Effects of cottonseed meal bioactive peptides on growth performance, ileal digestibility, serum amino acid and immune responses of broiler chickens.

1. The influence of different inclusion levels of a bioactive peptide derived from cottonseed meal by enzymatic hydrolysis was examined in broilers. Experimental diets contained six inclusion levels of cottonseed bioactive peptides (CBP) at 0, 2.5, 5, 10, 15 and 20 g/kg of diet. A total number of 432, one-day-old broiler chicks (Ross 308) were randomly allocated to one of six treatments, which were replicated six times based on a completely randomised design.2. The results showed that CBP in the diet linearly increased body weight gain feed consumption and so FCR. As a result of the higher feed intake, CBP linearly (p < 0.05) increased FCR. However, when corrected for the body weight differences (d 35), there was no significant effect of CBP on FCR.3. The CBP inclusion improved crude protein and Arg, His and Met ileal digestibility in a linear manner (p < 0.01). Serum concentration of Lys, Trp, Ala and Orn decreased linearly (p < 0.05) as the concentration of CBP increased in the diet.4. Antibody titres against Newcastle disease, sheep red blood cell (SRBC) and serum concentration of IgY, IgM, IgA and GSH, red blood cell count and haematocrit increased in line with CBP inclusion.5. There was both a linear (p = 0.001) and quadratic (p = 0.021) response for carcase yield percentage, although the liver's relative weight linearly (p = 0.001) decreased with higher CBP inclusion.6. Overall, the data showed that dietary supplementation of CBP in broiler diets has the potential to improve performance traits, ileal protein and amino acid digestibility and can be used as a novel functional protein in poultry diets.