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Ruminal fluid from two heifers (384 ± 2 kg) fed an 85% concentrate diet was used to determine effects of degree of processing and N source and level on in vitro DM disappearance (DMD), starch availability, pH changes, and NH3 concentrations of corn and sorghum. In Exp. 1, treatments (2 × 4 factorial) were unprocessed corn and sorghum (UP) and each grain steam-flaked to bulk densities (BD) of 0.38, 0.33, and 0.28 kg/L (C38, B33, A28, respectively). Treatments in Exp. 2 (2 × 2 × 3 factorial within grain type) were UP and A28 with 0, 10, or 20 mg of N/g provided by either urea (U) or casein hydrolysate (CH). Starch availability of both grains increased linearly (P 0.10) DMD of corn or sorghum beyond 4 h, but DMD increased linearly (P |
