Optimal time for laparoscopic intrauterine insemination performed on ewes detected in natural heat.

The aim of this study was to optimize the laparoscopic intrauterine insemination (LAI) methodology by testing different time intervals between the natural heat detection and ewe insemination. Three experiments were performed in the breeding conditions of Southern Kazakhstan. Ewes (n = 243) were exposed for one hour to direct contact with the teaser rams (once a day, morning or evening). Ewes expressing behavioral symptoms of heat were detected and inseminated with the use of LAI during 210-1290 min (3.5-21.5 hrs) after heat detection. Reproductive traits of lambing rate (LR) and litter size (LS) were recorded according to the births registered at 137 to 152 days post insemination. Our statistical model showed significance only for the effects of ewe age category and the time interval from heat detection to LAI on the LR attribute. The highest LR (38.8%) was detected in ewes at 2.5-3.5 years of age. Corrected least-square means of LR indicated 18.5 hrs. as an optimal time for LAI of ewes in natural heat. In the present study, the percentage value of lambing rate obtained at 18.5 h interval was 70.7%. Therefore, our study suggested an effective methodology to spread valuable genetic information in the sheep population in the regions of extensive farming where heat cycle synchronization is not usually performed. Importantly, our study is among the first ones that follow the European strategy to eliminate the occurrence of hormones in livestock production and the environment.