Niacin supplementation must be considered as a possibility with all classes of animals and in particular with poultry diets. Much of niacin in common feeds (plant sources) are in a bound form that is not available to animals. In formulating poultry diets, therefore, niacin values for corn and other cereal grains and their by-product feeds should be largely disregarded. It is best to assume that these feeds provide no available niacin for the chick or pig (Cunha, 1982). The chick and most species can use the essential amino acid tryptophan to synthesize niacin, but they cannot convert niacin back to tryptophan. Therefore, if a diet contains enough niacin, the tryptophan is not depleted for niacin synthesis. Most poultry diets do not contain large excesses of tryptophan, particularly diets based on corn. Tryptophan concentrations are not only low in corn, but largely unavailable. Therefore, one should ensure that poultry diets are adequate in niacin since, as it is inexpensive, it would be poor economics to satisfy niacin needs by the more expensive tryptophan (Cunha, 1982).
The most critical time for supplementation is during early growth when requirements are the highest. Niacin requirements as recommended by NRC (1994) for poultry may be insufficient. Supplementation of niacin for poultry is important to provide a reasonable safety factor and higher niacin levels are recommended when subclinical disease, stress and higher production rates are expected. Nutritionists must judge their own operation in relation to the type of diet, strain of birds, stress conditions present and other factors which may influence the need by poultry for niacin supplementation. Maurice (1988) reported that, for fast-growing modern turkeys, niacin supplementation of 140 mg per kg (63 mg per lb) of diet in young poults and 50 to 100 mg (23 to 45 mg per lb) for older birds is needed to address the unpredictable and variable factors encountered under commercial production.
Niacin is supplied in two forms, niacinamide and nicotinic acid, with both forms providing available niacin. In studies with chicks, relative to nicotinic acid used as a standard (100%), nicotinamide activity was 124%. Nicotinamide in nicotinamide adenine dinucleotide (NAD) was utilized with an efficiency of 95% relative to nicotinamide per se (Oduho and Baker, 1993). Crystalline products are used in feeds and pharmaceuticals, and dry dilutions are used in feeds. An additional source of supplemental niacin would be from the vitamin K supplement menadione nicotinamide bisulfite (MNB). Results with chicks suggest that MNB is fully effective as a source of vitamin K and niacin activity (Oduho et al., 1993).
Commercially produced niacin is quite stable compared to most other vitamins. Synthetic niacin and the amide were found to be stable in premixes with or without minerals for three months (Verbeeck, 1975). Gadient (1986) reports niacin to be insensitive to heat, oxygen, moisture and light. The retention of niacin activity in pelleted feeds after three months at room temperature should be 95% to 100% as a general rule.
