Effect of dietary sunflower oil and vitamin E on beef cattle performance, carcass characteristics and meat quality

In the present study, we tested the hypothesis that feeding sunflower oil (SFO) containing about 70% linoleic acid would increase conjugated linoleic acids (CLA) content of beef and that the increased CLA levels would improve meat shelf life. Two feeding trials were conducted to determine the effect of SFO supplementation on beef production, carcass characteristics and meat quality parameters. In addition, the visual aspects of beef quality in retail display as influenced by dietary vitamin E were compared with that of the increased CLA derived from dietary SFO. In exp. 1, 72 finishing steers (465 +/- 9 kg) were individually fed one of four dietary treatments: an unsupplemented control finishing diet, the control diet supplemented with 6% SFO, 500 IU head(-1) d(-1) vitamin E or a combination of 6% SFO and 500 IU head(-1) d(-1) vitamin E for 95 d. Data from in vitro gas production from the diets indicated that oil inclusion reduced rate and lag time prior to initiation of gas production. Dry matter intake (DMI) declined (P < 0.05) due to dietary treatments without affecting average daily gain or feed conversion efficiency. Meat from steers fed all supplements was less red, more discolored and less acceptable after,2 d storage in a display case. In exp. 2, 40 steers (412.5 +/- 11 kg), in individual pens, were used in a second completely randomized design experiment to evaluate the effect of supplementation of steam-rolled barley based finishing diets with 0, (CON) 3 or 6% SFO or 500 IU head(-1) d(-1) vitamin E on performance, carcass, meat characteristics, and fatty acid composition of beef. No difference (P > 0.05) in final liveweight, DMI, average daily weight gain (ADG) and feed efficiency (FE) of steers fed diets was found. Carcass grade fat was higher (P < 0.05) in steers fed the 6% SFO diet than the other diets. Retail acceptance score of meat obtained from steers fed 6% SFO was higher than from steers fed other diets (P < 0.05). In both experiments, the fatty acid composition of the meat indicated that C-16:0 and C-16:1 fatty acid levels were lower (P < 0.05) while C-18:2 was higher (P < 0.05) in longissimus muscle of steers fed 6% SFO than the other diets. CLA content in fat from longissimus muscle was higher in steers fed the 6% SFO than control diets (3.5 vs. 3.0 mg g(-1) in exp. 1 and 3.5 vs. 2.0 mg g(-1) in exp. 2; P < 0.05). Hence supplementing feedlot diets with SFO for up to 108 d can increase CLA composition of beef. Positional distribution of fatty acids indicated that the majority of the CLA was in the sn-2 position of the triacyglycerol molecule.