Response of large and medium frame beef steers to protein and zinc supplementation of a corn silage-corn finishing diet
Pond, W.G. | Oltjen, R.R.
Three hundred twenty crossbred steers were used to determine the effect of supplementary protein (0 vs 3%) and zinc (0 vs 36 ppm) in a 2 x 2 x 2 factorial arrangement of treatments on the weight gain, feed consumption and gain:feed ratio of large-frame and medium-frame size cattle full fed a corn silage-corn finishing diet. The experiment was conducted in two replicates (January-June and July-December) of 160 steers each, composed of 80 large-frame (Gelbvieh x Simmental x Hereford x Angus) and 80 medium-frame (Pinzgauer x Red Poll x Angus x Hereford) steers kept in concrete-slotted floor pens (four pens of five steers of each frame size per diet in each replicate). Daily gain and gain:feed ratio were greater in large-frame than in medium-frame cattle. Steers fed the 13% protein diet had higher adjusted final weight (P less than .05) and daily gain (P less than .05) than steers fed the 10% protein diet. There was no effect of dietary Zn level and no interactions between protein and Zn, protein and frame size or Zn and frame size for any criterion of response. It is concluded that a basal level of 24 ppm Zn in the diet is adequate for maximum daily gain and gain:feed ratio of steers fed corn-corn silage finishing diets from 300 kg body weight to slaughter at approximately 550 kg. The higher adjusted final weight and greater daily gain of steers fed the high protein diet suggests that corn silage-corn diets containing 10% protein may need to be supplemented with protein for steers weighing 330 to 350 kg initially and fed the diet ad libitum. There was no evidence for a higher requirement of either dietary protein or Zn in large-frame than in medium-frame finishing cattle.
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