Cryopreservation of rabbits spermatozoa: effects of cryprotectant agents, clarified egg yolk and post-thawing incubation time [electronic resource].

Includes references.

One hundred and six New Zealand White (NZW) and Baladi Black (BB) doe rabbits aged 6 months were used in this study during two periods. Thirty NZW and 26 BB rabbits and other 30 NZW and 20 BB rabbits were used in the 1st (May-October 2003, hot climatic) and second (November-April 2004, mild climatic) periods, respectively. In each period, the animals in each breed were divided into two equal groups according to the housing system. The first group was raised in semi-closed rabbitry and the second was housed in open rabbitry under shed. The estimated temperature-humidity index values indicating exposure of rabbits raised in semi-closed building to very severe heat stress and those raised under shed exposed to moderate heat stress during the hot period and absence of heat stress in the mild period. Thermoregulatory and hematological response, plasma estrogen (E2) and progesterone (P4) concentrations, abortion percentage, litter and bunny weight traits were (P<0.01 or 0.05) adversely affected by semi-closed housing system and hot climatic period. Most of the studied traits were significantly (P<0.001, 0.01 or 0.05) higher in NZW than in BB rabbits. Rectal temperature, E2 levels, number of service per conception and abortion percentage were significantly (P<0.001, 0.01 or 0.05) increased with advanced parity. During mild climatic period, NZW does raised in semi-closed system showed the best (P<0.001, 0.01 or 0.05) thermoregulatory and hematological responses, and values of E2 and P4 concentration and consequently best reproductive efficiency and litter traits, followed mostly by those housed in open system than BB does rabbits. Mortality rate from birth to weaning was higher in NZW or BB rabbits raised in open system than those housed in semi-closed systems during mild period. Hot climatic condition period adversely affected performance of NZW rabbits raised in the semi-closed system markedly than BB rabbits, however, housing NZW does in the open system during hot period alleviated heat stress and improved their performance. The performance of BB rabbits housed in open or semi-closed systems during hot period were nearly similar in most of parameter studied. These results proved the superiority of the open system during hot period, since physical properties of building materials and environmental conditions under shed are reflected markedly on the rabbits performance as proved by both physiological reactions and biological responses which are the most and accurate indicators for rabbits welfare.

Summary in Arabic.

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