Comparison of barley and corn grain on performance, ruminal fermentation, and blood parameters in Holstein fattening bulls

The present study was conducted to investigate the effects of grain sources on growth performance, blood parameters and ruminal fermentation in Holstein fattening bulls. For this purpose, eighteen growing Holstein bulls (245 ± 11 d) with an initial BW of 328.4±17.7 were assigned to experimental diets in a completely randomized design. Treatments consisted of barley or corn based diets (100 % barley or corn as the source of grain). Results indicated that dry matter intake (DMI) tended (P = 0.06) to be greater in calves fed corn than those fed barley. Calves fed with corn grain had greater average daily gain (ADG) than those received barley during the first period (d 1 to 28); however, treatments had no effect on ADG in the second period (d 29 to 56). Blood metabolites including glucose, beta-hydroxy butyrate, albumin, total protein and urea nitrogen were not affected by treatments, however, substituting barley with corn decreased aspartate amino transferase in both periods (P = 0.01 and P = 0.05, respectively). Ruminal pH and total volatile fatty acids concentrations were similar between treatments, however, in calves fed with corn grain the molar proportion of acetate (P = 0.03) and acetate to propionate ratio (P = 0.04) increased and the molar proportion of propionate decreased in comparison with calves fed barley. These results, demonstrated that corn grain could be a promising substitution for barley grain in fattening bull's diets with high concentrate level and finely ground grains.