TRANSFER OF CRYOPRESERVED BOVINE EMBRYOS: EFFECT OF BLASTOCENTESIS

Abstract

Pregnancy rate obtained with bovine embryos cryopreserved by slow curve (CL) and vitrification (VT) do not exceed 40 %; therefore, the search continues for other alternatives to increase pregnancy rate, such as blastocentesis (Blx), which results in a post-thawing survival rate in human and mice embryos of ?70 %. The hypothesis was that the post-transfer gestation rate (TG) of cryopreserved bovine embryos produced in vivo, with or without blastocentesis, is higher for embryos cryopreserved by VT than for those cryopreserved by CL. The objective was to determine the effect of the cryopreservation (CR) and the Blx method on the post-transfer gestation rate of bovine embryos produced in vivo. The experimental design was a completely randomized 22 factorial arrangement, with sample size of 100 embryos produced in vivo, and the factors were CR and Blx with 25 repetitions per treatment: T1) CL, T2) VT, T3) CL?Blx, and T4) VT?Blx. Ovulation was synchronized in the recipients through natural progesterone (CIDR-B?) to perform embryo transfer at a fixed time and the diagnosis of pregnancy was made 45 d post-transfer. The response variable was the TG per treatment and it was analyzed by the ?2 method to determine the homogeneity of the proportions in treatments. The general TG obtained was 34 %. TG was higher with VT embryos (64 %) than with CL embryos (8 %), without previous Blx (p?0.05). The Blx increased TG in CL embryos (T1: 8 % and T3: 44 %; p?0.05) and decreased in VT embryos (T2: T4 64 % and 20 %; p?0.05). VT and Blx are alterna