Performance, carcass characteristics, and ruminal pH of Nellore and Angus young bulls fed a whole shelled corn diet

Abstract

The objectives of this study were to test the interaction of breed (Nellore or Angus) and diet (whole shelled corn [WSC] or ground corn [GC] with silage) on growth performance, carcass characteristics, and ruminal pH of young bulls. Thirty-six bulls (18 Nellore and 18 Angus) with the range in age of 18 to 22 mo and BW of 381 ± 12 kg were used in a completely randomized design experiment with a 2 × 2 factorial arrangement of treatments (2 breeds and 2 diets). Experimental diets (DM basis) included 1) a GC diet containing 30% corn silage and 70% GC- and soybean meal–based concentrate and 2) a WSC diet containing 85% WSC and 15% of a soybean meal– and mineral-based pelleted supplement. An additional 8 bulls were slaughtered at the beginning of the experimental period for determination of initial carcass weight. The treatments were Nellore fed the GC diet, Nellore fed the WSC diet, Angus fed the GC diet, and Angus fed the WSC diet. Greater DMI (P < 0.01), ADG (P < 0.01), and G:F (P < 0.01) were observed in Angus bulls compared with Nellore bulls, regardless of diet. Lower average ruminal pH (P = 0.04), maximum ruminal pH (P = 0.02), and DMI (P < 0.01) were observed in bulls fed the WSC diet than in those fed the GC diet. In addition, bulls fed the WSC diet had greater G:F (P < 0.01). The WSC diet led to greater variation in DMI compared with the GC diet (P < 0.01). Omasum and large intestine percentage was affected by diets only in the Angus breed (P < 0.02) and were greater when bulls were fed the GC diet. The WSC diet without forage may be useful for feedlots because this diet promoted greater G:F than the GC diet, regardless of breed. However, special care must be exercised in feed management during adaptation and throughout the feeding of Nellore animals to avoid digestive disorders and fluctuations in DMI.