RESUMO
This experiment aimed to discover the effect of reducing dietary protein supplemented with lysine, methionine, and threonine on growth performance, volatile fatty acid profile, and intestinal villus height and crypt depth of broilers, as well as the microflora counts isolated from broiler chicken faeces. A total of 288-day-old broilers were allocated to eight treatments with six replicates consisting of 36 birds per treatment. The diets contained dietary protein from 21 to 18% in starter diet and 18 to 16% in finisher diet supplemented with L-lysine, DL-methionine, and L-threonine at the same ratio for all dietary treatments. Body weight and feed intake were determined, and feed conversion ratio was calculated. Blood, intestine, and digesta samples were collected at 21 and 42 days for further analysis. Dietary protein supplemented with amino acids improved growth performance, reduced pathogenic bacteria, and increased beneficial bacteria counts, small intestine villi height and crypt depth, and ileal-digesta volatile fatty acid concentrations of broiler chickens. However, reducing 2% of dietary protein supplemented with lysine, methionine, and threonine showed the best results, especially in growth performance, feed conversion ratio, microflora count, duodenal and jejunal villi height, and ileal-digesta volatile fatty acid concentrations, such as butyric and valeric acids. It is believed that by reducing the level of dietary protein in broiler diet while supplementing with synthetic amino acid may enhance the intestinal morphology, nutrient digestibility, and absorption in broiler chickens and will simultaneously result in better performance.(AU)