The effects of dietary levels of corn distillers dried grains with solubles and supplementation of valine and isoleucine on growth performance, intestinal health, and cecal microbiome in Ross 708

The current study was conducted to investigate the effects of additional valine and isoleucine in a high corn distillers dried grains with solubles (DDGS) diet on growth performance, intestinal health, and cecal microbiome in broilers. A total of 800 0-d-old male Ross 708 were allocated into 5 dietary treatments with 8 replicates. The five diet groups were as follows: 1) corn-soybean meal (SBM)-based control (CON) group; 2) 15 % DDGS (15D) group (replacing corn and SBM with 15 % DDGS); 3) 15D + additional valine and isoleucine to have the same leucine:valine and leucine:isoleucine ratios as the CON group (15DB); 4) 30 % DDGS (30D) group; and 5) 30D + additional valine and isoleucine to have the same leucine:valine and leucine:isoleucine ratios as the CON group (30DB). The reduction in growth performance, carcass weight, breast muscle, and lean weight was intensified with increasing dietary DDGS levels. The 15DB group showed similar body weight gain (BWG) and carcass weight compared to the CON group. The 30DB group showed significant differences in phylum- and family-level cecal bacterial diversities compared to the 30D group but did not create significant growth improvement. No significant differences were observed in growth performance, carcass weight, body composition, intestinal morphology, jejunal gene expression levels, and alpha and beta diversity of cecal microbiota between the 15D and 15DB, and 30D and 30DB groups. Additional valine and isoleucine did not show consistent improvements in intestinal health and growth performance in DDGS-supplemented diets. The effect of additional valine and isoleucine varied depending on how much corn and SBM was replaced with DDGS in the diet, which may have been affected by additional factors other than intestinal health. In conclusion, additional valine and isoleucine may play a role in growth and muscle deposition but not have significant impact on the intestinal health in broiler diets that replaced corn and SBM with high levels of DDGS. Keywords: Branched-chain amino acids; Broiler; Corn distillers dried grains with solubles; Gut health; Microbiome.