Lipogenesis in the Ruminant: in vivo Site of Fatty Acid Synthesis in Sheep

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Abstract
In vivo experiments were conducted to quantitatively assess the lipogenic capacity of various tissues. Both growing lambs and market weight lambs were injected with acetate-1-14C, killed at 15 or at 30 minutes after dosing and the incorporation of radioactivity into fatty acids by various tissues was determined. Adipose tissue was the predominant site of fatty acid synthesis. Liver, rumen, abomasum, and small intestine tissues combined contributed only 8% of the total fatty acids synthesized. The low rate of lipogenesis by liver is consistent with the theory that the primary function of ruminant liver is gluconeogenesis. Comparison of seven adipose tissue sites indicated that the greatest incorporation of acetate into fatty acids on a tissue weight basis occurred in perirenal and omental adipose tissue in both groups of lambs. Various subcutaneous depots of adipose tissue (abdominal, shoulder, and backfat) as well as mesenteric adipose tissue were similar in lipogenic activity but significantly lower than perirenal and omental adipose tissue.