Development of sheep morulae in a simple or sequential medium: relationship between morphological evaluation and embryonic viability

Abstract

In vitro embryo production (IVEP) has the potential to generate a large number of domestic animal embryos, as well as the implementation of other technologies from IVEP, such as transgenesis and cloning. The embryos produced in vitro are evaluated through morphological characteristics, but it is of great importance to determine if this evaluation corresponds to the viability of the embryos. The objective of the present study was to determine the relationship between the morphological evaluation and morula viability obtained in a single culture medium (SCM) or sequential medium (QCM) at 120 hours. The percentage of embryo division was 85 % in both culture media and morula percentage of 49 and 45 % for SCM and QCM, respectively (p>0.05). A higher number of quality one and two morulae was obtained in SCM compared to QCM (31 % and 44 % versus 13 % and 27 %, respectively) (p<0.05). It was not the same in quality 3 morulae, where SCM was higher than QCM (50 % and 18 %, respectively) (p<0.05). The total percentage of transferable morulae in SCM and QCM was 93 % and 90 %, respectively. The percentage of viable morulae was 98 % in both media, based on the number of viable blastomeres per morula, which were similar in SCM and QCM (14 ± 2 and 13 ± 2, respectively, p> 0.05). A positive correlation between the morphological quality and the viability of their blastomeres in morulae cultured with SCM and QCM (0.7415 and 0.7408, respectively) was determined.  It is concluded that there is no difference between morulae obtained from SCM and QCM, but based on costs and embryons manipulation, SCM may be the best choice. The morphological evaluation of the embryos produced in vitro is a reliable method and the presence of vesicles in the blastomers did not affect the embryonic viability.

Keywords: simple and sequential culture medium, morphological evaluation, embryonic viability, ovine morula.