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Abstract
Summary and conclusion
The present study was carried out at the Rabbits Research Unit, Department of Animal and Fish Production, Faculty of Agriculture (Saba Basha), Alexandria University, during the period from October 2004 to March 2005.
A factorial design (2 X 3 X 2) was applied in this experiment, to study the effect of three ambient air temperatures with or without ascorbic acid supplementation on productive and reproductive performance, blood constituents, digestibility coefficients and carcass quality of NZW and CHN rabbits.
Rabbits of each breed were assigned randomly into three environmental temperatures, 12 in each (8 females and 4 males). The first group was subjected to normal air temperature (15-19 oC); the second and third groups were exposed to two level of heat (26-27 and 32-34 oC). The duration of heat exposure was six hours daily, from 10 am to 4 pm, each of the 3 temperature group was allotted to 300 mg ascorbic acid/ litter drinking water (with/ or without).
The results obtained could be summarized as follows:-
1- CHN rabbits had higher values of respiration rate (RR) than NZW rabbits by about 4.65%. Rabbits reared under high temperature recorded significantly higher values of (RR) and rectal temperature (RT) than those under normal or medium temperature. In general the supplementation of rabbit’s drinking water by Vit C significantly decreased their RT and RR. Reared CHN and NZW rabbits under high or medium temperature showed a significant increase in both RR and RT of these rabbits, However, Vit C supplementation significantly decreased the bad effect of heat stress on these physiological parameters.
2- CHN doe rabbits had significantly the longest gestation period, and higher values of litter size at 21 and 28 days of age than NZW doe rabbits. Doe rabbits reared under normal temperature recorded significantly decreased gestation period (2.71%) and increased bunny weight, litter weight, litter size at 21 (25.23, 26.35, 55.74%) and 28 (60.59, 41.89, 43.82%) days of age as well as improved vaibility (12.14%) more than high temperature. Vit C supplementation caused significantly decreased on gestation period and on the same time, increased bunny weight, litter weight and litter size at 21 and 28 days of age and viability % (brith-21 days). CHN doe rabbits exposed to normal temperature and drank water with Vit C recorded the highest values of litter weight at 21 and 28 days of age but heat stressed NZW doe rabbits having no Vit.C recorded the lowest values of viability%.
3-In general, NZW bucks had better ejaculate volume, pH, mass motility, individual motility, live and normal spermatozoa and total sperm output per ejaculate than CHN rabbits. Ejaculate volume, mass and individual motility, sperms concentration, total output and live and normal sperms were significantly higher in bucks reared under normal temperature than those reared under heat stress, While, bucks reared under heat stress recorded the highest values of pH, seminal plasma ALT. Ascorbic acid supplementation significantly improved ejaculate volume, pH, mass and individual motility, sperm concentration, live sperm and total output by about 3.11, 1.96, 18.09, 19.14, 4.12, 9.48 and 34.20% respectively and significantly decreased seminal plasma ALT by about 8.82% as