed to ensure that the animals are offered material of acceptable quality. This is controlled in the short term by the maturity of the material offered to the animals, and in the long term by the species composition of the grassland sward. In sweetveld, on the other hand, the main objective should be to promote plant vigour and high yields. This is done by ensuring that grazing is never too heavy, that adequate rests are provided, and that palatable perennial grasses are encouraged. While many of the pioneer annual grass species of these areas are highly palatable, their productivity is usually very low.
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The higher the stocking rate, the poorer will each animal perform, irrespective of the grazing system used. This is because the ability of the animals to select a high-quality diet will be progressively reduced as stocking rate increases.
It is clear that the grazier is faced with a number of alternatives when choosing a grazing system. The merits and disadvantages of each system and philosophy should therefore be assessed in conjunction with the prevailing conditions on the farm. These conditions include biotic (e.g. veld composition and condition, the types of animals used in the system) and abiotic (e.g. climate, soils, topography) conditions, as well as economic conditions (i.e. whether money is available to develop the infrastructure necessary for a rotational grazing system).