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Our objective was to explore the synergy between sexed semen and in vitro embryo production and assess benefits of these technologies on commercial farms. Ovaries were collected from high genetic merit Holstein cull cows via colpotomy or at the time of slaughter. Oocytes were aspirated from the ovaries, fertilized 20–24h later, and matured to the morula or blastocyst stage. Embryos were transferred into recipient Holstein cows and heifers on the same farms. Seven Wisconsin herds participated, and 365 embryos were produced from 104 donor cows. Only 272 of these embryos were transferred due to limited availability of recipients. Sexed semen from three Holstein sires was used. On average, 3.5±0.37 transferable embryos were produced per donor, including 1.4±0.18 grade 1 embryos and 1.5±0.20 grade 2 embryos. Individual farms averaged from 1.6 to 5.8 transferable embryos per donor. Laboratory data also revealed interesting results. On average 43.7±4.0 oocytes were collected per donor, and the number of usable oocytes (33.9±3.4), and percent embryos cleaved (52.1±1.9), were significant predicators of the number of blastocysts developed. We divided the usable oocytes and embryos cleaved per donor into quartiles. The fourth quartile for embryos cleaved was significantly greater (P&amp;lt;0.05) than the lower three quartiles, and the usable oocyte quartiles all significantly differed from each other. Semen freeze date was also a significant predicator of the number of blastocysts developed, suggesting significant variation in the quality of sorted semen per ejaculate. To preliminarily test the effect of sorting on the percentage of embryos developing to blastocyst stage, oocytes were recovered from ovaries collected at a slaughterhouse and fertilized using non-sorted semen or sex-sorted semen from the same sires. Oocytes (n=3312) fertilized using non-sorted semen tended (P=0.06) to produce more embryos developing to blastocyst stage than oocytes (n=1577) fertilized using sex-sorted semen (20.1±2.9% v. 12.2±2.3%, respectively). Preliminary pregnancy results show strong farm and sire effects. Overall conception rate was 36% for heifer recipients and 18milking cow recipients. These results suggest that low cost in vitro embryo production may have promise as an early system for utilizing sexed semen in dairy cattle breeding programs.

287IN VITRO PRODUCTION OF HOLSTEIN EMBRYOS USING SEX SORTED SEMEN