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THE EFFECT OF FEED RESTRICTION ON SMALL STOCK

P G Marais

Grootfontein College of Agriculture, Middelburg Cape Province,

5900



The effect of various degrees of feed restriction on subsequent compensatory gain in small stock has been studied by various researchers and contradictory results have been obtained. These contradictions may possibly arise from the effect of differences in age, gender, voluntary feed intake, in body composition and efficiency of feed utilization. In this paper experimental results of three trials are evaluated, not only from the performance and efficiency of feed conversion, but also from the body composition viewpoint. Physiological age and the time treatments applied are important. Sheep subjected to feed restricted soon after birth are likely to exhibit compensatory growth to varying degrees, depending on the previously imposed restriction. It is clear that the deposition rate of protein and fat decreased progressively in lambs as restriction during the restriction phase increased. After a period of feed restriction, the deposition rate of protein and fat increased in all experimental groups comprising lambs. In general, gender differences in the deposi- tion rate of protein and fat do occur during the restriction and realimentation phases. It also seems clear that feeding level did not affect the fat:protein ratio of ewe and ram lambs. As expected, the ratio of ewe lambs was greater than that of ram lambs. As the restriction increased, the efficiency of energy conversion declined, while the efficiency improved with an improvement in feeding level. The efficiency of ram lambs was constantly better than that of ewe lambs. The results indicate that when the total amount of protein or fat or fat:protein ratio is taken as the criterion of body composition when examining the effect of feed restriction and compensatory growth, no significant differences between feeding levels were found. On the other hand, when deposition rate of protein or fat together with an increase in body mass, is taken as criterion, compensatory growth is only exhibited by ram lambs after a period of feed restriction. The evidence presented indicates that nutritional restriction does not always produce a subsequent compensatory response. The compensatory growth response is complex with a number of contributing mechanisms that interact to produce a co-ordinated response.

 

Published

Proceedings 30th SASAP congres, Agricultural news 22 April 1991