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Increasing the Polyunsaturated Fat Content of Beef and Lamb

University of California^,2, Davis 95616

Abstract

A commercially prepared (Alta Lipids Ltd., Boise, Idaho) supplement containing lipids encapsulated in formalin treated protein was fed to lambs and steers. The supplement, containing 21% linoleic acid, was fed to the lambs as 40% of the diet. Weight gains were the same between supplement and control fed lambs (.20 kg/day). Feed intake (kg/day) and the F/G ratio were: supplement lambs 1.45 and 7.2; control lambs 1.68 and 8.4. Linoleic acid concentration of the subcutaneous fat biopsies averaged 3 to 4% for the control lambs throughout the trial. The value gradually increased in the supplement lambs to 11.6% at day 27, 17.0% at day 48 and 20.4% at day 69. Fat extracted from muscle tissue samples taken at slaughter had linoleic acid levels of about 5% in control lambs and 21% in supplement fed lambs. The major change in fatty acid composition of lamb fat was the increase in the linoleic with decreases in the palmitic, palmitoleic and oleic acids. The lipid and the crude protein in the supplement had digestion coefficients of 96.5% and 81.4%, respectively. The results of trials in which steers were fed diets containing 33% of the supplement, with various levels of concentrate, revealed that the amount of linoleic acid stored in the body fat was positively related to the consumption of metabolizable energy above the maintenance requirement. Steers fed a diet containing 1/3 roughage, 1/3 concentrate and 1/3 supplement had the greatest change in linoleic acid concentration in the subcutaneous fat. The levels (day of sampling given first) were: 9, 5.2%; 22, 8.2%; 51, 11.3%; 73, 11.8%; 114, 12.7% and 154, 16.77%. Control steers averaged 2.3% linoleic acid in the subcutaneous fat. The increase in linoleic acid in the adipose tissue was accompanied by a significant decrease (P<.05) in palmitic, palmitoleic and oleic acids.

¹ Department of Food Science and Technology.

² Department of Animal Science.