Transfer of Bovine Blastocysts Derived from Short‐term In Vitro Culture of Low Quality Morulae Produced In Vivo

Abstract

The aim of this study was to evaluate if blastocysts arising from in vitro culture of Grade 3 bovine morulae produced in vivo can promote acceptable pregnancy rates when transferred into recipients. Embryos of different stages and qualities were recovered from superovulated Bos taurus and B. indicus donors. Grade 3 morulae were cultured in either Holding Plus or TCM-199 (supplemented with 10% bovine fetal serum) media for 24 h at 38.5 degrees C. After this culture period, the resulting blastocysts were morphologically classified (Grades 1, 2 and 3) and transferred into recipients previously synchronized with the donors. Non-cultured Grades 1 and 3 morulae were used as control. Pregnancy diagnosis was carried out 60 days after embryo transfer and the data were analysed by logistic regression, considering variables, such as embryo quality (Grade), donor breed, culture medium, donor-recipient synchrony and seasonality. Embryo quality was the only variable, showing significant effect on the pregnancy rate. Pregnancy rates for non-cultured Grade 1 and 3 morulae, and blastocysts arising from cultured Grade 3 morulae were 58.1% (n = 31), 17.1% (n = 35) and 51.1% (n = 47), respectively (p < 0.05). There were no statistical differences between non-cultured Grade 1 morulae and cultured blastocysts. Pregnancy rates for Grades 1 (65.0%) and 2 (60.0%) were higher than Grade 3 (29.4%) cultured blastocysts (p < 0.05). It was concluded that short-term in vitro culture is a very convenient method of identifying morphologically low quality morulae with higher chances of continuing development after the transfer into recipients.

Insulin-like growth factor 2: A modulator of anti-apoptosis related genes (HSP70, BCL2-L1) in bovine preimplantation embryos

“…In accordance, total blastocyst cell numbers and mean ICM proportion were also found to be greater in excellent-and good-quality blastocysts than those in poor quality; however, the mean ICM proportion only showed significant differences between excellent-and poor-quality blastocysts. There is good evidence that blastocyst proliferative potential and relative lineage sizes influence subsequent growth and viability of the embryo [4,28,59]. These findings are consistent with other reports indicating that the mean cell number and proportion of ICM of blastocyst recovered in vivo or in vitro decreased with reduction in embryo quality [60][61][62].…”

“…Despite the subjectivity of the morphological evaluation, embryo quality is known to be associated with pregnancy outcomes [28]. Accordingly, decrease in blastocyst cell number and increase in blastocyst apoptotic index, which evidenced in morphologically poor-quality blastocysts, have been attributed to imbalance in gene expression [5,6].…”

Effect of oestrous synchrony between embryo donors and recipients, embryo quality and state on the pregnancy rate in beef cattle

“…() emphasized the importance of embryo quality to obtain reasonable results, as embryos in good condition showed significantly better pregnancy rates when compared to embryos of poorer quality. There is a positive relationship between the morphological quality of embryos and the subsequent pregnancy rate (Alvarez, Meneghel, Martinez, Pires, & Schammass, ).…”

Taxa de gestação após transferência de embriões bovinos produzidos in vitro

“…Dessa forma, a qualidade do embrião apresenta-se como um fator de grande relevância para o sucesso dos programas de transferência de embriões. Tendo em vista que, a classificação da qualidade embrionária pode ser realizada mediante análise microscópica de critérios morfológicos, como a coloração das células, a homogeneidade e tamanho dos blastômeros, a granulação citoplasmática e o grau de fragmentação dos blastômeros (Alvarez et al, 2008). Ainda, com base em critérios morfológicos a Sociedade Internacional de Transferência de Embriões, elaborou um guia de classificação de qualidade e/ou viabilidade do embrião em quatro graus, sendo eles: grau 1: excelente ou bom; grau 2: regular; grau 3: ruim e grau 4: morto ou degenerado (Stringfellow;Seidel, 1998).…”