Digestibility and performance of dairy bulls fed corn and grass silages with various sequences and levels of barley

Abstract

Sixty Canadian Holstein male calves (mean weight 261 kg), previously fed all-concentrate diets, were allocated to one of six different sequences of barley supplementation. Rolled barley was provided in the diet at three levels (0, 17 and 34% on a DM basis) with either grass or corn silages, and fed as a total mixed ration for 91, 77 and 70 d during periods 1,2, and 3, respectively, to ensure consumption of 330 kg of barley per animal for the entire experiment. Barley supplementation in the last period improved average daily gain over the whole experiment by 0.223 kg d−1 (P = 0.0154), and feed efficiency by 55% (P = 0.0062) compared to inclusion of barley in the silage mixtures during the first period. Feed efficiency improved with concentrate supplementation of both silages (P ≤ 0.0001), but the improvement with grass silage was greater than with corn silage (P = 0.0041). Dry matter and energy digestibilities were not affected by feed sequences (P = 0.1025, P = 0.0833, respectively), but they were higher for mixed diets than for pure silage (P = 0.0186, P = 0.0218, respectively). Dry matter intake was 0.81 kg d−1 higher (P ≤ 0.0001) when concentrate was added to the diet. These results suggest that energy feeds such as barley are more efficiently used in the last part of growth. This experiment demonstrates the feasibility of switching grain-fed calves to roughage diets. Key words: Barley, dairy bulls, energy distribution, corn silage, grass silage