Impact of α-amylase supplementation on energy balance and performance of high-yielding dairy cows on moderate starch feeding

In dairy cows, exogenous alpha-amylase is suggested to improve starch utilization and positively affect performance and health traits linked to energy balance and fertility. In a 1-year feeding experiment, 421 cows were orally supplemented with alpha-amylase (treatment: 12.5g/kg dry matter (DM) addition rate to a concentrated feed) or non-supplemented (control) on the basis of an adlibitum total mixed ration (TMR). Every cow was allocated to a high- (>= 32kg milk/day) or late-lactation group (<32kg milk/day), in which the TMR starch content was 220 +/- 20.8g/kg DM and 183 +/- 24.8g/kg DM, respectively. The energetic effect of alpha-amylase supplementation seemed to be exclusively related to the high-lactation stage (5-100days in milk) in primiparous cows, where the daily milk yield was 32 +/- 0.49 versus 31 +/- 0.50kg per cow in the treatment versus control group (P<0.05). The pluriparous cows did not benefit from the supplementation that way. In neither primiparous nor pluriparous cows, was the milk composition, the fat-to-proteinratio, the somatic cell score, the backfat thickness, serum total bilirubin, beta-hydroxybutyrate and the fertility found to be systematically affected by alpha-amylase supplementation.