by Geoff N. Hinch and Justin J. Lynch
DEPARTMENT OF ANIMAL SCIENCE, UNIVERSITY OF NEW ENGLAND, ARMIDALE NSW 2350, AUSTRALIA
Sheep and goats are biologically adapted to a complex species-specific environment (Figure 1). This is reflected in social, physical and nutritional needs which have to be addressed in the laboratory setting in order to foster the animals' well-being and hence ensure the validity of research data collected from them.
Like most other ruminants, sheep and goats are social animals who need the presence of other conspecifics in order to experience a state of well-being. This is particularly true in the research setting where stressful experimental manipulations are best counterbalanced by the presence of a familiar companion. Sheep and goats should therefore be housed in a social setting whenever possible (Figure 2). Research protocols requiring individual housing must be scrutinized carefully to ensure that the time period of social deprivation is limited to the very minimum. Behavioral changes such as augmentation of aggression (usually subtle in female animals but very obvious in males), increased/decreased activity (for example during isolation from other group members), incomplete/abnormal reproductive behaviors, decreased foraging, decreased grooming/stretching, stereotypies, teeth grinding, increased vocalization (particularly in goats), increased respiration rate, unusual posturing, reduced alertness, apathy, and anorexia are reliable indicators of impaired well-being (Hinch 1993). Figure 3 gives some guidance to identify well-being problems. Sheep seem to be rather stoical, while goats are much more demonstrative, allowing easy recognition of impaired well-being.
Sheep and goats are conspicuously vigilant and their natural response to fear-inducing situations is to instantaneously congregate (flock) and flee. Sheep have a strong need to flock and this species-typical behavior requires at least three animals (Lynch et al. 1992). Hence the saying that "One sheep is not a sheep". Goats are less gregarious but still show a pronounced flocking response.
Free ranging animals always maintain uninterrupted visual contact with at least one other member of the flock. This safeguards the coherence of the flock and its acute alertness and quick reactivity to fear-provoking stimuli. Indoor housed animals should therefore always be positioned in such a way that they can see at least one other conspecific.
Visual isolation is extremely stressful for sheep and goats, and under no circumstance should they be housed by themselves. An individual animal should never be exposed to a potentially stressful situation, such as venipuncture and drug application, without the presence of a familiar conspecific.
Sheep and goats establish social dominance hierarchies which are based on differences in age, sex and possibly body-weight and horn-size. These rank-determining factors must be taken into consideration when new groups are formed in order to avoid aggressive conflicts. It is preferable to establish groups of animals who are already familiar with one another and are of the same age and sex.
Adult males tend to exhibit intense, agonistic behaviors if they are grouped with each other or placed in situations of territorial or sexual competition. It is therefore good advice to house mature rams and bucks in separate pens.
In the wild, juvenile males ( less than 2 years old) form compatible male-only groups. Hence, they can be housed without undue risk in groups of up to 20 animals. However, excessive and possibly injurious socio-sexual mounting may become a serious problem in such groups, unless they are monitored very carefully on a daily basis.
Figure 3: The major behavioral changes associated with threats to well-being
Like most other gregarious animals, sheep and goats not only establish a rank order that is based on dominance-subordination but also one that is based on leadership, with particular subjects leading, and the rest of the group following from one location to another, e.g., from a grazing area to a water hole. In the context of confinement, individual animals can readily be trained to lead others during routine handling procedures such as weighing and veterinary examination. The preferable means for movement is to allow the animals, as a group, to move away from the handler to the target location. The use of fear stimuli such as dogs and noise is not recommended in confined areas where the animal cannot escape. Taking advantage of such voluntary movement minimizes stress responses during handling, thereby enhancing the reliability of research data collected.
Goats and sheep are relatively fearful by nature. Any changes in their surroundings make them apprehensive. Even a change of the diet results in the animals being reluctant to eat the unfamiliar foodstuff (Lynch et al. 1992). The human shape elicits a specially strong fear response which can only be modulated with patient conditioning.
The inherent neophobia of sheep and goats makes it an imperative that animals subjected to experimentation be carefully habituated to all new, i.e. fear-inducing situations. The adjustment to the stress associated with new food, to new housing arrangements, to new experimental conditions, and to new personnel is best buffered by working with an animal in the presence of one, or preferably several familiar, well-experienced conspecifics (Pearson and Mellor 1976).
Temperature and Humidity
Small ruminants are well adapted to extreme temperatures, with their fleece/coats providing an insulative layer which protects them from cold and heat. The comfort zone for sheep and goats is wide, ranging from 0-30°C (32-85°F). Exceptions are the neonate and the newly shorn animal who are susceptible to cold, especially if they are wet or if they have not fed. Sheep are particularly sensitive during the first 7-10 days after shearing.
If animals are recovering from surgery, it is advisable to keep the ambient temperature slightly higher than normal as physiological thermoregulation is inadequate during the first 24 hours following anaesthesia. Under such conditions a temperature of 20-28°C (68-82°F) is recommended. The neonatal lamb and kid are also most comfortable within this temperature range (Alexander 1974).
Sheep and goats rely on evaporative cooling from the respiratory tract. Consequently, high humidity associated with high temperatures is stressful to the animals as it interferes with their ability to regulate body temperature. If indoor temperatures rise above 30°C (85°F), a comfortable environment can be maintained by keeping the relative air humidity below 60%.
Ventilation is normally of little consequence to sheep and goats. However, newborn lambs and kids become extremely susceptible to hypothermia when air movement exceeds 1m/s (3ft./s; Alexander 1974). Indoor housing necessitates some air movement to ensure that toxic gases formed during metabolic processes and decomposition of urine and feces are removed.
If the manure is removed regularly, ventilation rates of 0.5-1.5m3/hour/kg liveweight are recommended to reduce the likelihood of respiratory diseases (Wathes et al. 1983).
Ventilation systems should be designed in such a way that drafts at animal level are avoided while adequate air movement above animal level is guaranteed.
Lighting Sheep and goats are relatively fearful when experiencing sharp contrasts in lighting. This has practical implications in the context of handling because the animals are reluctant to move from bright to dark (e.g., shade) areas. A uniform lighting pattern (minimum of 4 Watts/m2) is therefore recommended (Liklatter et al. 1983).
Sheep and goats are seasonal breeders, with decreasing daylight initiating the onset of the reproductive cycle. Exposure to the natural light rhythm is therefore important for indoor-housed animals who are assigned to breeding programs.
Flooring The choice of bedding and flooring is dependent on the age and physiological state of the animals. A 0.15 m (6 in.) layer of straw or coarse (to prevent "balling") sawdust mixed with wood shavings are recommended as comfortable, species-appropriate bedding. Wooden slatted floors or metal mesh floors are also well accepted by the animals. The gap between the slats should be 14-16 mm (0.6 in.) to allow easy passage of fecal material and guarantee safe footing for the animals. The grid of the mesh should be 20 mm (0.8 in.) to provide adequate support for the animals' feet. The area below the floor has to be accessible for easy cleaning or should be equipped with an automatic flushing system.
Space Pens of individually housed adult sheep/goats (weighing up to 35 kg [77 lb.]) should be no less than 2 m (6.6 ft.) long and 1 m (3.3 ft.) wide to make certain that the animal has enough room to comfortably turn around and to make a few steps in one direction.
In the group-housing situation, the minimum floor area per animal should be 2m2 (21.5 sq.ft.) to allow for social spacing and hence to minimize agonistic conflicts resulting from spacial restriction.
All enclosures must be high enough (0.9 m [3 ft.] for adult sheep, 1.2 m [4 ft.] for adult goats) to prevent animals from jumping over them.
Environmental Enrichment Wild sheep and goats live in heterogeneous mountain and valley grassland environments (Figure 1). This suggests that the animals are very responsive to variation in their environment. Field studies conducted in sheep (Stolba et al. 1990) show that ewes and wethers respond to the addition of trees, logs and earthen mounds by increasing their repertoire of behaviors compared to those seen in barren paddocks. The animals are responsive to such environmental enrichment presumably because it reduces boredom resulting from understimulation.
Sheepand probably also goatskept in deep litter pens readily accept "toys," such as plastic drums and suspended balls to counteract boredom. Such enrichment objects may also have a therapeutic value if the animals are afflicted by behavioral pathologies such as wool biting/chewing and bar chewing.
Nutritional Needs It is well known that sheep are neophobic to new foods (Lynch et al. 1992) and although they will sample a number of available feeds, they will normally eat the most familiar one. Consequently sheep, and to a lesser degree also goats when exposed to new food will eat very little until they overcome their fear and recognize the food as acceptable. If the food has flavors that were previously associated with negative consequences, the animal will be averse (Provenza 1992) and may even starve rather than eat.
Goats and sheep have an intrinsic need to ruminate and to chew the cud. The overall fibre content of the ingested food should be about 40% to satisfy this need. A lack of fibre may lead to the development of behavioral disorders such as bar chewing and wool biting/chewing. Sheep and goats tend to develop digestive problems due to acidosis when their diet is high in readily fermentable carbohydrates such as wheat or barley. They require at least a period of 10-14 days to safely adjust to a high energy cereal/grain diet.
Mineral imbalances are common problems when the animals are completely dependent on an artificial diet. They are highly susceptible to copper poisoning, which can readily be avoided when molybdenum (2mg/kg) is added to the diet. Rams and bucks often develop urinary calculi (small stones). Feed formulations with extra sodium chloride (3-4%) are the best prevention against this problem because the salt ensures that the animals drink sufficient quantities of water.
Feed troughs should not have any sharp edges and corners. They have to be shallow enough so that the animals can maintain visual contact with each other. Trough space per adult animal should be 0.30 m (1 ft.) to allow all animals of the flock to forage at the same time. This situation circumvents agonistic disputes arising from competition over access to feeding space. Drinking water must be clean, fresh and free of copper. It should be provided in self-filling bowls which are cleaned regularly.
The major issues to be considered when housing sheep and goats for experimental purposes are:
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