Effect of dietary onion (Allium cepa L.) powder as an antioxidant on semen quality, blood biochemicals, and reproductive parameters, as well as immunological variables of rabbit bucks under severe heat stress.

This study aimed to evaluate the antioxidant effects of onion (Allium cepa L.) powder on the immunological variables, redox state, and semen quality of rabbit bucks exposed to severe heat stress. Thirty-six mature bucks (7 months old) were divided into three groups consisting of 12 bucks each, namely group I, control; group II, 400 mg onion powder/kg diet; and group III, 800 mg onion powder/kg diet. The quality of semen was evaluated for volume, pH, motility, concentration, total sperm output, viability, and packed sperm volume. Blood samples were collected in the 12th week for estimation of red blood cells (RBC), white blood cells (WBC), and erythrocytic indices. Serum proteins, glutamate oxaloacetate (GOT), glutamate pyruvate transaminase (GPT), urea, creatinine, testosterone, follicle-stimulating hormone (FSH), luteinizing hormone (LH), immunoglobulins, malondialdehyde (MDA), total antioxidant capacity (TAC), glutathione, superoxide dismutase (SOD), and catalase (CAT) were measured. The temperature-humidity index (THI) obtained was within the range of 28.85-33.08 indicating severe heat stress. The results show that mass and individual motility, concentration, total sperm output, sperm viability, and packed sperm volume were higher (P < 0.05) in groups II and group III, with group III having the highest (P < 0.05) levels compared to group I. Compared to group I, groups II and III had higher (P < 0.05) concentrations of RBC, MCV, MCH, FSH, LH, SOD, and catalase. The highest concentration (P < 0.05) of GPT was obtained in group III compared to other groups. The highest concentration of IgG (P < 0.05) was obtained in group II while the lowest was in group I. In conclusion, dietary supplementation with onion powder at 400 or 800 mg/kg diet improves semen quality, RBC, FSH, LH, SOD, catalase, and IgG while ameliorating the adverse effects of heat stress and improve the health and reproduction of rabbits.
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