|Environmental Handbook Volume II: Agriculture, Mining/Energy, Trade/Industry (GTZ, 1995, 736 p.)|
|30. Livestock farming|
2.1 Types of husbandry
2.1.1 Pasture use in general
The most noticeable consequence of grazing is the defoliation of plants by the animals, which influences the structure of the pasture vegetation and the variety of species which it contains. The precise nature of this influence depends on the type of animal concerned, the stocking rate (grazing pressure) and possibly also the time of year. Cattle and sheep tend to eat grass, whereas camels and goats prefer leaves.
An ideal sheep or cattle pasture will thus consist primarily of grass and herbaceous plants, while an ideal camel or goat pasture will contain more trees and bushes.
Grazing can stimulate plant growth and encourage the growth of creeping ecotypes of a particular plant species rather than those which grow upright. In grass/legume pastures, grazing often favours the legume component, because animals generally prefer grass during the early part of the vegetation period; with competition reduced in this way, legume growth is promoted. However, the young stages of some legumes are also popular with animals. While light grazing and browsing on bushes and trees can stimulate growth, removal of vegetation by livestock on a larger scale can reduce growth or even cause plants to die off and may hinder regeneration of fodder bushes from seeds and suckers.
The effects resulting from trampling of the vegetation by livestock depend primarily on the type of animal concerned, the stocking rate, the soil condition and the topography. Damage caused by trampling can increase soil erosion; however, the roughening-up of the ground can also create better conditions for germination and thereby promote plant regeneration. Where the soil in humid regions is heavily waterlogged, the vegetation cover can be destroyed as a result of trampling.
The seeds of many pasture plants are very small and can pass through the animals' digestive tract without any impairment of their germination capacity. Certain plants are thus dispersed with the animals' dung. Hard-shelled seeds are also scarified and the seeds are redistributed and sown by the animals.
Only a small proportion of the nutrients and energy intake by livestock actually finds its way into the animal products used by man. The remainder is excreted via dung, urine and, in the case of ruminants, methane (a gas which plays a part in the greenhouse effect). The breakdown of organic matter in the digestive tract of ruminants gives rise to energy and nutrient losses similar to those resulting from microbial breakdown in the soil; as the breakdown process in the stomach of ruminants is considerably faster, however, the grazing animals accelerate the nutrient cycle. If the animals are penned overnight, the excretion of dung in the pen means that the pasture is deprived of nutrients. Although the dung collected in pens can be used in arable farming and horticulture or for production of biogas and can thereby contribute to improving soil fertility, the loss of nutrients can accelerate degradation of the pasture vegetation.
In semi-arid and arid regions, the considerable fluctuations in annual rainfall mean that vegetation growth varies greatly not only according to the time of year but also from one year to another. The herbaceous vegetation layer in particular will thus not exhibit consistent growth. In drought years there may be so little vegetation growth that all the herbage is eaten by the animals. If shrubs and trees are not to suffer permanent damage, the amount of their vegetation consumed as fodder must not exceed a specific proportion of the annual growth, otherwise their capacity for survival and regeneration will be jeopardised.
Permanent damage is generally considered to have occurred when the vegetation's capacity for regeneration has been impaired and the surface of the ground has suffered erosion by wind or water. In view of the differences between plant communities and the differing regeneration capacities of the various species, it is not possible to lay down any universally valid standards specifying how much land can be used without impairing the productivity of the vegetation and what stocking densities are possible. American estimates work on the basis that 50% of the vegetation can be used, while studies from West Africa take figures of 30-50% (le Houerou 1980). Others graduate permissible vegetation use according to rainfall and take different levels of permissible utilisation for the bush/tree layer (25-50%) and the grass/herbaceous layer (30-50%) (Schwartz 1989). Factors which can assist in assessing degradation include the age structure and species composition of the tree and shrub community, seed reserves in the soil for the herbaceous plants and possibly also soil cover as well as depth and condition of the A-horizon.
The distribution of animals in an arid pasture area is determined primarily by the availability of water. Deep wells containing plenty of water supply a large number of animals and may thus give rise to serious overgrazing in their immediate vicinity. The size of the area around a well that can be used by animals for grazing depends among other things on the dry-matter content of the fodder, the type of animal and the animals' physiological status. Inadequately protected wells and watering places can easily be contaminated by dung and may also constitute a health risk for the local population if drinking water becomes contaminated. The concentration of animals around wells can promote the spread of epizootic diseases. Around every watering place there is a certain area which, although it contains an accumulation of nutrients by virtue of the dung produced by numerous animals, is almost totally devoid of vegetation as a result of trampling. The size of this area depends on the design of the watering place (e.g. troughs on hard ground) and the way in which access to it is controlled (e.g. fencing-in of watering places). Use of fertiliser in arable farming and horticulture in the vicinity of the watering place will not give rise to any problems.
Pastureland comprises natural pastures, fallow land and harvested fields. Forested areas, which in some cases are under the control of forest administrations, can also be used as pastures. In many cases, for instance in North Africa, the major proportion of the forest yield is derived from livestock farming. Fodder production is an integral part of agroforestry. It must be pointed out, however, that forest pastures are often over-used. If this is to be prevented, a wide variety of measures are necessary: reduction of tensions between forest administration and local farmers; employment of an adequate number of appropriately motivated personnel in order to enforce the regulations limiting pasture use; provision of alternative fodder resources for local livestock owners; steps to prevent use of pastures by non-local livestock owners not engaged in agriculture; reasonable charges (where payment is made for use of forest pastures) by comparison with the price of other fodder resources; and involvement of the local population in pasture-use planning. Both the dry and humid tropics offer examples of balanced pasture management which takes forest growth dynamics into account.
2.1.2 Pasture use with supplementary feeding
The environmental impacts of supplementary feeding depend on the context and the type of feed. Where fodder is of poor quality but available in large quantities, supplementary feeding of minerals can improve utilisation of the "standing hay". Provision of supplementary feed in the form of feed concentrate or high-quality roughage soon leads to a reduction in the amount of fodder consumed per animal during grazing, which benefits the pastureland. If, however, the number of animals is increased on account of the improved fodder supply and the natural pasture continues to be used, there is a greater risk of degradation. In some cases (e.g. in North Africa) livestock are given so much supplementary feed that this feed covers not only their performance requirement but also part of their maintenance requirement. Another reason for overgrazing is the desire to improve the quality of the animals' meat, since this will be reflected in higher meat prices. Meat quality is influenced in particular by the fact that the animals move around more and by the improved basic fodder supply.
2.1.3 Fodder production
Erosion-control strips can be used for fodder production. Appropriate planting of permanent fodder crops (such as sulla in North Africa) can serve as a form of "soft" erosion control. Fodder growing within a crop rotation system can have positive effects on soil structure and soil fertility (see Plant Production). The possibility that fodder crops may compete for land with crops that can be used as food for human beings must be borne in mind.
In the case of certain fodder crops, a large quantity of nutrients is taken from the soil together with the green matter. If these nutrients are not replaced, or if the dung is not returned to the field, there is a danger that the nutrient balance may be disturbed. If mineral fertilisers and herbicides are used in fodder production, there is a risk that surface water and groundwater may become contaminated and that the diversity of species may be reduced at the same time.
While pasture use primarily involves ruminants, chickens, pigs and small livestock such as rabbits and guinea pigs are generally kept in confinement.
The environmental impacts of keeping livestock in confinement depend on the number of animals, the type of animal, the nature and origin of the feed and whether the livestock housing is open or closed. The environment prevailing in the animal-sheds (temperature, humidity, light, presence of noxious gases, dust and germs) has an effect on the animals, while livestock housing itself has an effect on its immediate environment through odours, liquid manure and noise. Where ruminants are kept, methane (a gas which plays a part in the greenhouse effect) is also released.
If livestock are kept in confinement, the vegetation suffers far less damage than if the animals are allowed to graze. However, use of cut fodder means that the soil is deprived of nutrients on a considerable scale; if these nutrients are not replaced, there is a danger that soil fertility may be reduced.
The enormous quantities of liquid manure produced where a large number of animals are kept can impair drinking-water quality and contaminate both surface water and groundwater. Large-scale chicken farms located near cities give rise to particularly adverse environmental impacts on account of their need to dispose of dead birds and droppings. Liquid and solid manure represent a major potential source of infection - especially for children - in many developing countries, particularly if no measures are taken to prevent contact with them. When used as fertilisers, liquid and solid manure can have a beneficial effect on soil fertility and soil structure, provided that they are not applied in excess.
2.2 Farming systems
Ranches permit uniform management of comparatively large areas. Large-scale farms of this type nevertheless do not guarantee conservationist use of pasture resources (Harrington et al. 1984). In dry years a ranch too requires alternative fodder resources or the number of animals must be reduced in good time, otherwise heavy losses are likely. Supplementary feeding can lead to over-use of pastureland and thus increases the risk of erosion. When a large farm with "rational" stocking rates or a pasture reserve with a controlled stocking rate is established in an area where traditional livestock husbandry predominates, it should be borne in mind that although the reduced stocking rate on the land concerned may be more appropriate to site conditions than the original rate, the exclusion of animals from this land will increase the grazing pressure in the surrounding area.
Particularly in humid regions, large-scale land clearance to create pastures for ranches substantially reduces the diversity of species found in the vegetation. Apart from the resulting erosion problems, there may also be a risk of climatic changes over a wide area. The fact that ranches generally keep only cattle gives rise to one-sided utilisation of resources, which either permits only very low stocking rates or calls for sizeable inputs to preserve the pastureland. There is also a danger that the pastureland may be acidified as a result of waterlogging. Damage caused by trampling can have an adverse effect on the soil structure, leading to increased surface-water run-off and a greater risk of erosion.
Although ranches can improve the urban population's food supply, their carrying capacity per unit of area is smaller than that of traditional farming systems (e.g. Cruz de Cavalho 1974, de Ridder & Wagenaar 1986).
Environmental protection measures are difficult to realise where ranching is concerned. Attempts to standardise the carrying capacity of pastures are the subject of considerable dispute on account of the complex interrelationships and numerous variables involved, particularly in assessment of vegetation (e.g. Sandford 1983).
Some systems, such as those found in Australia, are based on detailed long-term studies and official determination of the permissible maximum stocking rate. As the land in Australia is generally not in private ownership, but is instead leased out by the government on a long-term basis, specific conditions can be imposed and the lease revoked if need be. In many countries the necessary data are not available and monitoring institutions are either non-existent or not equipped to perform the essential tasks. Rules aimed at preventing erosion should be worked out together with the ranch managers concerned.
2.2.2 Pastoral systems
In such systems, animal husbandry is the sole or principal economic occupation. Herding and a high degree of mobility make it possible to utilise resources in a manner complementing arable farming or to utilise areas that can be used for grazing only at certain times of year.
Pastoralists often keep mixed species herds, which permits intensive use of a wide variety of fodder resources. The products derived from the herds include milk, meat, traction power and manure.
· Integration of grazing and arable farming
Where pasture resources are used in combination with arable farming, the amount of land available for grazing varies greatly in the course of the year. During the growing season only natural pasture and fallow land can be used for grazing, while during the dry season harvested fields are also available for this purpose. Grazing has a variety of effects on fallow land and natural pasture. The species composition of the vegetation may change in such a way that a larger proportion of the vegetation can be used as fodder or for other purposes; at the same time, however, intensive grazing can also lead to degradation. If herded animals are penned at night, nutrients accumulate in the night paddock as a result of the droppings and urine produced by the livestock. These nutrients can be used to preserve soil fertility on arable land (dung), but are thereby removed from the nutrient cycle on the land used for grazing. Leaching from the night paddock can lead to contamination of surface water and groundwater. Use of crop residues as fodder may accelerate the nutrient cycle and result in redistribution of nutrients in a particular field or among fields. If crop residues are used on a large scale the soil cover may be reduced and this can lead to erosion. Rights to use fodder resources must be established through agreements between pastoralists and arable farmers.
A high degree of flexibility and mobility is required on the part of the pastoralists in order to permit ecologically appropriate and economically sound use of arid regions. Mobility in turn calls for large herds. In the course of their migration the pastoralists and their families must for the most part live on the products which they can derive from their herds. Reduced mobility generally leads to overgrazing, accompanied by increased soil erosion, in the area around the newly created settlements and to under-use of other areas. Under-use can also give rise to changes in the balance of species and reduce the vegetation's productivity.
As herds and people become increasingly sedentary and concentrated in specific areas, use of green twigs and branches to construct livestock paddocks and as domestic fuel leads to destruction of the woody vegetation.
· Grazing rights
Land and pasture use rights may comprise seasonal rights of use in specific areas and grazing rights in areas located a long way from one another. Apart from creating an opportunity to use land resources for grazing as well as for arable farming, this also helps to balance risks, as rainfall in arid regions is often highly localised. Communal grazing rights predominate in such areas. Communal pastures are traditionally used by clearly definable groups of livestock owners. Depending on the
group's structure and effectiveness, this makes it possible to stipulate stocking rates and times at which the pasture is not to be used. In regions such as East Africa, controlling access to water is an important means of controlling stocking rates. Open access pastures - frequently equated with common pasture - offer virtually no opportunity for such a step. In such a context, creation of watering places outside the traditional structures can encourage opportunistic use and thus contribute to overgrazing. The secondary consequences of such a development will be degradation of the vegetation, reduction of the soil's rainwater infiltration rate and increased soil erosion.
· Changes in ownership
Changes in the herd ownership structure can likewise adversely affect the pastoralists' resource management. When herdsmen look after cattle owned by other people, for example, they are often allowed only to use the milk. In order to have a secure livelihood they require large herds of their own if they are not to become impoverished. Moreover, the owners' desire to keep a check on their property may cause them to restrict the herdsmen's mobility and thus also their flexibility where pasture management is concerned. This too can result in over-use of the vegetation (disturbance of the balance of species within the flora, disturbance of the water balance, soil erosion).
· Division of labour
In pastoral systems, the men are generally responsible for management and marketing of the largestock, while the women frequently tend the small ruminants and have responsibility for milk processing and marketing. The women's role is often underestimated, as it is the men who represent the family vis-is other people. The decentralised processing and marketing of milk ensures a relatively reliable milk supply in rural areas, even though a woman may process and market only a few kilograms of milk a day. When milk is processed at household level, consideration must be given to possible hygiene risks (e.g. danger of infection).
· External influences
Pastoral land use frequently necessitates agreements between various population groups. External influences - and that includes government programmes - may disturb the often fragile equilibrium. If, for example, arable farming is expanded onto land used by pastoralists for dry-season grazing or as reserve pasture, the loss of this pastureland can increase the pressure on other areas and lead to overgrazing. Should the arable farmers start to keep livestock on a larger scale, the pastoralists
may find themselves driven out into marginal areas. This not only has consequences in terms of grazing management and livestock productivity but can also affect the welfare of the population groups concerned.
If their mobility is restricted, pastoralists may be forced to make intensive long-term use of marginal areas on a scale which exceeds the natural carrying capacity.
The resultant degradation process intensifies competition for the decreasing fodder resources. By promoting over-use of the available land it also reduces the number of species found locally and marginalises large sections of the pastoral population.
2.2.3 Smallholder livestock husbandry
The number of livestock owned by a smallholder can range from a few small animals (e.g. chickens) to large herds, e.g. twenty goats or ten head of cattle. Livestock management normally takes second place to the interests of arable farming. Many smallholders keep more than one type of animal.
Smallholders generally use pastures with supplementary feeding (at least on a seasonal basis) or keep their livestock in confinement. Large herds - such as village herds - may be mobile (cattle placed in the charge of a herdsman by their owners).
The animals may be allowed to graze freely, or may be herded, tethered or kept in fenced pastures. The practice of fencing off pastures with wooden posts - which may have to be replaced at frequent intervals on account of termite damage - can have adverse effects on the species composition and density of the tree stand. By contrast, use of "living fences" or hedges to subdivide pastureland has positive effects on the tree stand but requires a considerable amount of labour.
Clearing land to create improved pastures can increase the erosion risk and thus have an adverse influence on soil fertility. Creation of improved pastures, particularly with legumes, can be integrated into ley farming (seeded pasture rotation) and will improve soil structure and fertility. Competition for use of fodder resources may arise between livestock owners, above all between pastoralists and smallholders as well as between the smallholders themselves, and can thus impose increased pressure on the available land.
As in pastoral systems, management of largestock is frequently the men's responsibility, while the women are in charge of the smallstock. As women in many rural societies have no land ownership rights, livestock husbandry plays an extremely important part in enabling them to accumulate capital. The income earned from animal husbandry can be used to finance necessary expenditure for arable farming (fertiliser, seed, hired labour, creation of erosion-control strips), while the animals' dung can be used to preserve soil fertility. Livestock perform a particularly important function as a form of "risk reduction" in regions where arable yields tend to be unreliable. If the harvest is insufficient to meet the family's subsistence requirements, animals can be sold to permit the purchase of staple foods. Without this means of offsetting risks it would be necessary to extend the area under cultivation, which would have negative effects in terms of soil erosion, soil structure, nutrient balance and diversity of species.
A changeover from pasture use to keeping livestock in confinement can have beneficial effects on the diversity of plant species and assist in preventing erosion. The increased concentration of liquid manure and dung may lead to greater pollution of surface water and groundwater. Keeping livestock in confinement requires more labour than pasture use and it is generally women who are called upon to perform the extra work.
High-performance animals have more demanding requirements in terms of fodder supplies and veterinary care. If chemoprophylaxis is necessary, pathogen strains resistant to the chemotherapeutic agents used can develop (see environmental brief Veterinary Services). Introduction of high-performance animals frequently does not lead to a reduced number of livestock; it does not lessen the burden on the available fodder resources either.
The actual and potential advantages of indigenous breeds and species are often underestimated. With a one-sided promotion of the use and importation of high performance animals, there is a danger of losing genetic resources adapted to the natural environmental conditions.
Urban livestock husbandry can be regarded as a special category of smallholder livestock husbandry. As urban livestock owners purchase far more fodder than those in rural areas, their existence can encourage fodder growing in the vicinity of towns. This can have positive effects on soil structure and fertility, besides boosting the fodder growers' income. Dairy cattle are kept in urban areas to supply the urban population with fresh milk. While other animals are kept primarily to meet their owners' food requirements, they can also serve as a form of "savings bank" and as a means to accumulate capital. The dung produced by the animals can help to improve the soil structure and nutrient balance, but may well give rise to direct and indirect health risks if it is used or disposed of incorrectly. As in rural areas, women make an important contribution to urban livestock husbandry, although it can be assumed that the division of labour between the sexes is less strict than in rural society.
Smallholder animal husbandry also includes beekeeping. Apart from producing honey, bees can substantially increase fruit yields by pollinating the blossoms and help to preserve the diversity of species within the flora. Modern intensive beekeeping involves chemical control of pests (mites etc.); such measures can create health risks for humans if the chemical agents are incorrectly used and if residues find their way into the honey. Importing of higher-performance strains of bee can eradicate indigenous species. Production of honey and beeswax, which is predominantly a male domain, can be a highly profitable source of income in rural areas.
Environmental protection measures in the field of pastoral and smallholder livestock husbandry may involve steps to change framework conditions or direct intervention. Examples of measures aimed at changing framework conditions include discontinuation of subsidies for feed grains - in North Africa such subsidies contributed to widespread overgrazing - and changes in land law (land reform). Where direct intervention in pastoral and smallholder production systems is envisaged, it is essential that the groups affected be involved in the measures right from the planning stage. The measures planned may relate to a wide variety of different areas, e.g. water resources management, erosion control, fodder growing or - where smallholders are involved - promotion of confinement. Simply demanding a reduction in the number of animals - as was frequently done in the past - reflects an inadequate understanding of the way in which pastoral and smallholder production systems function.
2.2.4 Large enterprises with intensive animal production (commercial farming)
Large-unit animal production generally does not depend on the availability of land to provide forage, as fodder is imported from other parts of the country or from abroad. For the purpose of supplying the urban population, large-scale livestock production focuses on pigs and poultry.
Large farms consume far more fossil energy per product unit than traditional farms. If growth stimulants such as antibiotics or hormones are added to the fodder, there is a danger that residues may be found in foods of animal origin and that resistant pathogens may develop.
The high water consumption of large farms is also likely to lead to excessive utilisation of scarce water resources.
In confinement housing, the prevailing in-house-micro-climate (temperature, humidity, noxious gases such as ammonia, hydrogen sulphide and methane, dust and germ content of the air) can have adverse effects both on the animals and on the farm workers (health risks). The mere size of the farms means that the danger of surface water and groundwater being contaminated by liquid manure and farm effluent is far greater than in the case of smallholdings. The problems attached to the disposal of dung and animal carcasses are also likely to be greater, as is the related hygiene risk. Use of disinfectants can endanger water, soil and possibly also health.
Where cattle are involved, sizeable quantities of methane - a gas which plays a part in the greenhouse effect - are produced in the animals' stomachs and released.
If large farm enterprises are in competition with smallholdings, they can have an adverse effect on the smallholders' income. This may force smallholders operating under marginal conditions to engage in arable farming instead of livestock husbandry. Apart from giving rise to undesirable consequences with regard to the balance of species and soil fertility, such a step also increases the danger of erosion in the region concerned. Some large farms, such as commercial cattle-feed lots or large dairy farms (agricultural combinates), may also compete directly with smallholdings for agricultural land (e.g. in irrigated areas) and thereby force the smallholders into marginal areas. However, this risk is greater in the case of plantations and other crop-growing farms than in the case of livestock farms.
Environmental protection measures on large farms with intensive livestock management focus primarily on technical aspects: housing design, whole farm layout, ventilation, distance from settlements, precautions during storage and disposal of liquid manure and dung, hygiene measures such as disinfection, ban on use of growth stimulants, fencing-in of livestock housing etc. Technical standards in Central Europe are well documented (e.g. the German DIN standard 18910 on controlled environment in livestock housing, specifications laid down by the Association of German Engineers [VDI], maximum workplace concentration values (MAK), construction specifications issued by the German committee on technology and construction in agriculture [KTBL]).