PSVII-20 Functional requirement of nicotinamide for growth performance, blood profiles, and gut health of finishing pigs.

Abstract The growing use of low-protein diets in the swine industry may reduce the natural intake of nicotinic acid from traditional feed sources such as soybean meal. This could potentially compromise the health and growth performance of pigs. Nicotinamide supplementation could therefore play a critical role in meeting metabolic demands. This study aimed to investigate the functional requirements of nicotinamide in finishing pigs fed low-protein diets, focusing on blood parameters, intestinal health, and growth performance. Sixty-four pigs (80 ± 0.13 kg body weight) were randomly assigned to four dietary treatments supplemented with 30 (NAM30), 130 (NAM130), 230 (NAM230), and 330 (NAM330) mg/kg nicotinamide for 30 days. Each treatment had four replicate pens and four pigs per pen. Parameters assessed included growth performance, serum physiology and biochemistry, oxidative stress markers, immune indicators, rectal volatile fatty acids (VFAs), and rectal microbiota. Data was analyzed using SAS 9.4 (Cary, NC, USA), and polynomial contrasts were used to assess linear and quadratic effects of increasing niacinamide levels. A contrast was used to compare the NAM30 and NAM130 groups. The NAM130 group showed higher (P < 0.05) hemoglobin levels compared with the NAM30 group. Serum alanine aminotransferase (ALT) levels increased both linearly and quadratically (P < 0.05), with the highest response observed at 221 mg/kg, suggesting a threshold for potential physiological effects. The NAM130 group showed lower serum malondialdehyde (MDA) levels (P < 0.05) compared with NAM230, while glutathione peroxidase (GSH-Px) levels tended to increase linearly (P = 0.066). Serum interleukin-1β (IL-1β) levels decreased (P < 0.05) in the NAM130 group compared to NAM230 and showed a linear increase (P < 0.05) with higher nicotinamide supplementation. Furthermore, the NAM130 group reduced (P < 0.05) the abundance of Streptococcus and the Simpson diversity index compared with the NAM30 group. No significant differences were observed in average daily gain (ADG), average daily feed intake (ADFI), or gain-to-feed ratio (G:F) across treatments. In conclusion, dietary supplementation with 130 mg/kg nicotinamide improved oxidative status, oxygen transport capacity, inflammatory regulation, and gut microbial composition in finishing pigs fed low-protein diets, without significantly affecting growth performance. In contrast, higher supplementation levels exceeding 220 mg/kg may induce physiological stress, as indicated by elevated ALT levels. These findings suggest that 130 mg/kg is an effective and safe level for supporting health in finishing pigs on a low-protein diet.