Dietary fat and adipose tissue metabolism in ruminants. Comparison with pig and rodents

Abstract

Effects of dietary fat on energetic efficiency, fat corrected milk, energy balance, body weight (BW) gain and change in body condition score of dairy cows are reviewed. Dietary fat did not affect gain in BW or body condition score after peak lactation but tended to increase BW loss during early lactation, increased the calculated energy balance of the cows, and tended to increase body fat deposition in growing cattle. Dietary fat decreased de novo fatty acid synthesis in adipose tissue, without changing lipoprotein lipase activity and total fatty acid esterification. Basal free fatty acid release from adipose tissue in vitro and beta-adrenergic lipolytic responses were increased by protected polyunsaturated fatty acids. When fat was fed to growing pigs, body fat increased in a thermoneutral or hot environment. Dietary fat increased energy intake and milk fat secretion and decreased BW loss in lactating sows. Dietary fat decreased de novo fatty acid synthesis and basal glycerol release in adipose tissue and tended to increase beta-adrenergic lipolytic responses simultaneously to increased membrane fluidity and decreased phosphodiesterase activity. Dietary fat increased body fat in rats. Polyunsaturated fatty acids were sometimes less efficient than saturated ones in increasing body fat. Lipoprotein lipase activity in adipose tissue decreased. Hepatic fatty acid synthesis was decreased sharply by polyunsaturated fatty acids, and adipose tissue response was less important. beta-adrenergic-stimulated lipolysis decreased, and fatty acid esterification increased, particularly from saturated fatty acids. A trend toward insulin resistance which was more marked with saturated fatty acids, occurred in adipose tissue.