SORGHUM GRAIN PROCESSING AND BUFFER ADDITION FOR EARLY LACTATION COWS

Thirty-six early lactation cows (51 DIM) were used in an 8-wk trial (3 x 2 factorial) to compare sorghum grain processed by dry rolling or steam flaking to .40 or .27 kg/L bulk density in TMR with or without 1% buffer (sodium sesquicarbonate). Mixed diets (16% CP) contained 42% sorghum grain with alfalfa hay as the forage source. When grain was steam flaked to .40 kg/L (31 lb/bu), milk yield was increased, and efficiency was improved, without decreasing intake or milk fat percentage. Further processing of the grain to a flake density of .27 kg/L (21 lb/bu) depressed intake and milk fat percentage, and inclusion of buffer in the diet did not alleviate these problems. Steam flaking sorghum grain increased DM, OM, starch, and CP digestibilities; lowered ruminal ammonia and acetate to propionate ratio; and increased fecal pH. The sodium sesquicarbonate buffer did not influence diet digestibility, milk fat percentage, or ruminal pH, but it increased acetate to propionate ratio in ruminal fluid. Cows fed the buffered diets consumed less feed, which resulted in increased gross efficiency. Compared with dry rolling, steam flaking the sorghum grain to .40 kg/L improved performance, but the lowest flake density was detrimental, and effects were not alleviated by inclusion of 1% buffer in the diet.