Effects of supplemental zinc concentration and source on performance, carcass characteristics, and serum values in finishing beef steers

Three studies were conducted to examine the effects of zinc concentration o r source in diets of finishing beef steers. In Exp. 1, 108 (British x Conti nental) beef steers were supplemented with concentrations of added zinc las ZnSO4) at 20, 100, or 200 mg/ kg of dietary DM. No differences (P > 0.10) were noted among treatments for ADG or gain:feed for the 112-d finishing pe riod. However, a linear (P < 0.10) decrease was noted in daily DMI with inc reasing zinc concentrations for the overall finishing period. No difference s (P > 0.10) were noted in hot carcass weight; dressing percentage; longiss imus muscle area; percentage of kidney, pelvic, and heart fat; or marbling score. There were, however, quadratic increases in s.c. fat thickness (P < 0.05) and yield grade (P < 0.01) with added zinc. In Exp. 2, 12 beef steers were used to examine effects of added dietary zinc on serum concentrations of cholesterol and fatty acid profiles. No differences (P > 0.10) were obs erved in cholesterol or fatty acids among the supplemental zinc levels. In Exp. 3, 84 Brangus- and Angus-sired steers were fed a steam-flaked corn-bas ed diet containing 30 mg of supplemental zinc per kilogram of dietary DM fr om one of the following sources: 1) ZnSO4, 2) Zn amino acid complex, or 3) a zinc polysaccharide complex. No differences (P > 0.10) were noted for the overall 126-d trial for ADG, DMI, or gain:feed ratio. Percentage kidney, p elvic, and heart fat was increased (P < 0.10) in steers supplemented with Z nSO4 vs the average of Zn amino acid and Zn polysaccharide complexes. Howev er, s.c. fat thickness was greater (P < 0.10) in steers supplemented with Z n amino acid and Zn polysaccharide complexes us ZnSO4. Serum zinc concentra tion did not differ (P > 0.10) among zinc sources. Supplemental zinc concen tration in finishing diets did not seem to influence feedlot performance an d had a minimal impact on carcass quality. Either the organic or inorganic source can be included in finishing diets without affecting feedlot perform ance.