EFFECT OF HORMONAL eCG TREATMENT VERSUS REARING-FASTING PROGRAM ON EMBRYO RECOVERY, REPRODUCTIVE PERFORMANCE AND HORMONAL PROFILE IN NULLIPAROUS RABBIT DOES

The aim of this study was to determine the effect of hormonal eCG treatment versus rearing-fasting program on embryo recovery, reproductive performance and hormonal profile in nulliparous rabbit does. Does at 14 weeks old were randomly divided into three groups according to the estrus synchronization method before insemination; does fed ad libitum (control), does treated with subcutaneous 50IU of eCG 60 h before insemination (eCG), and does fasted 3 days per week (57% of feed ad libitum) then fed ad libitum one week before insemination (r-FP). In 23 of receptive does, serum estradiol-17β (E2) and leptin concentrations were determined at the time of insemination, and then embryos were recovered post-mortem at 72h postinsemination. A total of 51 receptive does were used to analyze the reproductive performance of all groups. The sexual receptivity and number of corpora lutea significantly increased in eCG group, however, high incidence of hemorrhagic follicles were observed. A significant increase in embryo recovery and donor rates was found in r-FP group compared with control, while no differences were observed in the number of normal embryos recovered per donor doe. The rate of embryos recovered in blastocyst stage significantly decreased in eCG group when compared with r-FP or control groups. The pregnancy rate, kindling rate and number of born alive were significantly higher while gestation duration and number of stillborn were significantly lower in r-FP does than those treated with 50 IU eCG. Serum E2 and leptin concentrations significantly increased in r-FP does in comparison with other groups. The global productivity of weaned rabbits in receptive does was significantly higher in r-FP than in eCG group. Results indicated that in conditions of this experiment, rearing-fasting program followed by one week feed flushing before the first insemination of rabbit does improves embryo recovery, reproductive performance and related hormones secretion. These results need to be confirmed in a larger scale and several reproductive cycles before recommending that method as an efficient biostimulation for estrus synchronization in nulliparous rabbit does.