Performance of Lactating Dairy Cows Fed Complete Pelleted Diets Based on Wheat Straw, Barley and Wheat

Lactation performance, serum glucose, free amino acids, insulin and non-esterified fatty acids (NEFA) concentrations were measured in dairy cows to evaluate three complete pelleted diets. Digestion coefficients were obtained with steers. The diets contained 17.5, 32.5 and 47.5% wheat straw, (designated LS, MS and HS, respectively). Overall health remained satisfactory. Energy digestibility increased from 64.0% on LS, to 69.6% on MS, and to 76.2% on LS. Fat-corrected milk yield and solids-corrected milk yield tended to be lower on LS, whereas total milk solids, percent milk fat and grams of milk fat yield were lower on LS than on MS and HS. Milk protein and solids-not-fat percentages were elevated on the LS diet. Little variation was observed in serum amino acid concentrations. A significant (P < 0.005) negative correlation (−0.52) was observed between milk fat percent and serum insulin.