Effects of yeast-derived microbial protein on lactation performance and metabolic status of transition dairy cows

Abstract The objective of this study was to evaluate the effects of yeast-derived microbial protein (YMP) on performance and blood metabolites in transition cows. Twenty-four primiparous and multiparous Holstein cows were blocked according to expected calving date and parity, and randomly assigned to receive either a control (0 g YMP) or treated (YMP; 50 g YMP prepartum followed by 200 g YMP postpartum) pellet containing beet pulp and molasses. The study commenced 21 d prior to expected calving date and ended 28 d postpartum. Individual dry matter intake (DMI) and milk yields were recorded daily. Milk samples were collected twice weekly on two non-consecutive days and analyzed for fat, protein, lactose, somatic cell count and urea. Blood samples collected on d −21, −14, −7, −3, −1, 1, 3, 7, 14, 21 and 28 relative to calving were analyzed for metabolites, macrominerals and proteins. There was no effect of YMP treatment on DMI, milk yield and milk composition. However, YMP supplementation significantly reduced serum concentrations of non-esterified fatty acids from d 3 postpartum until the end of the study. Serum concentrations of β-hydroxybutyrate were also reduced in YMP-supplemented cows on d 3 and 7 postpartum. Moreover, YMP supplementation significantly increased serum glucose levels on d 3 and 7 postpartum, and reduced serum aspartate transaminase levels on d 14 and 21 postpartum. Overall, our results suggest that amino acid supplementation in the form of YMP may significantly reduce metabolic stress and fat mobilization from the adipose tissue in transition cows especially during the postpartum period without adversely affecting milk production.