Abstract
The management of sheep reproduction requires the induction and synchronization of the estrus cycle and ovulation for the ewe out-of-season and/or synchronized lambing. These managements are based on the insertion of an intravaginal device of controlled internal drug release (CIDR or sponge) and then the administration of a hormonal injection, such as PMSG, eCG, hCG, or GnRH. This study aimed to compare the impact of CIDR or sponges, with PMSG and GnRH injection, respectively, for inducing estrus synchronization, lambing rate, twining, and sex preselection rate in Naimi sheep. A total of 86 Naimi sheep ewes and six male rams with proven fertility were used in this study. The results showed that the first ewes or CIDR group had the highest ewe fertility rate of 26/28 (92.59%) with a 35/92 (38.04%) lamb production ratio. The offspring sex ratio was 22/35 males (62.85%) and 13/35 female lambs (37.14%). Their twin ratios were 9/22 (34.4%), producing 14 males (77.77%) and 13 females (37.14%). The second or sponge ewe group's fertility ratio was 16/26 (61.53%). They sired the lowest offspring ratio of 20/92 total lambs (21.73%) and had sex ratios of 11/20 males (55.0%) and 9/20 (45.0%) female lambs. The twin production ratios were 4/22 (25% with two males and two males with female twins). Their twin sex ratio was six males (77.77%) and two females (22.34%). The third or control ewe group's fertility rate was 29/33 (87.87%). They produced 37/92 (40.27%) lambs, and the total sex ratios were 22/37 male lambs (59.45%) and 15/35 (40.45%) female lambs. They produced eight twins (27.58%), and their twins' sex was equal to six male and six female (50%) lambs. Regarding the progesterone and testosterone hormone levels, no differences during pre- or post-intravaginal insertion were observed, but the estrogen level showed some differences during pre-insertion. In conclusion, the use of CIDR with hormone injection is better for reproduction management, male lambing, and sex preselection rate. The control group produced approximately the same fertility rate with equal male and female lambing sex preselection rates.