Effects of Added Dietary Fat on Fatty Acid Composition and Carcass Characteristics of Fattening Steers

Abstract

Eighteen steers in drylot were fed rations containing 0, 2.5, or 5.0% added animal fat. Samples of rib fat from each steer were analyzed for fatty acid composition by means of gas chromatography; similar determinations were made on fatty acids in the ether extractable portions of the rations. Measurements were also made in respect to a number of carcass characteristics. The addition of animal fat to the steer rations resulted in a significant increase in percentage of separable rib fat in those animals previously receiving a low-energy ration, but not in steers wintered on a higher-energy ration; a similar situation existed in respect to thickness of rind. The addition of animal fat to the rations resulted in a highly significant increase in stearic acid content of rib fat. Samples of rib fat from 20 pasture steers were also analyzed for fatty acid content. The deposition of myristic acid was significantly greater in steers receiving a grain ration with 10% added fat. The depression of the percent of oleic acid deposited in steers receiving implants of diethylstilbestrol was highly significant. It appears that the hormone depressed the deposition of palmitic acid in steers receiving added dietary fat, and stimulated such deposition in steers on a grain ration containing 7–10% salt; the condition was reversed in respect to palmitoleic acid deposition. The percent of palmitoleic acid was quite high in all samples of rib fat from pasture fed steers as compared to that from steers fed in drylot.