Comparison of Stereoscopy, Light Microscopy and Ultrastructural Methods for Evaluation of Bovine Embryos

Abstract

The most important point in embryo transfer success is the evaluation of the stage of development and quality of embryos. Therefore, the purpose of this study was to compare the morphological evaluation of embryos using stereoscopy, light microscopy and electron microscopy in order to establish the accuracy of former method compared with more invasive and accurate procedures. For this purpose, 23 Brahman x Swiss cows were used and synchronized with Norgestomet 6 mg plus, 5 mg Estradiol valerate (Syncromate B(R), Rhone Merieux, Mexico, Mexico City) and superovulated with Folltropin-V 240 mg (Vetrepharm, Mexico, Mexico City). Non-surgical embryo collection was performed 7.5 days after insemination. Descriptive statistics analysis was used to assess the data. Seventy-eight embryos were collected and classified by stereoscopic microscopy, finding 51.2% (40) of good quality, 25.6% (20) fair and 24.3% (19) poor. Later, under light microscopy observation, evaluation of the same embryos resulted in 25.6% (20) good, 32.0% (25) fair and 42.3% poor quality. Finally, in the evaluation of embryos under electron microscopy 24.3% (19) were found to be of good quality, 29.3% (23) fair and 46.1% (36) poor. Evaluation of embryos with stereoscopic microscopy was found to be very subjective, as nearly 50% of embryos classified by this method as good quality, showed features of degenerative stages under light and electron microscopy. Embryos with these features are generally frozen and transferred, which could be one of the reasons for having low fertility rate in embryo transfer programmes.

Effects of oocyte quality and semen donor on the efficiency of <i>in vitro</i> embryo production in cattle

“…Immature oocytes are routinely selected for IVM by visual assessment of morphological features. Although morphological criteria provide a reasonable means of identifying oocyte quality and suitability for IVM, there is evidence that morphological criteria are not suffi cient for selection of oocytes of superior developmental potential (Aguilar et al, 2002;Han et al, 2006;Bols et al, 2007). It was clearly demonstrated that immature oocytes selected by similar morphological features differ in their developmental potential.…”

Crucial surviving aspects for vitrified in vitro-produced bovine embryos

“…In the literature, there is still no consensus as to the optimal development stage for embryo cryotolerance (Saragusty & Arav, 2011). Moreover, embryos classified as good quality, according experienced technicians following established criteria (Lindner & Wright, 1983) showed degenerative stages features under electron microscopy in 30% of the cases (Aguilar et al, 2002). Farin et al (1995) have proved the subjectivity of the stereoscopic evaluation by showing that embryos that were classified as being of high quality by the time they were frozen, were in fact in due process of degeneration when assessed by more accurate techniques.…”

Observation of freshBos indicusembryos comparing stereoscopic and phase contrast microscopy

“…These results agree with observations by Callesen et al (1995), who reported that embryos evaluated at a more advanced, as opposed to early developmental stages, have better quality and are easier to assess with precision. Aguilar et al (2002) reported up to 30% variability in evaluation criteria being the highest in embryos judged as being of moderate quality. This disagreement in evaluations has also been found in other studies.…”