Review: A Meta-Analysis of Lactation Responses to Supplemental Dietary Niacin in Dairy Cows

Abstract A meta-analysis of published data was conducted to examine the response of lactating dairy cows to supplemental dietary nicotinic acid ( NA ). The data set was developed from 27 studies published between 1980 and 1998 where lactation performance responses to targeted supplementation of 6 and 12 g/d NA were reported. Response variables evaluated were DMI, milk yield and composition, feed efficiency, and plasma beta-hydroxybutyric acid, non-esterified fatty acid, and glucose concentrations. No efficacy of 6 g/d dietary supplemental NA was found. Similarly, dietary supplementation with 12 g/d NA did not affect DMI, milk fat or protein percentages, or measured plasma metabolites. However, responses to dietary supplementation with 12 g/d NA were observed for 3.5% fatcorrected milk ( FCM ) yield, feed efficiency (when calculated with 3.5% FCM), and milk fat and protein yields. Yields of 3.5% FCM, milk fat, and milk protein were 0.5 kg/d (P=0.06), 25.8 g/d (P=0.01), and 17.4 g/d (P=0.08) higher, respectively, for NA-supplemented cows. Feed efficiency calculated with 3.5% FCM was 0.03 units higher (P=0.09). A Type I/Type II error economic analysis of the 3.5% FCM yield response showed frequencies of the observed response being greater than the break-even responses by 54 and 57% when NA costs were $0.01 and $0.005/g, respectively. Further research on transition cows and incidence of metabolic disorders, higher dosages of NA, and ruminally protected NA appears warranted.