The use of niacin for Danish dairy cows has recently received increased interest in the dairy industry. This interest is based on an expectation that niacin will increase milk yield and/or prevent ketosis. In ruminants, niacin (vitamin B3) is synthesised by the microflora in the rumen. It has been questioned whether the synthesis of niacin in the rumen is adequate in order to secure an optimal production and health in dairy cows in early lactation. The objective of this report wasis to review the effects of niacin on the fermentation pattern in the rumen, blood and liver parameters, feed intake and performance to determine if niacin is able to improve the negative energy balance and prevent ketosis in early lactating dairy cows.
Results and discussion
Feeding 6–12 g of niacin/cow/day does not change the fermentation pattern, the total concentration of volatile fatty acids, or the pH in the rumen. Feeding 6–12 g of niacin/cow/day in early lactation increases the concentration of niacin in plasma, thus, increasing the supply to the cow. The increased supply of niacin does not significantly affect plasma concentrations of glucose and NEFA (Figure 1). This indicatinges that supplementary niacin does not reduce the mobilisation of adipose tissue, and consequently does not improve the negative energy balance. However, there is a tendency that supplementary niacin decreases the plasma concentration of b-hydroxybutyrate (BHB), thus acting antiketogenically (Figure 1). Supplementary niacin does not affect the content of TAG or lipid in the liver. Feeding 6–12 g of niacin/cow/day does not affect feed intake, milk yield or fat and protein content of the milk (Figure 2). Furthermore, niacin supplementation is not able to prevent the drop in the protein content of the milk, which is typically seen when allocating supplementary fat in a feed ration. Only one study has investigated the effect of niacin supplementation on the incidence of ketosis, and reported a tendency towards a lower incidence when feeding 6 g of niacin/cow/day.
Figure 1. The effect of niacin on plasma concentrations of NEFA, BHB and glucose in early lactating dairy cows shown as percentage of control group (based on 10 references).
Figure 2. The effect of niacin on milk yield and milk composition in early lactating dairy cows shown as percentage of control group (based on 8 references).
Supplementary niacin does not reduce the mobilisation of adipose tissue or the content of lipid in the liver. It is therefore unlikely that niacin can prevent fatty liver and ketosis. Furthermore, niacin does not affect feed intake, milk yield or milk composition in early lactating dairy cows.