محمد حسین مرادی

Effects of barley grain in comparison with corn on performance, ruminal fermentation characteristics, and blood metabolites of Holstein fattening bulls The present study was conducted to investigate the effects of grain source (barley vs. corn) on growth performance, blood parameters and ruminal fermentation in Holstein fattening bulls. For this purpose, eighteen growing Holstein bulls with an initial BW of 328.4 (Sd 17.7) were assigned to experimental diets in a completely randomized design. Treatments consisted of barley based and corn based diets (100 % barley or corn as the source of grain in the concentrate). All calves had ad libitum access to water and feed throughout the experiment. Results indicate that dry matter intake (DMI) tended (P = 0.06) to be greater in calves fed with 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). Furthermore, final body weight was not different between treatments. Blood metabolites including glucose, beta-hydroxy butyrate, albumin, total protein and urea nitrogen were not affected by treatments. The concentration of alanine amino transferase in blood serum was not different between treatments, but substituting barley with corn decreased aspartate amino transferase during 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, in general, demonstrate that corn grain could be a proper substitution for barley grain in Iranian fattening bull's diets with high concentrate level and finely ground grains.