Transvaginal ultrasound-guided cumulus oocyte complexes aspiration and in vitro embryo production in suckled beef and lactating dairy cattle on pasture-based management conditions.

This study was conducted to determine the use of repeated transvaginal ultrasound-guided cumulus oocyte complex (COC) aspiration on COC recovery rate, in vitro embryo production (IVP) and subsequent pregnancy rates in Holstein Friesian (HF) and Aberdeen Angus (AA) cows (Experiment 1), and in pregnant and non-pregnant Holstein Friesian cows (Experiment 2). Cycling, non-pregnant HF (n=17) and AA (n=32) cows with 40-70 days postpartum, between 3 and 5 years of age were used in the Experiment 1. All cows were submitted to repeated transvaginal ultrasound-guided COC aspiration twice a week for 5-7 weeks. Cumulus ooctye complexes (COC) were in vitro matured, fertilized and cultured for 8 days. An overall of 100 and 350 embryos from HF and AA cows respectively were cryopreserved using a conventional slow freezing (Experiment 1). A total of 81 and 285 frozen-thawed embryos from HF and AA cows respectively were transferred to recipient cows. Pregnancy diagnosis was performed at 60 and 150 days of gestation using transrectal ultrasonography. In Experiment 2, cycling non-pregnant (n=9) and pregnant (n=8) HF cows were submitted to repeated ultrasound-guided COC aspiration and COC were in vitro matured, fertilized and cultured as in Experiment 1, except that embryos were cryopreserved but not thawed and transferred as described for Experiment 1. The results of this study indicate that COC recovery rate and blastocyts production are affected by the breed of the donor cow. The quality of blastocyts produced from both breed did not differ in terms of pregnancy and calving rates (Experiment 1). The physiologic state of pregnancy did not affect COC recovery rate and blastocysts production per donor/session (Experiment 2). The use of ultrasound-guided COC aspiration and IVP could be a powerful technique to improve the genetic of beef and dairy cattle managed under pasture-based conditions management in the southern Chile.