Niacin (vitamin B3) is an indispensable building block for the nicotinamide component of important coenzymes. NAD and NADP. These, in turn, are essential for energy management in ruminants. NAP and NADP play a role in carbohydrate metabolism (glycolysis and citric acid cycle), fat metabolism (synthesis and degradation of glycerol and fatty acids, and synthesis of steroids) and protein metabolism (synthesis and breakdown of amino acids). In ruminants, niacin supports the liver in converting ammonia into urea, and in handling ketone bodies. Last but not least, rumen microbes also consume niacin during metabolism, which results in increased microbial protein production and increased propionic acid formation.
Ruminants can cover their niacin requirements in three ways. First, by converting tryptophan into niacin in the body. The efficiency of this conversion is very low, however. In addition, vitamin B2, vitamin B6 and iron are also needed for this conversion. It is also dependent on the animal's protein and energy supply. Especially in the transition phase, the formation of niacin in this way is very slow.
In addition to the conversion mentioned above, niacin is also formed in the rumen. Santschi et al. (2005) demonstrate that the apparent synthesis of niacin in the rumen is about 2g/day. Recent research by Seck et al. (2017) shows that the production of niacin in the rumen decreases with a higher proportion of roughage in the rations. There is of course an optimum here. If the rumen does not function properly, as a result of rumen acidosis for example, the production of niacin can be reduced all the way to zero.
Finally, cows can get niacin from their rations. Its availability very much depends on the raw material, however. Only a very small amount of niacin can be obtained from grains. In addition, a large part of this is used by the microbes in the rumen. To prevent this, additional rumen-resistant niacin should be supplemented. Nonetheless, it appears that administering a higher dosage of variable niacin to cows at the start of lactation has a positive effect on milk production, milk protein, and NEFAs in the blood.
Increased administration of niacin is therefore especially desirable during the transition period and at the start of lactation. Extra niacin also has a positive effect, however, on growth in beef cattle and lambs. Variable niacin should be given in higher dosages than resistant niacin. Twilmij can supply both standard niacin (variable) and resistant niacin. For further details on the application of this vitamin, please contact your account manager or Elwin Brons, our ruminant nutritionist: firstname.lastname@example.org