Niacin supplementation should be considered for all classes of swine. Much of niacin contained in common feeds (plant sources) is in a bound form that is not available to animals. In formulating swine diets, therefore, niacin values for corn and other cereal grains and their by-product feeds should be disregarded. It is best to assume that these feeds provide no available niacin for the pig or chick (Cunha, 1982b). Kodicek et al. (1956) determined that nicotinic acid could be liberated by alkali treatment of maize. This approach was suggested to have practical applications for the production of cereals. The work by Kodicek et al. (1956) and their subsequent study (Kodicek et al., 1959) further confirmed that without treatment, the nicotinic acid in maize is bound and unavailable to pigs. Kodicek et al. (1959) determined that if maize was treated with 1% lime water and baked into tortillas, nicotinic acid-deficient pigs recovered from their deficiency. Kodicek et al. (1959) suggested, with regard to the beneficial effect of curing the nicotinic acid deficiency in these pigs, that release of nicotinic acid from an unavailable bound form was involved.
The pig 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 swine diets do not contain large excesses of tryptophan, particularly diets based on corn. Tryptophan concentrations in corn are not only low but largely unavailable. Therefore, one should ensure that swine diets are adequate in niacin, since it is inexpensive and it would be poor economics to satisfy niacin needs by the more expensive tryptophan (Cunha, 1982a).
The most critical time for supplementation is during early growth, when requirements are the highest. Niacin requirements, as recommended by the NRC (1998) for swine, may be insufficient. Supplementation of niacin for swine is important to provide a reasonable safety factor, and higher niacin levels are recommended when subclinical disease level, stress and high production rates are expected. Nutritionists must set niacin fortification objectives in relation to the type of diet, class of pigs, stress conditions present and other factors that may influence the need by swine for niacin supplementation.
Cunha (1982a) recommends two levels of niacin supplementation for each class of swine, an "average" level and a "high" level. The high level is to account for factors that increase niacin needs considerably. Increased swine requirements recommended by Cunha (1982b) are more than double (up to 44 mg per kg; 20 mg per lb of diet) those of the NRC (1998) for growing swine under more stressful conditions, with breeding and lactating animals needing a four fold increase (44 mg per kg; 20 mg per lb of diet).
In addition to the critical time of early growth, especially with early weaning and the use of prestarter feeds, gestation is a period of special supplemental vitamin needs. Gestation is critical especially when feed intake is restricted to 1.4 to 2 kg (3 to 4.5 lbs) of feed per sow daily. The low level of feed intake is used to keep sows from becoming fat. However, this diet requires a higher concentration of niacin (as well as other nutrients) to provide the sow with the total niacin it needs daily (Cunha, 1982a).
Commercially produced niacin is quite stable compared with most other vitamins. Niacin and niacinamide were found to be stable for three months in premixes with or without minerals (Verbeeck, 1975). Gadient (1986) reports niacin to be insensitive to heat, oxygen, moisture and light. As a general rule, the retention of niacin activity in pelleted feeds after three months at room temperature is 95% to 100%.