Protein protected fat for ruminants. IV. Plasma lipid, insulin and depot fat composition of lambs.

Fourteen crossbred lambs with an average weight of 29.4 kg were utilized to determine the influence of the nature and amount of dietary lipid intake on the qualitative and quantitative composit ion of the plasma lipid, carcass depot fats and plasma insulin levels. Formaldehyde treated casein-cottonseed oil (PCO) was supplemented at the rate of 8% (three lambs) and 12% (three lambs). Two groups of four lamb each were assigned to diets containing no added fat (control) and 8% unprotected cottonseed oil (8% CO). Dietary lipid supplementation was effective in elevating (P<.05) the lipid levels of the blood. No difference (P>.05) in plasma insulin levels were detected between the four diets. Oil supplementation increased (P<.05) the concentration of linoleic acid in the four plasma lipid fractions: cholesterol esters, phospholipids, free fat ty acids and triglycerides. Although not always statistically significant, the content of total unsaturates tended to increase (P<.05) in all plasma fractions. Subcutaneous fat biopsies obtained from the tailhead region at 0, 14, 42 and 84 days on feed revealed that the type of dietary fat fed was effective in altering the type of fat ty acids deposited subcutaneously. Feeding cottonseed oil protected from rumen fermentation elevated the linoleic acid levels of subcutaneous fat, but the total unsaturated fat ty acid levels were not different between diets. (