Comparison of Several Enzymes and Components of Milk, Blood, and Tissues Between Cows and Ewes

Abstract

Two ewes and three cows were compared in certain biochemical parameters which might help to explain the greater content of protein and fat in milk of the ewe. Ewe's milk contained 1.25 times as much protein as cow's milk. The RNA/DNA ratio, leucine incorporation, acetate supply, and substrate supply (α-amino nitrogen) all were consistent with higher levels of protein in ewe's milk. The fat concentration in ewe's milk was 2.3 times more than that of cow's milk, and the activity of the glyceride synthetase complex in ewe mammary tissues was three times that of cow mammary tissues. However, lipoprotein lipase activity in mammary tissue of the cow was 13 times that of the ewe, although transfer of blood fat to milk was about the same for both species. Hepatic glyceride synthetase, adipose lipoprotein lipase, and fatty acid release from adipose tissue were greater in the cow than the ewe. Mammary tissue from ewes compared to cows removed more acetate from blood plasma but incorporated less 14C-acetate into lipid, which indicates a greater nonfat use of acetate by ewes. Mammary glyceride synthetase activity offered the only biochemical explanation for the greater fat content of ewe's milk. © 1969, American Dairy Science Association. All rights reserved.