Four crossbred Holstein x Zebu steers fitted with ruminal and abomasal cannulas were randomly assigned to a 4 x 4 Latin square to evaluate the effects of feeding corn or sorghum silages with and without microbial inoculant on intake, ruminal metabolism, total and partial digestibility of nutrients, and digesta passage rate. Diets contained, dry matter (DM) basis, a forage to concentrate ratio of 63:37. No significant differences were observed on the intakes of DM, crude protein (CP), and total digestible nutrients, which averaged 6.61, 0.75 and 3.96 kg/day across diets, respectively. Total and ruminal apparent digestibilities of DM, CP and neutral detergente fiber (NDF) also were not affected by diets averaging 61.17 and 61.91, 61.43 and 13.21, and 52.13 and 92.96%, respectively. However, a dietary effect was observed for the intestinal digestibility of NDF; steers fed corn silage had greater intestinal digestibility of NDF (9.08%) than those fed sorghum silage (4.77%). Ruminal pH was not affected by diet and time of collection, with an overall mean of 5.58. Conversely, concentration of ruminal ammonia was affected by time of collection with estimated maximum values of 9.04, 10.82, 8.84, and 9.47 mg/100 mL for diets containing corn and sorghum silages with and without microbial inoculant, respectively. Estimated digesta passage rates of diets containing corn and sorghum silages with and without microbial inoculant were of 4.29, 5.05, 4.44, and 5.12 %/h, respectively.
crude protein; neutral detergent fiber; passage rate; pH; ruminal ammonia; total digestible nutrients
