Interaction effect of starter physical form and alfalfa hay on growth performance, ruminal fermentation, and blood metabolites in Holstein calves

The present study was conducted to evaluate the effects of physical form of starter and alfalfa hay (AH) provision on growth performance, ruminal fermentation, and blood metabolites of Holstein dairy calves. Forty-four 3d-old Holstein dairy calves with a mean starting BW of 39.9 ± 1.1 kg were used in a 2 × 2 factorial arrangement. The factors were dietary forage level (0 or 150 g kg-1 AH; DM basis) and physical form of starter feed (coarsely mashed vs. pelleted). Individually housed calves were randomly assigned to 4 treatments: 1) a coarsely mashed starter feed without AH provision (MS-NAH), 2) a coarsely mashed starter feed with AH provision (MS-AH), 3) a pelleted starter feed without AH provision (PS-NAH), and 4) a pelleted starter feed with AH provision (PS-AH). The calves were weaned on d 60 and remained in the study until d 70. The results showed that feeding pelleted starter decreased starter intake significantly compared with coarsely mashed groups during the post-weaning (P < 0.01) and the entire period (P = 0.026).The interaction between AH inclusion and physical form of starter feed tended to be significant for both average daily gain (P = 0.092) and feed efficiency (P = 0.086). Inclusion of AH in the starter feeds increased rumination time and body barrel in calves. Blood urea nitrogen concentration in calves fed AH increased during post-weaning stage. Blood aspartate aminotransferase concentration was greater in calves fed PS form than those fed MS form. Although AH inclusion prevented rumen pH reduction during the pre-weaning period in calves fed PS form; ruminal pH decreased in PS groups in comparison with coarsely mashed groups during the post-weaning period. The pelleted form of starter increased total short chain fatty acids and butyric acid concentrations. However, coarsely mashed form and AH supplementation increased acetate concentration in the ruminal fluid. Overall, the results indicated that coarsely mashed form of starter could be recommended for Holstein dairy calves. Furthermore, AH inclusion in the starter diet may ameliorate the negative effects when pelleted starter is fed to dairy calves.