Plant and animal factors affecting the diet selection of sheep

• Main Author: Cooper, Susan Dianna Barbour
• Published: University of Edinburgh 1995
• Subjects: 636.085
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.643419

The purpose of this work was to test the ability of sheep to select between foods of different energy density (ED; MJ ME/kg food) a diet which meets their physiological needs, in a series of five experiments. Experiment 1 used pregnant and contemporary non pregnant ewes to test the hypothesis that sheep can select a diet which meets their needs for energy and protein. Four foods were offered: foods A and B were of high ED and foods C and D were of low ED; foods A and C were of high crude protein (CP) concentration, foods B and D were of low CP concentration. The treatments included paired choices of foods A and B, and foods C and D, which were offered to the ewes. The results showed that when the ED of foods is high, pregnant ewes select a diet that reflects their enhanced protein requirements, in contrast with non pregnant contemporaries. When ED is low, priorities other than physiological state may motivate dietary choice. It was suggested that such a priority is the maintenance of a balanced rumen environment. Experiment 2 and 3 tested the effect of ED of foods offered as a choice on the diet selection of sheep and the relationship between the rumen environment and the diet selected from a pair of foods of different ED. The diet selected by the choice fed sheep in Experiment 2 did not consist solely of the high ED food (H), but contained a substantial quantity of the low ED food (L). It was hypothesised that the diet selected by sheep from a choice of low and high ED foods is affected by the rumen conditions, specifically rumen pH and osmolality, and that sheep will alter their pattern of dietary choice to maintain optimal rumen conditions.