Influence of Different Supplemental Niacin Levels on Intake, Digestibility and Rumen Fermentation of Dairy Cows: A Meta-analysis

Abstract Rumen microbes can synthesis niacin but at fewer amount. Niacin is occasionally supplemented into dairy cows' ration to improve their production performance especially during early lactation period. The present study was aimed to assess the effect of different supplemental niacin levels on intake, digestibility and rumen fermentation of dairy cows through a meta-analytical study. A database was constructed from published literatures reporting niacin supplementation on dairy cows. A total of 49 studies from 46 published articles were integrated into the database. Different niacin levels at various supplemental levels were specified, i.e. 0 to 24 mg; nutrient intake and rumen fermentation parameters were integrated as well. Data were analyzed by a mixed model methodology in which different studies were treated as random effects whereas niacin levels were treated as fixed effects. Significancy of an effect was stated when P<0.05. When a parameter showed 0.05<P<0.1, then the effect was considered to have a tendency to be significant. The results showed that different levels of niacin supplementation did not significantly influence nutrient intake, digestibility and rumen fermentation of dairy cows (P>0.05). It is concluded that supplementation of niacin has less effect in improving intake, digestibilty and rumen fermentation