Harmful effects of nicotinic acid occur at levels far in excess of requirements. Limited research has indicated that nicotinic acid and nicotinamide are toxic at dietary intakes greater than 350 mg per kg (160 mg per lb) of body weight per day (NRC, 1998). Nicotinic acid and niacinamide tolerance in swine has not been determined. Campbell and Combs (1991) fed up to 68 g niacin per kg feed to starting pigs and reported a significant decrease in feed intake and average daily gain in comparison with pigs fed diets containing 34 g niacin per kg feed.
