Relative Bioavailability of Niacin Supplements for Dairy Cows: Effects of Rumen Protection and of Feed Processing

Abstract

The present study aimed to examine the effective systemic bioavailability of niacin— with particular focus on its galenic form—and feed processing. Experiment 1 was conducted with 35 dairy cows to investigate the effects of various doses of oral supplemented nicotinic acid (NA) either in differing galenic forms (non-rumen protected (nRP) vs. rumen protected form (RP)) on serum niacin concentrations. Experiment 2 was designed as a pharmacokinetic study examining the serum niacin kinetics over 24 h after giving a single oral bolus of 24 g nRP or RP NA admixed in either pelleted or ground concentrate. In both experiments, only the niacin vitamer nicotinamide (NAM) was detected. Results of experiment 1 showed that both galenic forms at a dose of 24 g/cow daily elevated NAM concentrations at the beginning of the experiment. Despite a daily supplementation, NAM concentrations decreased continuously towards the end of the experiment which was more steeply in nRP NA (p = 0.03). On experimental day 21, NAM concentrations were higher when feeding RP NA (p = 0.03) and the highest dose (24 g/day and cow) (p < 0.01). Results of experiment 2 indicated that nRP and RP were characterized by similar pharmacokinetic profiles resulting in similar areas under the curves as a net result of the kinetic counterbalancing alterations. Pelleting seemed not to influence the relative bioavailability.

Keywords

• dairy cow
• niacin
• bioavailability
• feed processing
• pharmacokinetic