1Department of Animal Reproduction and Artificial Insemination, Veterinary Research Division, National Research Center, Cairo, Egypt
2Department of Clinical Pathology, Faculty of Veterinary Medicine, Cairo University, Egypt
Receive Date: 30 November 2010,
Revise Date: 15 February 2011,
Accept Date: 25 February 2011
Heat stress (HS) often blamed for suboptimal reproductive efficiency and is a worldwide problem, which inflicts heavy economic losses reflected in limiting the breeding season of rabbits to be normally from September to May in northern hemisphere and subtropical regions. The present experiment was conducted to study the effect of summer heat stress and the alleviating effect of some antioxidants on semen characteristics and the serum and seminal plasma oxidative/antioxidative status of New Zealand White (NZW) rabbit bucks. Forty-eight fertile NZW white bucks were randomly divided into six equal groups (n=8),first two groups served as control (summer heat stressed and winter) groups, the others, orally administrated ascorbic acid 40 mg/kg bw/d, zinc methionine 10 mg/kg bw/d, coenzyme Q1010 mg/kg bw/d and L-carnitine 40 mg/kg bw/d. Blood and semen samples were collected once weekly among experimental period. Routine spermogram was performed. Lipid peroxidation, total antioxidant capacity and catalase activity in both serum and seminal plasma were assayed. The climatic data were continuously recorded among the experimental period and the weekly average temperature-humidity index (THI) was calculated. Summer HS adversely affected both qualitative and quantitative traits of spermogram but bucks remain within fertile limit. Thiobarbiric acid reactive substances (TBARS) showed a significant increase while total antioxidant capacity (TAC) and catalase showed significant decreases. Contrary to our expectation, selected antioxidants did not restore these parameters to their winter levels. It was concluded that zinc and L-carnitine were found to be the most beneficial antioxidants in the relief of spermogram of HS-induced effects. Serum and seminal plasma oxidative/antioxidant statuses followed an identical pattern in response to heat stress. Taking the current results into consideration, it can be stated that an adequate reproductive performance in NZW rabbit bucks can be achieved in summer and from the scientific point of view, it is not obligatory to stop breeding in summer months.
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