The effects of a phytogenic feed additive versus an antibiotic feed additive on oxidative stress in broiler chicks and a possible mechanism determined by electron spin resonance and The effect of allopurinol, uric acid sodium salt administration, and inosine on xanthine oxidoreductase activity and plasma uric acid in broilers.

摘要

The purpose of the first study was to compare a phytogenic feed additive and an antibiotic feed additive when measuring oxidative stress in young broilers. Phytogenic feed additives are plant-derived products used in poultry feeding to improve overall performance of broilers. Although the precise mechanism by which the increased growth rate is realized remains uncertain, these products have antioxidant components that are known to reduce oxidative stress. This is considered important in that reactive oxygen species (ROS), the causative factor of oxidative stress, can result in damage to biological systems within the bird. In this study, 588 one day-old Cobb 500 chicks of mixed sex were fed one of four diets and housed on either dirty or clean litter for 3wks. Litter was analyzed for microbial content and provided evidence of a substantial microbial challenge. Treatments included : Group I (starter diet with no additive and housed on clean litter), Group II (a starter diet with no additive and housed on dirty litter), Group III (starter diet with a .05% inclusion of BMD (bacitracin methylene disalicylate)), or Group IV (a starter diet with a .05% inclusion of Biostrong 505 plusRTM). The study was designed around a random block assignment of treatments allocated to groups of twenty-one birds per pen. Blood samples were obtained from chicks at 18 days of age for measurement of leukocyte oxidative activity by a bioluminescence technique. Results of the study showed that chicks in the treatment groups fed the phytogenic additive (PFA) had lower levels of oxidative stress (P0.02). Once this was determined, electron spin resonance (ESR) spin trapping was used to detect and measure hydroxyl or superoxide radical reduction by the feed additives. Fenton chemistry was utilized for production of hydroxyl radicals and a xanthine/xanthine oxidase reaction for the production of superoxide radicals. Both systems were used again in RAW 264.7 mouse peritoneal monocytes. Results from both systems showed that the phytogenic additive scavenges hydroxyl radicals almost as efficiently as the antibiotic additive (P&le0.05). The results from the study suggest that the effectiveness of the phytogenic feed additive is due, in part, to its ability to reduce oxidative stress in growing broiler chicks.The purpose of the second study was to measure xanthine oxidoreductase, an enzyme responsible for uric acid production, in broilers given a known inhibitor to the enzyme. The inhibitor, allopurinol, is known to dramatically decrease uric acid in birds, which is a potent antioxidant for avian species. The loss of uric acid concentrations will potentially leave the tissues more susceptible to damage by reactive oxygen species.Xanthine oxidoreductase (XOR) has two forms in the avian, xanthine dehydrogenase (XD) and xanthine oxidase (XO). The purpose of these studies was to determine the effects of allopurinol and inosine on plasma uric acid and enzyme activity. In the second study, Cobb x Cobb (n=15 5weeks old) were separated into three treatments (n=5) control (CON), INO (inosine at 161g/kg feed), or INOAL (inosine and allopurinol 50mg/kgBW). There was a significant increase (p=0.005) in total enzyme activity of the liver in the INO birds. INOAL birds had a significantly lower (p=0.005) uric acid concentration in the liver. The reduced uric acid concentration in the liver suggests that there is a residual effect of allopurinol, which potentially results in lowered antioxidant activity in this tissue.