Abstract: The objective of this study was to investigate the effects of rumen-protected nicotinic acid (RPN) and rumen-protected choline (RPC) on lactation performance and hepatic lipid metabolism of perinatal dairy cows, and to provide theoretical basis for alleviating fatty liver of dairy cows. Twenty-four healthy Chinese Holstein perinatal dairy cows with similar parity were randomly divided into 4 groups in a 2×2 factor experimental design with 6 cows in each group, including control group (CON, basal diet), RPN group (RPN, basal diet +18.4 g·d^-1 RPN), RPC group (RPC, basal diet +60 g·d^-1 RPC) and both RPN and RPC group (RPN×RPC, basic diet +18.4 g·d^-1 RPN +60 g·d^-1 RPC), respectively. The experiment was conducted from 14 d prenatal to 21 d postpartum. The weekly weight and milk production of the dairy cows after calving, and the birth weight of the calves were recorded. Blood was collected every week, milk was sampled at 14 and 21 d after delivery, liver biopsies were taken on 21 d relative to parturition. The results showed that the supplementation of RPN or RPC had no significant impact on the performance of dairy cows and calves, including dairy cows body weight, calves body weight, milk production and milk composition (P>0.05). Supplementation of RPN and RPC significantly increased the contents of nicotinic acid (NA), choline (CH) and the level of very low density lipoprotein (VLDL) in plasma (P<0.001). RPN group and RPN×RPC group significantly reduced triglycerides (TG) content in liver (P<0.05). In summary, supplementing RPN and RPC to the basic diet of perinatal dairy cows has no significant effect on production performance, whereas they can improve the liver and body health of perinatal dairy cows by increasing the content of VLDL in plasma and reduce lipid deposition in the liver.

Key words: rumen-protected nicotinic acid, rumen-protected choline, perinatal period, lipid metabolism, liver