SUPPLEMENTARY TRACE MINERALS FOR THE FEEDLOT FINISHING OF BEEF STEERS

Abstract

Steers in the finishing phase before slaughter were fed barley-based diets without (0TM) or with (+TM) supplemental trace minerals. The +TM diets of Trials 1 and 2 contained supplemental Cu, Zn, Mn and Se; the +TM diet of Trial 2 also contained supplemental Fe in addition to the other four trace minerals. All diets contained supplemental Co and I. Groups of steers were: Trial 1, 18 Angus-Charolais-North Devon crossbreeds, known as Selkirks (Sel) plus 18 Simmental × Sel; Trial 2, 10 Angus × Sel plus 30 Simmental × Sel. Average daily gain (ADG) was higher (P < 0.05) while feed efficiency (feed/gain; F/G) was improved 6% (P > 0.05) for +TM steers of Trial 1. There were no differences (P > 0.05) for ADG or F/G of Trial 2 when the +TM diet contained supplemental Fe. Hot carcass weight was not influenced (P > 0.05) by treatment in either Trial. In both Trials there were higher (P < 0.05) liver Cu and liver Mn for +TM steers, and no difference (P > 0.05) for liver Zn. Liver Fe was lower (P < 0.05) for +TM steers of Trial 1, but with no difference (P > 0.05) for Trial 2. Supplemental trace minerals increased ADG, but did not modify hot carcass weight in Trial 1. Liver Cu and Mn were increased in response to supplemental Cu and Mn in both Trials. It was not advantageous to provide supplemental Fe in Trial 2 in order to counteract the effect of supplemental Cu upon liver Fe observed in Trial 1. Key words: Steers, finishing phase, copper, zinc, manganese, iron