Exploratory Assessment of N-Carbamylglutamate Supplementation on Feed Efficiency and Protein Utilization in Early Growing Pigs Fed Low Crude Protein Diet

Reducing dietary crude protein (CP) levels while supplementing with essential amino acids (AA) has been widely studied as a strategy to maintain nutrient balance while lowering nitrogen excretion. Among feed additives, N-carbamylglutamate (NCG), an arginine precursor with superior stability and mitochondrial permeability, has emerged as a promising feed additive for improving intestinal development and overall pig performance. A total of 240 crossbred grower pigs were allotted to four dietary treatments based on initial body weight. Treatments were arranged in a 2 × 2 factorial design with two levels of dietary CP (MCP, 16% moderate CP; LCP, 14% low CP) and two levels of NCG supplementation (WN, without NCG; NS, 0.1% NCG supplementation). Each treatment had 10 replicates, with six (3 male and 3 female) pigs per pen, and the feeding trial lasted for 4 weeks. Pigs fed the MCP diet tended to have higher final BW (<italic>p</italic> = 0.088) compared with the LCP diet. Feed efficiency was greater in MCP than LCP (<italic>p</italic> &lt; 0.05) and also tended to be enhanced in the NS (<italic>p</italic> = 0.089). CP digestibility tended to increase in the NS group compared with the WN (<italic>p</italic> = 0.093). The digestibility of arginine and tyrosine was increased in the NS group compared with the WN group (<italic>p</italic> &lt; 0.05). Furthermore, lysine (<italic>p </italic>= 0.067), glycine (<italic>p </italic>= 0.058), and the average of essential AA (<italic>p </italic>= 0.091) digestibility tended to be increased in the NS. The NS group showed higher concentrations of arginine, lysine, essential AA, non-essential AA, and total AA in the blood (<italic>p </italic>&lt; 0.05). Trypsin activity showed a tendency to increase in the NS group compared with the WN group (<italic>p</italic> = 0.087). In conclusion, dietary NCG supplementation in a low-protein diet showed potential to improve feed efficiency, AA digestibility, and serum AA profiles in early growing pigs.