The objective of this study was the evaluation of the effects of grain processing (steam-rolled vs. steam-flaked) and monensin on ruminal parameters. Sixteen Holstein calves were ruminally canulated with 3 to 5 days of life, and utilized on a completely randomized design block with a 2 x 2 factorial arrangement. The animals received concentrate ad libitum up to 2 kg/d, plus 4 L/d of milk. Calves had free access to water. After weaning at the eight weeks of life, calves received concentrate and chopped hay. Animal performance, concentrate and hay intakes were lower than expected and not affected by treatments. The molar proportion of propionate was higher for steam-rolled concentrate. There was a tendency for higher total VFA (P = .11) and butyrate (P = .13) for steam-rolled corn. Monensin tended to reduce ruminal N-NH3 concentration (P = .12). Weight of reticulum-rumen (as % total tract) tended (P = .09) to be higher for calves on steam-rolled and monensin concentration. However, the capacity of reticulum-rumen was increased by steam-rolled and monensin feeding. Steam-flaked concentrate resulted on heavier abomasum, as % total tract.
ionophore; ruminal ammonia; volatile fatty acids
