Effect of niacin supplementation on digestibility, nitrogen utilisation and milk and blood variables in lactating dairy cows fed a diet with a negative rumen nitrogen balance

Abstract

The aim of the present experiment was to determine if a niacin supplementation of 6 g/d to lactating dairy cow diets can compensate negative effects of a rumen nitrogen balance (RNB) deficit. A total of nine ruminally and duodenally fistulated lactating multiparous German Holstein cows were successively assigned to one of three diets consisting of 10 kg maize silage (dry matter [DM] basis) and 7 kg DM concentrate: Diet RNB- (n = 6) with energy and utilisable crude protein 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]); Diet RNB0 (n = 7) with energy, uCP and a RNB (0.08 g N/MJ ME) according to the average requirement of the animals and, finally, Diet NA (n = 5), which was the same diet as RNB-, but supplemented with 6 g niacin/d. Samples of milk were taken on two consecutive days, blood samples were taken on one day pre- and post-feeding and faeces and urine were collected completely over five consecutive days. The negative RNB reduced milk and blood urea content and apparent total tract digestibility of DM, organic matter (OM) and neutral detergent fibre (NDF). Also N excretion with urine, the total N excreted with urine and faeces and the N balance were reduced when the RNB was negative. Supplementation of niacin elevated plasma glucose concentration after feeding and the N balance increased. Supplementing the diet with a negative RNB with niacin led to a more efficient use of dietary N thereby avoiding the negative effects of the negative RNB on the digestibility of DM, OM and NDF.

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

“…The proportion of protozoal protein might have increased and overcompensated for the expected decrease in the amount of bacterial protein. This assumption of an increasing flow of protozoal protein to the duodenum was in line with other results from the same trial (Aschemann et al 2012) as the faecal N excretion was reduced in the niacin supplemented animals. It is known that the digestibility of protozoal protein ranged between 87 and 91%, while bacterial protein had lower digestibilities between 74 and 79% (Owens and Zinn 1988).…”

“…Table 2 shows the mean values of the chemical composition of the silage and the diets. The calculated energy content varied slightly between the diets due to differences in measured digestibilities (Aschemann et al 2012). The analysed CP content was 15.6% for the balanced Diet RNB0 and 12.2% for Diets RNB-and NA.…”

“…In Period 2, two cows were assigned to Diets RNB0 and RNB-, respectively, and one animal to Diet NA. In Period 3, three cows received Diet RNB0 and two cows were fed Diets RNB-and NA, respectively (Aschemann et al 2012). No cow received the same treatment twice.…”

“…As reviewed by Niehoff et al (2009), studies concerning the effect of dietary niacin on rumen metabolism provide inconsistent results. Nevertheless, in several studies supplemental niacin improved MP synthesis in the rumen of buffaloes and dairy cows (Riddell et al 1980;Kumar and Dass 2005;Niehoff 2009) and the efficiency of use of dietary N and the N balance (Aschemann et al 2012). These effects might be attributed to protozoa which are not able to synthesise niacin and thus benefit in particular from additional niacin in the diet .…”

Effect of Complete Feed Silage Made from Agricultural Waste on Milk Yield and Quality of Dairy Cows

“…This might be attributed to the low the dietary CP in EG-RB treatment compared with another treatment (Table 1-4). According to Aschemann et al (2012) that the dietary CP as low as 12% depressed nutrient digestibility and microbial protein synthesis in the rumen. The DMI and milk production were decreased when feeding of metabolizable protein deficient diets (Lee et al, 2011;2012a).…”