Considerable research work has been carried out with sheep, mainly mutton breeds, but less attention has been given to dairy sheep and particularly goats as milk or meat producers although milk yield and milk composition of goats have been reported (Sands & McDowell, 1978; Devendra & Burns, 1970; Parkash & Jenness, 1968 & Jenness, 1980).
It is difficult to describe the feeding and management of the sheep and goat industry around the world because of the many interacting factors such as production system, management system within each production system, genetic potential of the breeds, biological constraints etc. The systems of sheep and goat production can be divided into the following categories:
Finewool production from sheep and goats as the main products and meat as a byproduct.
Meat production from sheep and goats as the main product and wool, fibre and skin as byproducts.
Dual purpose sheep and goats with the main emphasis on milk or meat production or milk and meat given equal importance.
Within the meat and dual production systems the following four management systems can be identified:
Extensive (migratory, free range, pasture or range grazing).
Semi-intensive (pasture or range grazing, use of supplementary feeding mainly on crop residues and conserved roughage).
Intensive (grazing on improved pastures, zero grazing, conserved forage, crop residues and increased use of concentrates).
Tethering (small size flocks of 2–10 animals). This is a subsistence family system and the animals live on kitchen remnants crop residues, grazing near inhabited areas and other supplementary feed).
In the migratory system sheep and goat farmers make use of the seasonal pastures located in different areas. In the mountanious regions of Asia, Europe and North America climatic conditions limit growth of vegetation in winter and so flocks are moved to lowlands; in summer flocks are moved to highlands where feed is available. In the semi-arid and arid regions land use is seasonal and movement of the animals is dictated by rainfall and availibility of grazing.
Agricultural Res. Institute,
In the semi-intensive systems usually there is integration of animal and crop production. Moving from the extensive to the intensive systems of production the performance of animals is improved and higher inputs used with the objective of obtaining a high output of product (Orskov, 1982).
THE NUTRITION OF SHEEP AND GOATS
It is extremely difficult to present data collected from allover the world on the nutrient requirements of sheep and particularly of goats. For this reason as a general guide the recommended minimum requirements of sheep (NRC, 1975) and goats (NRC,1981) are suggested. The energy requirements of sheep and goats are similar according to NRC (1981). For dry non-pregnant animals the maintenance requirements are 0.42 MJME/kg0.75.
During the first 15 weeks of pregnancy energy requirements increase by 15%, providing also for a slight weight gain, and during the last stages of pregnancy they increase by 80–100% compared with dry animals. For each kg of sheep milk (6% fat) and goat milk (4% ) 7.5MJME and 5.2MJME are required, respectively. The requirements for digestible crude protein range from 2.3 – 2.8g /kg 0.75 for sheep and goats for maintenance, increasing during the last stages of pregnancy by 80–100%. For each kg of goat milk or sheep milk 45–70 g or 60–90 g digestible crude protein are required, respectively.
Studies on the foraging behaviour and the dietary habits of sheep and goats (type and parts of plants they eat, their tolerance to saline or bitter feed and saline water, the distance of travelling to find food, the frequency of drinking and their walking ability) can provide assistance to range managers for making the right management decisions and improving sheep and goat performance (Malechek & Provenza, 1983; Squires, 1984). Goats have been considered more efficient in the digestion of crude fibre and the utilization of poor roughages than sheep (Malechek & Provenza, 1983; Squires, 1984; Gihad et al. ). Possible physiological and behavioural factors for this ability of the goat have been indicated (Louca et al., 1982). However, with medium and good quality forage and adequate feed availability goats apparently are similar to sheep (Malechek & Provenza, 1983; Huston, 1978).
Nutrition and reproduction
Inadequate nutrition, particularly of energy, depressed the reproductive performance of extensively (H.F.R.O.,1979) or intensively managed sheep (Orskov, 1982) and of Indian breeds of goats (Sachdeva et al., 1973). Sexual maturity of sheep and goats is advanced by good feeding (Owen, 1976) and the energy stimulates oestrus activity within the normal breeding season, ovulation rate, fertilization and survival of ova and the maintenance of the resultant embryos to term as viable lambs (Gunn, 1967).
Body condition at mating, achieved over a longer period i.e. the period between one reproductive cycle and the next, has a greater effect on ovulation rate and barrenness than flushing (i.e. increasing the level of nutrition in the immediate pre-mating and mating period) (Owen, 1976; Gunn & Doney, 1975). High producing dairy ewes or goats, require a dry period to achieve maximum prolificacy.
The level of feeding after weaning of female lambs or kids intended for replacements depends on the age at mating. Usually lambs or kids are mated for the first time when they reach 60–80% of their mature weight. This weight is accomplished with proper feeding and management at the age of 8–10 months in France, Norway and Cyprus (Morand-Fehr, et at., 1982; Skjevdal, 1982; Maurogenis & Constantinou, 1983). In France (Blancnart & Sauvant) and Norway (Skjevdal, 1982) tables have been published with recommendations of dietary allowances for breeding female kids at the age of 7–9 months of age.
Nutrition and pregnancy
There is a very slow growth of foetus during the first 100 days of gestation (Blanchart & Sauvant, 1974; Economides, 1981) with more than 80% taking place during the last 8 weeks of gestation. Stress in pregnant goats during late pregnancy increased with increasing kidding percentage as indicated from the total birth weight of kids as a percentage of the dam's weight which was 8, 13.5and 18.5for goats giving birth to singles, twins or triplets, respectively (Economides & Louca, 1981). Foetal energy requirements in the final stage of pregnancy are 1.5MJME/kg foetus/day (H.F.R.O.,1979). This means that a 50 kg ewe carrying twins would have an energy requirement of about 2.5 to 3 times that of a non-pregnant ewe. However, these full requirements are not recommended and 25% lower requirement would reduce birth weight of lambs by only 10% which is acceptable on both biological and economic considerations (H.F.R.O.,1979). Low levels of energy during late pregnancy lead to pregnancy toxaemia particularly with goats (Economides & Louca, 1981;Morand-Fehr & Sauvant, 1979). However, high levels of feeding through pregnancy can lead to pregnancy toxaemia in sheep (Orskov, 1982) and kidding difficulties. The performance of Damascus goats in the last stages of pregnancy was similar with either medium (15.7MJME/ day) or high (20.1 MJME/day) levels of energy, but a low level of energy (11.3MJME/ day) resulted in pregnancy toxaemia (Economides and Louca, 1981).
Nutrition and lactation
Lactating sheep and goats have increased requirements for all nutrients. Different methods of estimating milk yield in sheep and goats have been developed which are useful in evaluating the results of various management systems. The lamb suckling technique or the use of oxytocin and milking have been widely used to obtain information in the non-dairy ewe (Owen, 1976) whereas with dual purpose sheep and goats a combination of the suckling technique and milking until weaning is used (Economides, 1984). Hand or machine milking after weaning have also been used (Morag et al., 1970).
Energy intake is the most important factor determining milk production in intensive systems, particularly in the early stages of lactation in sheep and goats (J. C. Flamant, et al., 1982; P. Morand-Fehr, et a!., 1980) but also under extensive systems (Fig. 1 & 2). Similarly under semi-arid conditions in Mexico (Martinez-Parra et al., 1981) and India (Shiarma, 1982) the milk yield of goats is positively related to energy intake.
Pregnancy nutrition in sheep has only a marginal effect on subsequent milk production when grazing on high quality pasture or high level of feeding in early lactation (Peart, 1967);similarly pre-partum energy levels did not influence the performance of Damascus goats in early lactation (Economides & Louca, 1981) when offered a high level of energy (27.8MJME/goat/day) during lactation. However, the milk yield of high yielding dairy goats (Skjevdal, 1982; Morand-Fehr & Sauvant, 1980) was improved by higher levels of energy intake in late pregnancy becuase of the building up of body reserves and their mobilization in early lactation to produce milk. Under such conditions a protein supplement is also necessary.
NUTRITION OF LAMBS AND KIDS
Birth to weaning
The weight gain of suckling lambs (Owen, 1976; Economides, 1984) and kids (Morand-Fehr et al., 1982) is closely associated with the level of milk intake during the early stages of the milk feeding period and declines with declining milk production. One unit of lamb liveweight gain results from 5 units of sheep milk consumed (Economides, 1984; Robinson et al.,1969), while one unit of kid liveweight gain results from 7 kg of goat's milk (Economides, 1982).
Weaning of lambs and kids can take place from 4 weeks to 5 months of age, depending on the management system. With either artificial rearing or natural suckling the success of early weaning systems onto solid food depends on the state of rumen development at weaning which is governed by the ingestion of solid feed. Solid feed intake is negatively related to milk intake (Economides, 1984; Owen et al., 1969) and after the age of 3 weeks milk should be offered less than ad libitum. Good quality creep feed and roughage should be available to lambs and kids from the age of two weeks.
When the milk supply of ewes or goats is inadequate or absent or when it is necessary to remove the progeny as part of the management system artificial rearing is practised. The lambs or kids are given colostrum within 6–10 hours after birth (Peart, 1982) and weaning within 24 hours after birth is ideal; later weaning increases difficulties of training the lambs or kids to suck from teats. Milk substitute can be given warm or cold (Penning et al., 1973) and should contain 20–25% protein and 25% fat for lambs (Orskov, 1982) and 16–24% fat and 20–28% protein for kids. Good milk replacers have conversion rates of milk solids into lamb gain of 1:1 and for kids 1.1to 1.3. With dual purpose systems and when artificial rearing is practised the amount of milk replacer fed until weaning is minimized, either with early weaning or restricted milk intake, in order to reduce feed and labour costs. When natural suckling is practised the adoption of early weaning and partial suckling with the objective of increasing commercial milk yields is of great importance. However, the growth of the offspring should not be affected by the lower milk consumption.
A series of experiments carried out in Cyprus (Louca, 1972; Lawlor et al., 1974; Louca et al.,1975; Hadjipanayiotou & Louca, 1976; Economides, 1980, 1982, 1984) showed that early weaning of lambs (0,2or 3 as compared to 35 and 70 days) adversely affected total milk yield of sheep and particularly of the low yielding breed (i.e. the Cyprus Fat tailed sheep). However, the beneficial effect of suckling did not extend beyond the time of weaning. A combination of partial suckling (12or 8 h vs 24 h a day) and residual milking can maintain the amount of milk available for commercial purposes without affecting the lamb growth rate. Total milk yield of Damascus goats was not significantly affected by the length of the suckling period (2,35 or 70 days) or suckling regime (continuous or restricted) but commercial milk yield was increased with either early weaning or restricted suckling. However, the growth rate of kids either weaned at 35 days of age or partially suckled from 20 to 70 days of age was poorer than that of kids suckled ad libitum until the age of 70 days.
Comparative trials with lambs and kids (Economides, 1982) showed that lambs grow faster both before and after weaning. The kids could not be weaned as early as lambs and suffered a greater check in growth at weaning than lambs. The growth data and feed intake data suggested that the rumen of lambs develops and begins functioning earlier than kids.
Weaning to slaughter
The performance of lambs grazing poor pastures is low because of low feed intake (inadequate feed supply and low quality roughage) resulting in low energy intake. The importance of adequate nitrogen intake in relation to energy intake for the performance of lambs (Egan, 1965; Orskov, 1977; Kempton & Leng, 1980) and kids (Morand-Fehr et al.,1982; Economides, 1982) has been extensively studied. Feed intake, daily gain and feed efficiency of lambs were improved considerably (Table 1) by supplementing a low quality roughage diet with protected protein and glucose infusion directly into the abomasum (Economides, Leng & Ball, unpublished).
It is apparent that sheep and goat fattening must be based on diets of high energy concentration and adequate in protein. The protein requirement of male lambs declines from 18% crude protein in the dry matter in the early stage of life to 12% at liveweights above 40 kg (Miller, 1968; Andrews and Orskov, 1970) while those of female lambs are about 2% units lower. Male kids responded linearly to increased protein level in the diet (Louca & Hancock, 1977; Mavrogenis et al.,1979) whereas female response was marginal. Growth response of kids to level of protein tend to decline at higher liveweight and/or age than lambs.
When urea was substituted for soyabean as the protein source for lambs carcass gain, feed intake and feed efficiency were reduced during the period from 2 weeks to 3 months of age. From 3 months of age to 45 kg liveweight only feed efficiency was reduced by urea (Economides, 1981).
The physical form of concentrate diets affects efficiency which is lower on a mash diet than on pelletted or whole grain diets for both lambs (Economides, 1983) and kids (Economides, 1984).
The slaughter weight of lambs and kids depends on the desired carcass quality and on seasonal price trends and also on the liveweight which minimizes total cost per kg carcass. Generally lambs are slaughtered at about half the mature weight of the parents, whereas in the United States lambs are slaughtered at even higher liveweights. With increasing carcass weight the fat content and calorific value of carcass increase and water content, ash and protein contents decrease (Morgan & Owen, 1973). The dressing percentage and chemical fat content were increased by fattening in the feedlot (E.S.E. Gaili, et al., 1972) and diets deficient in protein increased the fat to lean ratio in growing lambs (Andrews & Orskov, 1970). Goat carcasses have less fat than those of lambs (E.S.E. Gaili, 1972; A.H. Kirton, 1982). Females have fatter carcasses, at the same liveweight, than males with castrates intermediate. Castration leads to reduced growth rate, a fatter carcass and reduced feed conversion efficiency (Louca et al., 1970). However, a taint of varying intensity was present in the meat of intact goats but not in that from the castrates. Where feeding conditions are good ram lambs and male kids can often be slaughtered before there is any need for castration.
MANAGEMENT OF SHEEP AND GOATS
The aim in sheep and goat feeding is to feed as much forage as possible and satisfy the largest part of requirements. The quantity and quality of roughage available will determine the amount and type of supplement to be fed. The higher the quality of the roughage, the higher the intake and performance with sheep or goats on all roughage diets. The voluntary intake of lactating ewes and goats is 50 to 100% higher than dry animals (Peart, 1982). The level of feed intake immediately after parturition is low but it increases steadily after parturition and maximum intake is reached 2–3 weeks after milk yield peaks. Small amounts of nitrogen (soyabean meal or urea) and energy (grains) increase both the roughage and the total digestible energy intake.
Management of sheep and goats during the reproductive cycle
With one lambing every year the time between weaning and mating should enable ewes to replenish losses from the previous lambing. It is not advisable to improve nutrition, for example before mating only, resulting in higher ovulation and conception rates without making provision for the additional nutritional needs in late pregnancy and early lactation. The most criticial parts of the reproductive cycle must be corrected and not just at mating, or late pregnancy or early lactation.
In intensive sheep and goat systems feeding is based on the nutrient requirements of the animals and the nutritive value of feeds with the formulation of a ration which meets the daily requirements of the animals. Under these conditions feed intake of sheep and goats can easily be measured and available feedstuffs can be given in quantities needed to maintain good body condition. For example at the declining stage of lactation feed is offered according to milk yield. Twin suckling ewes are fed separately from single suckling ewes, or yearlings. During late pregnancy better nutrition is given to yearlings and leaner ewes and early and late lambing ewes and goats are also fed separately. Sheep and goats in intensive systems may rely on large quantities of crop residues or on small quantities of roughage and crop residues with higher quantities of concentrates. The use of concentrates is justified only if local meat and milk prices are high.
With semi-intensive and particularly extensive systems of management supplementing grazed roughage which varies in quantity and quality is a problem. In temperate climates there is usually adequate pasture and supplementation arises only when there is overstocking or when the time of lambing is changed for example with lambing at the end of the grazing season. In highlands as well as in tropical, semi-arid and arid regions the production of roughage is seasonal and varies widely both in quantity and quality. Under these conditions grazing sheep and goats respond to energy, protein and phosphorus supplements when grazing poor quality roughage and vitamin A when animals subsist on dry roughage for more than 4 months.
There is no doubt, particularly with extensive systems of management, that the situation can be improved with increasing the feed resources. Either by increasing the available land and thus increasing roughage production or by improvement of the existing land for increasing production or by supplementary feeding. In addition to increased roughage production and supplementary feeding, improved flock management is necessary. Stocking rate must be decided according to the animal carrying capacity at the worst time of the season, unless supplementary feeding is available at times of roughage scarcity. Part of the existing pasture can be improved and fenced. This area is reserved for grazing when most needed. In these improved areas animals may be brought at mating, during late pregnancy and early lactation. Leaner ewes or ewes suckling twins and yearlings can also make use of the reserved areas. When the quantity of pasture produced from this improved and reserved pasture is not adequate, crop residues, hay, silage and concentrates are used to supplement the animals at times of need.
Crop residues and agro-industrial by products
Crop residues and agroindustrial byproducts can play an important role in the feeding of sheep and goats in all management systems. Such residues can supply a substantial part of the maintenance requirements of all ruminants in the Asian region (Jayasuriya, 1985). Usually their nutritive value is low, mainly because they are deficient in nitrogen and energy. They have to be supplemented when fed to ruminants or their quality must be improved before feeding.
Cereal straw is an important roughage resource and it's nutritive value can be improved with nitrogen supplementation (Hadjipanayiotou et al., 1975), ammoniation (Sundstol et al.,1978), urea solution (Hadjipanayiotu, 1982; Tayasuria & Perera, 1982) and chemical treatment (Klopfenstein, 1978).
The use of poultry litter in the diets of ruminants is possible provided it contains no pathogens, drugs or other medicants (Hadjipanayiotou, 1982; Shah and Muller, 1983).
Machine milking of sheep and goats
Work at the Cyprus Agricultural Research Institute showed that machine milking in sheep results in a reduction of milk yield (7 to 21% ) and a decrease in the fat content of milk. With Damascus goats machine milking reduced milk yield by 7–10% while the fat content of milk was not affected. When milk yield per sheep per milking varied from 140–700 g, hand milking was more efficient, but above this level machine milking was more efficient. Ommission of one daily milking caused a 22% reduction in the milk yield of Chios sheep compared with 1% in Damascus goats (Papachristoforou et al., 1982).
Intensification of production can lead to nutritional disorders because animals are of higher productivity, they are fed unusual diets (high in grains) and there are frequent changes of the diets. Such disorders are acidosis, remenitis, pregnancy toxaemia, hypocalcaemia and copper poisoning. Underfeeding during late pregnancy will result in pregnancy toxaemia in sheep and goats. Any stress resulting in anorexia and thereby inadequate energy intake will precipitate this disorder. Dairy sheep and goats, because of prolonged lactation, may have depleted calcium reserves and a constant supply of calcium with the diet is needed to replenish calcium losses (Economides, 1984).
This type of feeding trough (protected to prevent faecal contamination) and diet supplementation with lasalocid sodium (37 mg/kg feed) provided adequate protection from coccidiosis and improved the rate of growth and feed efficiency of kids but had no effect on lambs (Economides, 1984).
The present level of productivity of goats and sheep in developing countries is generally low, mainly because of underfeeding, poor management and disease (Devendra, 1979, 1980). Productivity is also low in highlands because of seasonality of roughage production and it's low quality (H.F.R.O.,1979). There is no doubt that considerable increase in animal production can be achieved with improved nutrition and management practices under different production systems and systems of management. For example total edible meat of goats in Malaysia was increased by 40% when improved nutrition and management was applied in goats of the same breed (Economides, 1984). In Syria under pastoral conditions the mortality of sheep from drought has been eliminated and feed conversion efficiency of lambs was improved from 6to 3 kg per kg liveweight gain in intensive fattening units (Draz, 1983). Under the harsh environmental conditions of Scotland lambing percentage has been increased from 60 – 65% to 80 – 85%, liveweight per lamb sold was increased by 1 – 2 kg and the number of breeding animals has also been increased (H.F.R.O., 1979). In Cyprus with early weaning systems, fattening on balanced diets and slaughtering at higher liveweights meat production can be doubled from the same number of breeding animals compared with the production under the traditional extensive system of management 30 years ago.
It is true that during the last 20 years extensive scientific progress has been made towards increasing the efficiency of production of small ruminants. However, research findings have not been fully tested or adopted by the farmers either because some of the data obtained in developed temperate countries are not appropriate for the developing countries (semiarid, arid and tropics) or there is a weakness in the institutional frame work for providing technical advice. Weaknesses in providing credit for the application of new technology and lack of organization of the market for the protection of the animal production also inhibit adoption of new methods.
Increased production from sheep and goats can arise from an increase in animal populations. However, an inventory of existing feed resources in relation to animal numbers in each country is necessary. Having in mind what feeds are available and what is the present level of productivity of animals new technologies and research findings can be put together and tested in different production systems to evaluate and select the best systems suited to a particular region within a country under certain conditions.
Immediate results in increasing efficiency of production can be obtained with improved nutrition and management practices and disease control. All breeds respond positively to better nutrition and management practices but there are limits set by genotype. The economic response, however, to improved environmental conditions is higher with sheep and goats of high genetic potential.
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TABLE 1. The effect of supplementing a poor roughage diet with protected protein and/or glucose
Basic diet = poor quality oat chaff, urea, sugar, minerals and vitamins
Fig. 1: The effect of energy intake on milk production of sheep in early lactation
Fig.2: The effect of concentrate intake on milk production in goatsk in early lactation (Fehr & Sauvant,1980)