Effect of forage type with or without corn supplementation on animal performance, beef fatty acid composition, and palatability12

Thirty-two steers were used to examine forage type (legumes [Medicago sativa and Glycine max] vs. grasses [Lolium arundinaceum and Sorghum bicolor]) with or without individual corn grain supplementation (0 vs. 0.75% of live weight [LW]/d) on beef fatty acid composition and palatability. In each year, steers (n = 16/yr) were randomly assigned to forage type (n = 8/forage type per yr) and to supplementation treatments within forage type (n = 4/supplementation treatment/forage type per yr). Forage types (grasses vs. legumes) were replicated in 2 paddocks of perennial and annual forage type pastures. A mixed model was developed with forage type, corn grain supplementation, and the 2-way interaction as fixed effects and 2 different error terms, one for testing forage and another for testing grain supplement and grain supplement × forage interaction. Corn grain supplementation increased (P = 0.01) ADG by 0.29 kg/d and final LW by 13 kg. Hot carcass weight, dressing percentage (DP), and KPH were greater (P < 0.05) for steers supplemented with corn grain. Carcasses from steers grazing legumes had greater (P = 0.04) DP compared with carcasses from steers grazing grasses. Alpha-linolenic acid concentration was higher (P < 0.05) in LM of steers grazing legumes than in LM of steers grazing grasses, both without supplementation. Supplementation decreased (P < 0.05) linolenic acid levels for both forage types; however, the magnitude of this reduction was greater for legumes than for grasses. The ratio of n-6 to n-3 PUFA was greater (P = 0.03) in the LM of corn grain–supplemented steers than in the LM of nonsupplemented steers. Supplementation of corn grain decreased (P < 0.05) the percentage of odd-chain fatty acids and increased (P < 0.05) the percentage of MUFA in the LM. Warner–Bratzler shear force values were not altered (P > 0.05) by forage type, supplementation, or the 2-way interaction. Beef finished on legumes had greater concentrations of n-3 PUFA, whereas beef supplemented with corn grain had a greater ratio of n-6 to n-3 fatty acids. On a gravimetric basis (mg/100 g LM), n-3 PUFA and CLA contents were not altered with supplementation, indicating that corn grain can be supplemented at this level in a forage-finishing beef system without negative consequences on perceived beneficial fatty acids.