Effect of high-concentrate diets on in situ dry matter disappearance, digestibility, digesta kinetics, ruminal fermentation and ruminal development in calve

Two steer trials evaluated effects of high concentrate diets on in situ DM disappearance, ruminal fermentation, digesta kinetics and ruminal development. In trial 1, four ruminally cannulated steers were used in a 4 x 4 Latin square design. Treatments were steam flaked or ground corn, barley, wheat and sorghum with and without the addition of a grain conditioner. In trial 2, 16 Holstein calves (avg initial birth weight 56 kg) were used in a completely randomized design (four/treatment) repeated over five periods. Treatments were steam flaked corn, sorghum, barley and oats.;In trial 1, in situ DM disappearance (DMD) was greater (P $<$.05) for ground sorghum, wheat and barley at 0, 24 and 24 h, respectively, than for steam flaked grain. Steam flaking increased (P $<$.10) in situ DMD at 36 h with corn or sorghum and at 48 h with steam flaked sorghum compared with ground grain.;In trial 2, no differences among treatments were observed for feed intake, daily gain or feed/gain ratio. Ruminal pH was greater (P $<$.10) in calves receiving an oat based diet. Ammonia nitrogen concentrations were greater (P $<$.10) in calves receiving corn in period 1 and corn or barley in periods 2 through 4 compared with other grains. Ruminal acetate, butyrate, isovalerate and isobutyrate proportions were greater (P $<$.10) in calves receiving oats compared with calves receiving corn, barley or sorghum. Ruminal propionate and valerate proportions were greater (P $<$.10) in calves receiving a barley diet than for other grains throughout the five periods. Ruminal fluid kinetics among all four diets revealed a trend of increasing with time through period 3 then declining in periods 4 and 5. Growth of ruminal papillae increased with age; however, papillae from calves receiving oats were decreased in length and width during periods 2, 3, 4 (P $<$.05) and 5 (P $<$.10) when compared with calves receiving corn, sorghum or barley. Gross histology of ruminal papillae indicated calves receiving corn or barley had more active layers of epithelial tissue compared with calves receiving sorghum or oats. (Abstract shortened with permission of author.).