Sheep - AgRIS

allied to the various amino acids of which the protein is composed. Some amino acids may be
synthesized in the rumen. All proteins contain nitrogen, carbon, hydrogen, and oxygen, and
some also contain phosphorus, iron, and sulphur.
The percentage of protein contained by the dry matter of feeds used for sheep varies from
about 5 to 20 in the case of roughagnes up to around 45 for some ofthe concentrates. Among
the best sources of proteins are the leguminous plants which form such an important element in
the pasture and agricultural industry. These plants are able to make use of the nitrogen of the
atmospherej which constitutes such an important element of soil fertility.
The protein is needed for maintenance of existing body structure, growth of tissues and
organs, reproduction and production of milk and fibre. Protein is the basic structural material of
all the body tissues and is required for regeneration of living tissues which are subjected to
constant destrustion and repairs. The breeding animals need protein for pre-natal growffi,
development of the foetus and to produce milk for post-natal growth of young ones. Clean
scoured wool comprises of keratin which is almost a pure protein. If the ration does not contain
enough energy, the protein will be used as energy source. But protein cannot be repalced by
any other nutrient in the ration. Protein deficiency causes reduced feed intake and poor feed
efficiency. This would result in poor growth and development of muscle, reduced reproductive
efficiency and wool production. The protein deficient animals have lower disease resistance
due to smaller amount of immune protein.
Although proteins vary in their nitrogen content, in the usual method of analysis, nitrogen
content of sample is multiplied by 6.25 and is termed crude protein (CP). Many other
nitrogenous substances which are not true proteins are also present in feed and these are often
called non-protein nitrogen (NPN). Some of NPN compounds present in feed are amines,
amino acids, ammonia, nitrates, nitrite, pigments, urea and vitamins (nicotinic acid).
In several countries requirement of protein is expressed in terms of CP. Under Indian
conditions, it may not, however, be applicable because of many unconventional feeds being
used which have very low digestibility of protein although the crude protein content is
reasonably high. Hence the digestible crude protein (DCP) content of the diet is more important
than the crude protein content. The approximate daily requirement of DCP for maintenance is
1/10th of the TDN or 1 g for every 1 kg of live weight. This requirement will increase by about
50 per cent during preqnancy and by 100 per cent during lactation and growth. A 30 kg sheep
will thus require 30 g DCP during dry non-pregnant stage, 45 g during last 6 weeks of gestation
and 60 g during first 10 weeks of lactation. Protein quantity is more important than quality in
the sheep ration because the rumen microbes can convert a low quality protein to high quality
amino acids, although the availability of some suplphur containing amino acids, e.g.
methionine and cystine, could become a limiting factor in woolly sheep.
Sheep require liberal amounts of proteins\for growth, for the replacement of body tissues
and fluids, for reproduction, and for the growth of wool. Sheep can subsist on feeds partially
deficient in protein, but they cannot give maximum production. The protein requirements of
pregnant ewes is very high, much higher than in beef cattle, for sheep reproduce in a shorter
time and often have two or more lambs, which represent a large percentage of the body weight
ofthe ewes. It has been shown that the daily protein requirement for wool growth alone is from
0.04 to 0.06 kg per 450 kg of live weight. Since the wool fiber is chiefly protein, and the
demands for protein for other purposes is high, the significance of a diet adequately supplied
with this nutrient is evident. In general, sheep are unable to produce protein from other
materials. However, it has been established that a nonprotein nitrogen compound, urea, may
serve as a source of protein for ruminants because ofthe utilization of the urca nitrogen by some
of the bacteria and protozoa in the digestive tract of such animals. The bacterial and protozoan
proteins are then utilized by the sheep.
The ration of sheep should contain at least 9 or 10 per cent protein, preferably 13 to 14 per
cent, and it has been observed in many cases that a much higher intake increases the rate at
which lambs grow and fatten. If the protein is insufficient, the most obvious symptom is a
decline in the appetite for feed and a slowing up or a cessation of growth, together with a very
poor development of the muscles in growing lambs. In mature ewes there is a lack of thrift and
poor wool growth; there may also be some impairment of reproductive functions shown in the
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