الفهرس Only 14 pages are availabe for public view
 |  | from | 220 |  |  |
| | | from | 220 | | |
Abstract
The present experiment was conducted to study the effect of summer heat stress and the alleviating effect of some antioxidants on the hemogram, spermogram, serum and seminal plasma biochemical and hormonal parameters, and oxidative/antioxidative status of NZW rabbit bucks.
Forty-eight sexually mature NZW male rabbits were randomly divided into six equal groups. The study was performed in two experimental periods (winter and summer), each period lasted 12 weeks. In winter, one group was kept as a winter control group and received basal diet only. The other five groups were reared in summer and served as heat-stressed groups. Heat-stressed bucks were assigned at random to one of the following oral treatments:
1) Summer control group: basal diet + distilled water,
2) Ascorbic acid group: basal diet + 40mg ascorbic acid/kg bw/day,
3) Zinc group: basal diet + 10mg zinc methionine/kg bw/day,
4) Co enzyme Q10 group: basal diet +30mg Co enzyme Q10/kg bw/day and
5) L-carnitine group: basal diet + 40mg L-carnitine/kg bw/day.
The climatic data were continuously recorded among the experimental period and the weekly average temperature–humidity index (THI) was calculated.
Blood and semen samples were collected weekly. Two blood samples were collected from each animal, one for the hemogram and the othe for serum separation and biochemical analyses. Three ejaculates were collected for each buck. One served as row semen sample for spermogram. The other two consecutive ejaculates were pooled for seminal plasma separation which was stored at -80 °C until further analysis.
Season’s average temperature–humidity index (THI) was 18.52±0.22 in winter and 34.38±0.46 in summer, indicating absence of heat stress in winter and exposure to very severe heat stress in summer.
Hemogram profile revealed significant changes in summer groups with inconsiderable effect of used antioxidants. Summer heat stress adversely affected both qualitative and quantitative traits of spermogram but bucks remain within fertile limit. Of antioxidants used in the present study, zinc and l-carnitine were found to be the most beneficial antioxidants in the relief of heat stress-induced effects on spermogram.
Serum and seminal plasma biochemical components showed similar trends under heat stress (with some differences in the lipogram) but the effect was generally more remarkable on serum constituents. Such results may indicate that blood components were more sensitive to the effect of heat stress than the seminal biochemical components. Summer heat stress significantly increased glucose, AST, ALT and AcP activities, TL, total cholesterol, HDL and LDL-cholesterol values and significantly decreased TP, AlP and TG. Antioxidants administration alleviated some of the heat stress effects on such biochemical parameters.
In contrast to serum testosterone and cortisol which showed no changes in summer, seminal plasma testosterone and cortisol showed significant increase in summer group compared to winter group. Only ascorbic acid restored seminal plasma cortisol to the winter level.
Serum and seminal plasma oxidative/antioxidant status followed an identical pattern in response to heat stress. MDA showed a significant increase while TAC and catalase showed significant decrease. Contrary to our expectation, selected antioxidants did not restore these parameters to their winter levels.
It can be concluded from the present results that NZW rabbit bucks have continuous and acceptable spermatogenic activity and apparently normal body physiology during summer as well as during winter. The examined semen traits were not much inferior in summer compared to winter though seasonal variations in semen characteristics were detected.
Protective administration of zinc and l-carnitine caused significant improvement in rabbit sperm characteristics; meanwhile, ascorbic acid and co enzyme Q10 administration had no considerable enhancement in such concern.
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.