Cereal processing and food utilization by sheep. 3. The effect of replacing whole barley by whole oats on food utilization and firmness and composition of subcutaneous fat

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Abstract
SUMMARY: 1. Forty-eight early-weaned lambs were used in an experiment in which whole barley was gradually replaced by whole oats in order to produce different types of rumen fermentation.2. The type of rumen fermentation promoted by whole barley did not give rise to excessively soft fat in female lambs; in males, however, some carcasses were unacceptable. An increase in the proportion of propionic acid in the rumen liquor was associated with an increased proportion of odd- and branched-chain fatty acids and a decreased proportion of stearic acid in carcass fat. When the molar proportion of propionic acid in the rumen liquor was above 30%, three out of every five carcasses from the entire male lambs had excessively soft fat.3. Assessment of food utilization was complicated by lower daily intakes of digestible organic matter (DOM) when more than about 15% of barley was replaced by oats and also influenced by changes in gut contents. With 100% whole barley the mean gut fill was 4·7 kg while with 100% oats it was 9·4 kg.Assuming a maintenance requirement of 100 kcal metabolizable energy/kg0·75, it was calculated that the digestible organic matter of oats was utilized more efficiently than that of barley to produce empty-body gain. Most of the differences in utilization disappeared if an adjustment was made for differences in gut contents. The results indicate that the maintenance requirement/kg0·75 decreases with increasing gut content.