Effect of Different Levels of Cottonseed Meal Bioactive Peptides on Production Efficiency and Serum Antioxidant Activity of Broiler Chickens

Cottonseed meal was hydrolyzed using five types of enzymes: alkalase, chymotrypsin, pepsin, trypsin, and pancreatin. The experiment was carried out using 240 male broilers of Ross 308 strain in a completely randomized design with 4 treatments and 5 replications from 1 to 35 days of age and during the starter (1-15 days) and grower (16-35 days) phases. The experimental diets were the control diet, the control diet containing zinc bacitracin (70 mg/kg), and the experimental diets containing 15 or 20 g/kg cottonseed bioactive peptides which replaced equal amounts of corn and Soybean in the diet. Feed intake, weight gain and feed conversion ratio were measured and calculated for each cage (repetition) during three rearing (starter, grower and total period). At 35 days of age, 3 ml blood was obtained from the wing vein of 3 birds per replicate to measure serum antioxidant parameters. At the end of the rearing period, three birds from each cage were individually weighed and slaughtered and the relative weights of carcass, gastrointestinal and lymphoid organs as well as the length of different parts of the small intestine were measured. In the whole of the experimental period, the highest and lowest weight gain was observed in the antibiotic and the control groups, respectively. Antibiotic and peptide fed groups had higher feed intake and feed conversion ratio than the control group. Serum nitric oxide levels were higher in the 15 g/kg peptide group than in the control group and the antibiotic group. Malondialdehyde levels were lower for antibiotic or peptide groups than in the control group, and glutathione peroxidase levels in the groups fed antibiotic or 15 g/kg peptide was higher than in two other groups. Serum superoxide dismutase levels were higher in the groups receiving antibiotics or different levels of peptide than in the control group and the total serum antioxidant levels were not affected by the experimental diets. Antibiotic or peptide administration significantly reduced abdominal fat compared with the control group. The results of the present study showed that the bioactive peptides produced by enzymatic hydrolysis of cottonseed meal improved the growth efficiency and antioxidant parameters of broiler chickens. These results suggest that the bioactive peptides of cottonseed meal have the potential to be used as an alternative to growth-promoting antibiotics in the broiler chickens diets.