Abstract
Low-protein diets are increasingly used in nursery pigs to reduce nitrogen excretion and control post-weaning diarrhea. Niacinamide, as a bioavailable form of niacin, improves protein metabolic regulation and nitrogen utilization via promoting energy metabolism, redox balance, and intestinal integrity. In addition, synergistic effects in enhancing anti-inflammation and protecting against environmental stress are reported by combining niacinamide and Zn. The levels of dietary niacinamide for optimal growth and intestinal health were determined in two experiments using nursery pigs fed a low-protein diet with and without the addition of 0.2% ZnO. The diets were supplemented with 0, 30, 130, 230, or 330 mg/kg niacinamide. In Exp. 1, niacinamide quadratically improved (p < 0.05) growth performance with optimal effects at 50 mg/kg, increased hemoglobin (HGB) and mean corpuscular volume, and decreased diarrhea occurrence (p < 0.05) at 140 mg/kg in the diet with ZnO. In Exp. 2, niacinamide improved feed efficiency (p < 0.05) peaked at 130 mg/kg, and serum HGB and immunoglobulin A (p < 0.05) peaked at 170 mg/kg while decreasing diarrhea occurrence (p < 0.05) by up to 315 mg/kg in the pigs with no ZnO. The level of niacinamide required for optimal growth and intestinal health was associated with Zn availability.