Soaking of complete fattening rations high in poor roughage. 4. The effect on deposition and fatty acid composition of bovine fat

Abstract

SUMMARYThe effects of diets containing variable percentages of roughage and moisture on depot fats were studied. Treatments were 25 and 45% roughage in the complete fattening diet, and 10, 50 and 75% moisture content of the diets. Depot fats collected post-slaughter from kidney, pelvic, ruminal, cod and trim fats in the carcass (mostly subcutaneous and some intermuscular) were weighed and analysed for their fatty acid composition.Increasing the quantity of roughage in the diet (from 25 to 45%) significantly decreased ruminal fat deposition. Moistening the feed significantly increased the deposition of kidney, pelvic and cod fat, and significantly reduced the deposition of fat trim in the carcass. The content of unsaturated triglyceride fatty acids was significantly greater in calves fed on the 25% roughage diet. Calves fed on the soaked diets had significantly higher contents of unsaturated fatty acids than the controls.The content of unsaturated acids was greater in cod fat and carcass trim than in kidney, pelvic or ruminal fat.Hydrogenationin vitroof fatty acids by ruminal micro-organisms decreased with increasing level of moisture in the diet.It is suggested that the increased unsaturated fatty acid content of the depot fats of animals fed on soaked diets might be due to a reduction in the hydrogenation of dietary lipid by rumen micro-organisms.