Sex ratio of lambs born from assisted reproductive technologies
The objective of the present study was to investigate sex ratio of offspring resulting from superstimulated donors from two different breeds and artificially inseminated ewes from three different breeds. Romanov (n = 5) and Charollais (n = 6) (2 - 7 years of age) donors were superovulated using FSH-p with 400 mg NIH-FSH-P1 (total of 20 mg). Six days embryos were recovered surgically and grade 1 embryos (IETS classification) were frozen in ethylene glycol. Embryos (n = 154) were transferred into recipient ewes in pairs. A total 267 fat tailed ewes were synchronized (60 mg MAP and 600 I.U. PMSG) and inseminated with fresh diluted semen (10 x 107). Percentage for female sex ratio (64%) of offspring born from frozen thawed embryos differed significantly (P < 0.05) than expected ratio of 50:50. Lambing rates for recipient carried Romanov embryos (73.8%) was significantly higher (P < 0.05) than those carried Charollais embryos (57.1%). Pregnancy rates of artificially inseminated ewes were differed (P < 0.05) at time of insemination. Sex ratios of offspring were found similar among ewes with different breeds, inseminated in different times and with different vaginal mucus electric resistance. In summary, there is an advantage in the sex ratio obtained when using superstimulated ewes.