RESUMO
Thirty multiparous lactating Holstein cows with an average live body weight of 642 ± 21 kg and an average daily milk yield of 30.46 ± 0.59 kg were used in this study. Cows with parities of 2 and 4 were used following their peak period, and were divided into three groups, with ten cows in each group. The control group was fed yellow corn grain rations (YCG), while for the 2nd and 3rd groups, 25 and 50% of YCG was replaced with dry sugar beet pulp (DSBP), denoted as DSBP25 and DSBP50, respectively. The contents of dry matter, organic matter, ether extract, nitrogen-free extract, and fiber carbohydrate in the experimental rations tended to decrease; however, crude protein, crude fiber, ash, and fiber fractions tended to increase in the DSBP25 and DSBP50 groups. Only crude fiber digestibility increased (p < 0.05) in the DSBP rations. Rumen pH value and concentration of ammonia nitrogen (NH3-N) decreased, while the concentration of total volatile fatty acids (TVFAs) increased in the DSBP25 and DSBP50 groups. The concentrations of total protein and globulin in blood plasma were higher (p < 0.05) in DSBP25 and DSBP50 than in YCG. However, plasma albumin concentration, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) activities were lower (p < 0.05) in DSBP50 than in YCG. Milk yield and yield of 4% fat-corrected milk (4% FCM) were higher (p < 0.05) in DSBP25 and DSBP50 than in YCG. Fat, protein, solids not fat (SNF), and total solids (TS) contents in milk increased significantly (p < 0.05) for feeding rations containing DSBP. Feed cost was reduced, but the output of milk yield increased with DSBP. In conclusion, introducing DSBP into the rations of Holstein dairy cows led to significant improvements in their productive performance.