Enhancing beef conjugated linoleic acid content through oil supplementation to grazing steers
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Research was conducted to evaluate effect of increasing dietary linoleic acid through corn oil supplementation to grazing steers on beef conjugated linoleic acid (CLA) cis-9, trans-11 isomer content and on animal performance and carcass traits. First study: eighteen grazing Angus steers were supplemented with varying levels of corn oil (0% BW, NONE; 0.075% BW, MED; 0.15% BW, HI). Pelleted cottonseed hulls were used as a carrier for the corn oil. Oil supplementation had negative effects on pasture intake and digestibility, but not on animal performance. Oil supplementation increased carcass weight and fatness. Oil supplementation increased both CLA cis-9, trans-11 isomer and trans-11 vaccenic acid (TVA), except in the i.m. fat with HI where no differences were observed. Oil supplementation decreased myristic and palmitic acid proportions. Stearoyl-CoA desaturase activity and expression was not altered by oil level. Second study: 28 Angus steers grazing an endophyte-free tall fescue were supplemented with isoenergetic quantities of either corn grain (0.52% BW; PC) or soybean hulls plus corn oil (0.45 + 0.10% BW; PO). Negative (pasture only; P) and positive (85% concentrate: 15% roughage; C) control diets were included. PO, but not PC reduced pasture DMI; none affected total DMI. PC, but not PO affected NDF digestibility; none affected DM digestibility. PO and PC carcasses were heavier than P, but lighter than C. Carcass fatness was greatest in C; were fatter in PO than in P, being PC intermediate. Intramuscular fat was greater in C than in the grazing treatments; PO tended to be greater than P. CLA cis-9, trans-11 and TVA content were increased by PO, but decreased by PC relative to P; C had the lowest content. Stearoyl-CoA desaturase expression was greatest in C; greater in PO, but not in PC than in P. Total CLA cis-9, trans-11 and TVA content in LM were similar for P, PC and C, but higher in PO; myristic and palmitic acids were greater in C than in the grazing treatments. Corn oil supplementation to grazing steers not only has positive effects on performance and carcass traits, but also enhances beef CLA cis-9, trans-11 and TVA content.