The results of this study confirmed that reducing the dietary CP level associated with AA supplementation could
improve the utilization of dietary nitrogen in piglets. Intestinal morphology and some digestive enzyme activities were not influenced when dietary CP concentration was reduced from 23.1 to 18.9% in weaned pigs. However, some amino acids may be at insufficient levels to meet piglet requirements when reducing dietary CP concentration from 23.1 to 17.2%. This resulted in reduced feed intake, villous atrophy and reduction of some digestive enzymes activities leading to poor performance during the immediate post-weaning period. Therefore, the ideal protein profile should be further studied in low-protein diets and the correct balance of arginine or glutamine may be required to ensure optimal gut development and performance in weaned piglets when reducing dietary CP concentration from 23.1 to 17.2%.