Effect of niacin supplementation on rumen fermentation characteristics and nutrient flow at the duodenum in lactating dairy cows fed a diet with a negative rumen nitrogen balance

Abstract

The aim of the present experiment was to ascertain if a daily niacin supplementation of 6 g/cow to lactating dairy cow diets can compensate for the decrease in rumen microbial fermentation due to a negative rumen nitrogen balance (RNB). A total of nine ruminally and duodenally fistulated lactating multiparous German Holstein cows was used. The diets consisted of 10 kg dry matter (DM) maize silage and 7 kg DM concentrate and differed as follows: (i) Diet RNB- (n = 6) with energy and utilisable crude protein (CP) at the duodenum (uCP) according to the average requirement of the animals, but with a negative RNB (-0.41 g N/MJ metabolisable energy [ME]); (ii) Diet RNB0 (n = 7) with energy, uCP, and RNB (0.08 g N/MJ ME) according to the average requirement of the animals; and (iii) Diet NA (nicotinic acid; n = 5), which was the same diet as RNB-, but supplemented with 6 g niacin/d. The negative RNB affected the rumen fermentation pattern and reduced ammonia content in rumen fluid and the daily duodenal flows of microbial CP (MP) and uCP. Niacin supplementation increased the apparent ruminal digestibility of neutral detergent fibre. The efficiency of microbial protein synthesis per unit of rumen degradable CP was higher, whereby the amount of MP reaching the duodenum was unaffected by niacin supplementation. The number of protozoa in rumen fluid was higher in NA treatment. The results indicated a more efficient use of rumen degradable N due to changes in the microbial population in the rumen when niacin was supplemented to diets deficient in RNB for lactating dairy cows.

Effects of nitrogen underfeeding and energy source on nitrogen ruminal metabolism, digestion, and nitrogen partitioning in dairy cows1

“…The EMPS was unaffected by the N level. Similarly, no variation in EMPS when decreasing the dietary level of degradable N up to 11% CP was reported by Peyraud et al (1997) in dairy cows and by Valkeners et al (2008) in bulls, and a nonsignifi cant trend for a decrease in EMPS has been found by Aschemann et al (2012b). More generally, among ruminants, EMPS does not appear to be closely related to dietary CP level, but rather to rumen protein balance as well as to TOMDR and passage rates (Sauvant and Nozière, 2011), as also observed in the present study, where rumen protein balance increased and EMPS decreased between high-starch and high-fi ber diets at a similar CP level.…”

Postruminal synthesis modifies the odd- and branched-chain fatty acid profile from the duodenum to milk

“…The 2 experiments from which samples were obtained were explained in detail by (Fanchone et al, 2013) and (Aschemann et al, 2012). Brief descriptions of those experiments are given below.…”

“…Assuming duodenal 15:0 and 17:0 are completely secreted in milk, de novo synthesis of linear odd-chain FA accounts for, on average, 0.344 ± 0.134 (g/g, experiment 1) and 0.374 ± 0.160 (g/g, experiment 2) of the linear odd-chain FA secreted in milk. Obviously, recovery of duodenal FA in milk is most likely less than 1, due to incomplete duodenal absorption, oxidation, or incorporation in body tissues, which means that the contribution of de 1 RNB = ruminal nitrogen balance, with RNB− = balanced diet in terms of ME and utilizable CP at the duodenum according to the average requirements of the dairy cows in experiment 2, but with a shortage of rumen degradable protein (RNB = −0.41 g of N/MJ of ME); RNB-NA = diet with the same composition as RNB− but to which 6 g/d of niacin was added; RNB0 = diet with the same composition as RNB− but to which urea was added to balance rumen degradable N supply (RNB = 0.08 g of N/MJ of ME; Aschemann et al, 2012). 2 The source effect (S) refers to the difference between duodenum and milk.…”

“…Consequently, samples for the current study were obtained from 2 dairy cattle experiments initially designed to evaluate the effect of diet composition on efficiency of N utilization, and where large variation in duodenal flow of microbial protein (Fanchone et al, 2013;Aschemann et al, 2012), rumen proportions of VFA (Fanchone et al, 2013;Aschemann et al, 2012), and the rumen microbial population (Belanche et al, 2012) were measured. The dietary effect on both DMI, milk production and composition, and duodenal flow of microbial N were reported previously (Aschemann et al, 2012;Fanchone et al, 2013).…”

Niacin nutrition and rumen-protected niacin supplementation in dairy cows: an updated review

“…Thus, the free niacin supplementation may improve the growth for ruminal protozoa in the rumen and increase the protozoal predation of bacteria (33) . Aschemann et al (30) proposed that the free niacin supplementation might change the composition of microbial protein by increasing the protozoal protein and decreasing the bacterial protein, which could be the reason for the unchanged microbial protein content reaching the duodenum. In addition, those authors suggested the reduced faecal N excretion in niacin supplemented animals could also be related to the increased protozoal protein because the digestibility of protozoal protein is greater than bacterial protein (34) .…”