Effects of supplementation with safflower oil on voluntary feed intake and tissue fatty acid composition of steers fed low quality hay ad libitum

摘要

The effect of safflower oil supplement (200 mL/day) on voluntary feed intake and fatty acid composition of plasma, blood platelets, subcutaneous adipose tissue, and M. longissimus dorsi muscle was studied in Brahman steers consuming a low quality hay. The initial mean liveweight (LW) of the steers was 197 kg. Mean LW gain over 50 days was 20 kg for all steers, but voluntary feed intake (5.63 kg/day) was reduced by 1.02 kg/day with safflower oil. Supplementation increased the plasma concentrations of unsaturated fatty acids, indicating a less complete hydrogenation of dietary safflower oil than of hay by rumen microorganisms. Safflower oil altered the fatty acid (FA) profiles of platelet and muscle phospholipids. with increases in the proportions of monounsaturated acids (MFA) and polyunsaturated fatty acids (PFA) and associated decreases in the proportions of saturated fatty acids (SFA). The neutral lipids of adipose tissue consisted of 60% SFA and 38% MFA in steers fed hay alone, compared with 53% SFA and 45% MFA in supplemented steers. Safflower oil had no effect on the total fat content of muscle; the concentration of PFA was not significantly altered, but SFA decreased 17% in parallel with a 23% increase in MFA. The results support proposals that dietary oil supplements may be used to reduce forage intake during dry season or drought, to conserve body protein and to modify the FA composition of meat phospholipids which may, in turn, influence meat quality of ruminants consuming low quality roughage diets.