Effects of α-amylase supplementation on production performance, blood metabolites, nutrient digestibility, and rumen fermentation parameters of Holstein dairy cows in late lactation.

Current research on dairy cows primarily focuses on peak lactation, with limited exploration of late lactation. This study investigated the effects of α-amylase supplementation on production performance, blood metabolites, nutrient digestibility, and rumen fermentation in late-lactation Holstein cows. Thirty cows (average milk yield: 37.48 ± 1.63 kg; parity: 2.44 ± 0.70; lactation days: 210.17 ± 2.20) were randomly divided into two groups: the control group (CON) received a basal diet, while the experimental group (AM) was supplemented with 15 g/day α-amylase for 7 weeks (1-week adaptation + 6-week trial). Results showed that α-amylase significantly increased milk yield, energy-corrected milk (ECM), and milk protein yield ( < 0.01) and improved fat-corrected milk ( < 0.05). Milk protein content, total solids, and milk fat yield also tended to rise ( = 0.061, = 0.067, = 0.091, respectively). No significant differences were observed in dry matter intake (DMI), feed efficiency, or somatic cell count. Serum amylase concentration increased markedly in the AM group ( < 0.01), while other blood parameters remained unchanged. Starch digestibility improved significantly ( < 0.05), and neutral detergent fiber (NDF) digestibility showed a positive trend ( = 0.063). Rumen propionate concentration rose significantly ( < 0.05), with no major changes in pH, ammonia nitrogen, or acetate-to-propionate ratio. In conclusion, α-amylase supplementation in late lactation enhances nutrient digestibility, modulates rumen fermentation, and improves production performance, offering metabolic regulation potential for extending high productivity in late-stage lactation.