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.
Highlights
Niacin and its vitamers nicotinamide (NAM) and nicotinic acid (NA) are important for the synthesis of the coenzymes NAD and NADP which are involved in a large number of biological pathways [1]
Excluding the CON group from data evaluation enabled a more powerful examination of the pooled variance caused by NA dose and galenic form, i.e., by evaluating the data according to a complete
It may be concluded that the experimental time of the present study was too short to induce differences in milk performance, NAM concentrations were moderately elevated. Another explanation is that present cows were in positive energy balance and as NA is able to balance enhanced lipid mobilization by the downregulation of lipolysis [13], it can be concluded that the absence of effects on milk production parameters is due to absent disturbances in energy metabolism. Both forms are readily available for ruminant’s metabolism and are able to substantially affect serum NAM concentrations indicating that the ruminal degradation of non-rumen protected (nRP) is not as massive as assumed formerly [4]
Summary
Niacin (vitamin B3) and its vitamers nicotinamide (NAM) and nicotinic acid (NA) are important for the synthesis of the coenzymes NAD and NADP which are involved in a large number of biological pathways [1]. The NRC [2] declared the requirement of niacin for a lactating cow with a body weight of 650 kg and 35 kg milk yield with 289 mg per day and it was shown that ruminants are capable of covering these requirements from different sources. Niacin and its vitamers have recently attracted increased interest as feed additives due to their promising targets for diverse effects on bovine metabolism. It was shown that feeding additional niacin as nicotinic acid (6–12 g niacin/d) influenced the ruminal ecosystem like the stimulation of the microbial protein synthesis [5], the increase of total protozoal counts [6,7] and the increase of butyric acid, valeric acid, propionic acid, and ammonia [5,6,7,8]. NA as feed additive was suggested to balance catabolic metabolism postpartum, because it was shown that NA is able to stimulate GPR109A receptor resulting in a down-regulation of the lipolysis via the dephosphorylation of the hormone-sensitive lipase in adipose tissue [13]
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