Meta-analysis to determine the effects of supplementation of niacin during the transition or lactation period on performance in dairy cows

= 61.7%) heterogeneity observed. Similarly, RPN supplementation during the lactation period led to linear increases in DMI and yields of milk, ECM, fat and lactose, with respective increases of 0.60, 1.10, 0.70, 0.06, and 0.05 kg/d when cows were supplemented with 4.7 g/d niacin. Across 12 treatment comparisons from 8 experiments, RPN-supplemented cows produced 0.96 kg/d more milk than CON cows (WMD = 0.96; 95% CI = 0.62-1.31), with no heterogeneity observed. Overall, feeding 9.1 g/d of niacin from RUPN or 4.7 g/d of niacin from RPN during the lactation period improved milk production without improving feed efficiency in dairy cows.