Meat quality and fatty acid composition of pasture-finished beef steers fed barley and soybeans

Abstract

The effect of supplemention on the performance, carcass characteristics, meat quality, and fatty acid composition of pasture-finished cattle was studied. Thirty-two steers were assigned to four treatments in a randomized block design. Treatments were: totally mixed ration (TMR) [confinement-fed total mixed ration (60% grass silage, 40% rolled barley], pasture only (rotationally grazed temperate mixed pasture); pasture plus barley (the same pasture plus 4.5 kg DM hd-1 d-1 rolled barley) and pasture plus soybeans (the same pasture plus 1.8 kg DM hd-1 d-1 whole roasted soybeans). Steers were slaughtered after 105 d on test. Tissue samples were collected at slaughter for analysis of meat quality and fatty acid content. Dry matter (DM) intakes were greater for TMR-fed cattle (P < 0.05). Among the pasture-fed cattle those fed barley (P < 0.05) consumed more total DM than those given pasture alone. Rates of BW gain were higher for TMR-fed steers than those fed pasture only (P < 0.05). Carcass weights and dressing percentage were similar across all treatments. Feeding barley or soybeans on pasture increased backfat thickness (P < 0.05), but the pasture-only cattle had greater loin eye area (P < 0.05). Pasture-only beef had more thaw drip loss (P < 0.05) and less cooking drip loss (P < 0.05) than TMR-fed beef. Evaporative cooking losses were greater in beef from unsupplemented pasture than from barley- or soybean-supplemented pasture (P < 0.05). Pasture-only beef had 25% more polyunsaturated fatty acids and 37% greater cis-9, trans-11 conjugated linoleic acid (CLA) concentrations in longisimus thoracis (l. thoracis) tissue than TMR-fed beef (P < 0.05). Among pasture-fed cattle, soybean supplementation increased C18:2 concentration by 34% (P < 0.05), while barley reduced C18:3 concentration by 8% (P < 0.05) in l. thoracis tissue. Soybean supplementation increased cis-9, trans-11 CLA concentration by 30% (P < 0.05) in l. thoracis tissue over pasture only. Beef finished on pasture has higher levels of beneficial fatty acids than TMR-fed beef, with few differences in meat quality. Supplementation on pasture improves animal performance, but barley has some negative effects on beneficial fatty acids in meat. Key words: Pasture, steers, fatty acids, conjugated linoleic acid