Effect of rumen-protected niacin on lipid metabolism, oxidative stress, and performance of transition dairy cows.

The objective of this study was to evaluate the effect of a rumen-protected niacin product (RPN; 65% nicotinic acid; NiaShure, Balchem Corp., New Hampton, NY) on lipid metabolism, oxidative stress, and performance of transition dairy cows. Thirty nonlactating multiparous Holstein cows in late gestation were paired according to expected calving date and randomly assigned to 12 g/ cow per day of RPN product or to an unsupplemented control (CON) diet. Treatment diets were fed from 21 d before expected calving through 21 d after parturition. Blood samples were taken on d -21, -14, -7, 1, 7, 14, and 21 relative to calving for plasma nonesterified fatty acid (NEFA), β-hydroxybutyrate (BHBA), glucose, and superoxide dismutase (SOD) analyses. Liver samples were taken by biopsy on d 1 and 21 relative to calving for triglyceride (TG) analysis. Data were analyzed for a randomized complete block design with repeated measures. Pre- and postpartum dry matter intake, milk yield, and protein were unaffected by treatment. Milk fat percentage (5.08 vs. 4.44%) and somatic cell score (3.93 vs. 2.48) were reduced for RPN. Treatment x time interactions were observed for energy-corrected milk (ECM) and fat-corrected milk (FCM) yields; RPN reduced ECM and FCM yields by 8.5 and 8.9 kg/ cow per day, respectively, in the first week of lactation. Although body weight and condition score decreased during the experimental period, no differences due to treatment were observed. However, calculated postpartum energy balance tended to be improved for RPN because of the reduction in ECM yield. Time and treatment x time effects were observed for plasma NEFA. On d 1 postpartum, NEFA reached 1,138 ± 80 µEq/L for CON compared with 698 ± 80 µEq/L for RPN. Cows supplemented with RPN tended to have lower plasma NEFA concentrations than CON cows on d 7 and 14 postpartum. Plasma BHBA, glucose, and SOD and liver TG concentrations were unaffected by treatment. In conclusion, supplementation with 12 g/cow per day of the RPN product provided a bioavailable source of niacin that modified lipid metabolism but did not affect milk yield over the first 3 wk of lactation or oxidative stress of transition dairy cows. [ABSTRACT FROM AUTHOR]