| dc.description.abstract | Niacin is occasionally supplemented into dairy cows’ ration to improve their production performance especially during early lactation period. Such supplementation can be done either in the form of nicotinic acid (NA) or nicotinamide (NM). The present study is aimed to assess which form of niacin is most effective in relation to the performance of dairy cows through a meta-analytical study. A database was constructed from published literatures reporting niacin supplementation on dairy cows. A total of 61 studies from 49 published articles were integrated into the database. Different niacin forms, i.e. NA or NM, either unprotected or protected at various supplemental levels were specified. Nutrient intake, rumen fermentation parameters, blood profiles, milk production and milk composition were integrated as well. Data were analyzed by a mixed model methodology in which different studies were treated as random effects whereas niacin forms (control, NA, NM) 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. Results revealed that, in contrast to our expectation, NA or NM supplementation did not significantly improve 4% fat-corrected milk production (FCM) than that of control. Levels of β- hydroxybutiric acid (BHBA) in blood plasma for control, NA and NM were 116.9, 97.9 and 102.7 mmol/l, respectively. Effects of NA or NM supplementation were insignificant for rumen fermentation parameters (volatile fatty acids and ammonia) as well as for milk quality (milk protein, milk fat, solid non fat and total solid). | en |
