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Nutrient Requirements
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Sheep and goats are kept primarily under extensive farming conditions, making use of lower-cost roughage sources which fluctuate substantially in production according to area and rainfall. Management styles are very different when comparing the arid Karoo, with its typical short bush interspersed grass dependent on 250 mm rain and less, to management styles used in the eastern Highveld, with its extensive grasslands and grain production capabilities due to a rainfall of 600 mm and over in normal years.
The majority of sheep and goat producing farms are based on low-cost pastoral grazing. It is obvious, therefore, that a satisfactory return on investment would be achieved only where land price and productivity are proportionately competitive.
Digestive System
The digestive tract in the pig and dog is comparatively simple, although differences occur in digestive juice secretions.
However, in both species’ saliva is secreted by the parotid gland, submaxillary and sublingual glands. The saliva contains the starch-splitting enzyme ptyalin. Gastric juices in the stomach are secreted by the pyloric and fundus glands which form a villous coating.
The digest is strongly acid and contains lactic and afterwards, hydrochloric acid. The breakdown is accomplished by the action of enzymic hydrolysis. Monogastrics are less versatile in assimilating food and are dependent on regular intakes of a complete range of nutrients.
Pepsin is secreted in the mucus membranes of the stomach to hydrolyse proteins. From the pancreas is secreted trypsin and chymotrypsin, carboxypeptidase, aminopeptidase and di-peptidase from the small intestine, all for protein hydrolysis.
Fats are hydrolysed by stomach lipase and pancreatic lipase.
Glucosides are hydrolysed by such enzymes as maltase, lactase, sucrase and glucosidase from the small intestine.
Most of the digestion in these animals takes place in the stomach and overflows into the small intestine. While the starches and sugars are digested first, the proteins take longer to be digested. The chief area for absorption is the small intestine. Actually, fibre is poorly utilised by pigs, dogs and cats.
The pig is, however, capable of limited bacterial fermentation in order to cope with grazing and limited consumption of lucerne hay.
Water Needs for Sheep
The daily access to water for drinking purposes is a basic need not infrequently neglected, especially in the semi-arid sheep country. Judging from appearances, it would sometimes seem as if the only available water to sheep in the area is the morning dew.
The water consumption of sheep is influenced by many factors, such as ambient temperature, rainfall, activity, wool covering, age, succulence of feed, the plane of nutrition and lactation. Sheep that suffer from thirst will eat less, lose mass and naturally produce less milk for their lambs.
Pregnant ewes are fed on a high plane of nutrition twice as much water as ewes fed at a maintenance level.
When on dry winter-veld grazing the water consumption of sheep is much less than when the same sheep receive adequate rations. However, a good policy is to provide about 5 l of water per sheep per day.
Due to the possibilities of internal parasitic infections, open, muddy watering places should be avoided. In the arid sheep areas, it is advisable to have the borehole waters checked in order to ascertain whether harmful mineral salts are present.
Feeding Sheep
Because wool growth is a continuous process, maintenance and sub maintenance feeding would apply only in abnormal circumstances where it has been decided to forfeit the fleece and try to save the animal from dying of poverty. These terms would, therefore, be more applicable to mutton types of sheep or valuable breeding animals.
It appears that the daily total protein needed by Merino ewes weighing 35 kg would be about 75 - 80 g. The digestible protein level would be about 55 g per day.
The digestible energy need is approximately 2.5 – 3.0 MCal per day. Actually, ordinary mature flock sheep fare satisfactorily on a daily intake of 1.5 MCal.
The daily phosphorus requirements as given in the NRC tabulations are considered to be liberal as 1 – 1.5g P per sheep per day gives the best results locally.
If it is assumed that a small flock of Merino ewe weigh 32 kg and produces a fleece of 3.6 kg per annum, or about a yield of 6 g clean wool per day, plus a lamb for which she gives 1l milk daily, her daily nutritional needs would be met by 68 g of crude protein, 3 MCal, 1 g of phosphorus (P), 8 g of common salt (NaC1). The requirements, however, escalate in bigger framed sheep with higher growth and reproductive capacity.
The increase in requirements of the ewe, from maintenance to pregnancy and eventually to lactation, escalates the requirements manifold. Furthermore, the lamb, at half the body mass of the ewe, at maintenance level, has nutrient requirements that are more than double per kg of body mass.
Under maintenance conditions for ewes, the nutrients supplied by natural grasses are adequate or almost adequate. However, when production and reproduction requirements are taken into consideration, the situation changes substantially. Either these increases in requirements are met or productivity declines.
On pasture or veld grazing a lack of energy is to occur. This is due to various factors such as insufficient feed intake during winter or droughts, the unacceptability of hard, lignified, low-quality roughage, even if a sufficient amount of such poor roughage were to be consumed, its lower digestibly would result in an energy deficiency in the animal.
In the case of sheep that are required to walk while grazing on pastures or in the veld, the energy requirement is estimated to be 24 — 77% (NRC) higher than for stall-fed sheep.
A low level of energy intake is probably one of the main causal factors for the general light mass of Merino sheep on the open range. Such low energy levels result in low fertility, weak lambs, the poor milking ability of ewes and their frequent refusal to suckle their lambs. Susceptibility to disease infection and internal parasite infections is also more common in underfed sheep.
In stressing the value of energy supplementation, a warning should be sounded that in doing so the level of other nutrients should be raised as well for the best results to be obtained. From observation and experience sheep, are able to subsist on 112g of maize for a comparatively long period during a drought.
The above simple formulation is mixed with a shovel on a concrete floor and placed in cut drums in the camps for easy access by the grazing sheep. The inclusion of a small amount of molasses or maize meal is to assure acceptability. A rate of voluntary intake of approximately 20g per sheep is anticipated.
When the pasture declines, due to colder months and lowered rainfall, it becomes necessary to increase the supplementation rate by reducing the salt content and increasing the number of ingredients.
Ration Balancing for Sheep
The following calculation shows how to balance a ration for sheep by utilising low-quality roughage and a high protein concentrate. We are interested in formulating a ration for a ewe that is in her first eight weeks of lactation with a single born.
HPC: HPC stands for High protein concentration.
For the purposes of the calculation presented here a number is provided (in brackets) associated with each value. Let the facilitator help you with that when you do the activity. The ration should include HPC40 if the preliminary ration does not include at least 60% of a legume roughage (see tip for selecting of preliminary ration). Utilise The Nutrient Requirements of sheep and Table 2 Composition of Feedstuffs that follows.
Tips for the Selection of a Preliminary Ration
Legume hay more than 50% of roughage: Leave HPC from the preliminary ration. Legume hay only source of protein:
- Legume hay should then constitute at least 60% of the roughage.
- Legume hay replaces urea free HPC in step 5. Add calculations 14 and 40.
Hay other than legume hay:
- Include HPC in the preliminary ration.
- HPC with urea, use a maximum of 6.5% HPC.
- HPC without urea, use 10% HPC.
Preliminary estimation of energy in ration: The table below shows the low energy content roughage (7.5 MJ/kg ME) in the ration with a corresponding expected energy content of the ration.
- When HPC 60 is used, use 5% less roughage.
- When higher energy content roughage (8.1 + MJ/kg ME) is used, use 5% more roughage.
- Prevent disturbances: Roughage should preferably be not less than 40% and definitely not below 20%.
- Protein and energy should rather be slightly oversupplied rather than undersupplied.
When silage is given to sheep:
- Calculate the ration on a dry basis.
- Multiply the quantity (%) by three to get it on an as fed basis.
- The ratios will then be in kg and not percentage.
- Silage should preferably not be more than 40% of the roughage on a dry basis.
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