Influence of vitamin E, tryptophan and β-glucan on growth performance, meat quality, intestinal immunity, and antioxidative status of yellow-feathered chickens fed thermally oxidized oils

Abstract

Industrial oil wastes have been suggested as lower-cost alternative energy sources in place of refined oils for broiler chickens, but negative effects on performance and antioxidative status have been reported. This experiment was carried out to assess the influences of dietary inclusion of thermally oxidized soybean oil (OSO) with or without supplementation with vitamin E, tryptophan and β-glucan on growth performance, meat quality, plasma indices, jejunal antioxidative status, and jejunal gene expression of yellow-feathered male chickens aged 43 to 63 days. A total of 900 male Lingnan chickens at 43 days of age were randomly assigned to 6 treatments, each of which consisted of 6 floor pen replicates of 25 birds (n = 150/treatment): (1) A basal diet (BD) containing 3.5% fresh soybean oil (SO) (control); (2) BD containing 3.5% OSO replacing fresh oil (3.5%OD), (3) BD with 7% OSO (7%OD); (4) 7%OD + 100 mg vitamin E/kg (VE diet); (5) 7%OD + 0.02% tryptophan (tryptophan diet), and (6) 7%OD + 100 mg β-glucan/kg (β-glucan diet). The results showed that the growth traits and plasma variables (triglycerides, cholesterol, uric acid, creatine kinase, lactate dehydrogenase, reduced glutathione-GSH, oxidized glutathione-GSSG, malondialdehyde-MDA, and diamine oxidase-DAO) were not affected by the diet. The jejunal mucosal activity of alkaline phosphatase, inducible nitric oxide synthase, gamma-glutamine-cysteine synthetase, and glutathione S-transferase, or contents of GSH, GSSG and MDA were not affected by the treatments, but the activity of DAO of the control and β-glucan treatments were the highest (P < 0.05), followed by that of tryptophan treatment (P > 0.05), and those of 3.5%OD, VE diet, and 7%OD (P < 0.05). The expression of jejunal nuclear factor erythroid derived 2, peptide transporter 1, and zonula occludens 1 did not differ significantly (P > 0.05) among the treatments. There were no significant effects (P > 0.05) due to the diet on breast meat pH (45 min or 96 h post-mortem), shear force, intramuscular fat, drip loss (96 h), MDA, GSSG, meat a* and b* values (45 min), or meat a*, b*, and L* (96 h), but the L* value (45 min) of the β-glucan treatment was the highest (P < 0.05), followed by those of VE diet, tryptophan treatment, and 7%OD (P > 0.05) then 3.5%OD and the control (P < 0.05). Drip loss (24 h) in the breast muscle of the tryptophan treatment was the highest (P < 0.05), followed by that of β-glucan (P > 0.05), then 3.5%OD, VE diet, 7%OD, and the control (P < 0.05). The treatments did not affect (P > 0.05) intramuscular fat or drip loss (24 h) in the thigh muscle, but drip loss (96 h) of 3.5%OD was the highest (P < 0.05), followed by that of tryptophan treatment (P > 0.05), then 7%OD, VE diet, control, and β-glucan (P < 0.05). Collectively, up to 7% lightly oxidized soy oil can be incorporated successfully in the finisher diet of male Lingnan chickens (d 43 to 63 d) as a lower cost energy source in place of fresh SO. Additional supplementation with β-glucan, VE and tryptophan had no notable benefits.