289 IN VITRO PRODUCTION OF OVINE EMBRYOS FROM WOOL AND HAIR BREEDS

Abstract

In tropical areas, wool-less or haired breeds of sheep are more prolific than wool breeds. There are no reports about IVF in tropical breeds; therefore, it is not known how these respond under IVF conditions. Developing protocols for in vitro production of embryos in haired breeds could contribute to the preservation and use of their genetic potential in tropical countries where they are economically important. The aim of this study was to determine differences in IVM, IVF, and in vitro (IVD) between wool and hair breeds of sheep. A protocol for IVF (Wani 2002 Small Rum. Res. 44, 89-95) was used in wool (W) and hair (H) breeds. A total of 251 W and 251 H ewes were used. The ovaries were obtained after slaughter and transported to the laboratory in physiological saline (25°C). A total of 411 ovaries from W and 440 from H ewes were used, and 805 follicles of W and 790 of H ewes were aspirated. From these, 663 (82%) cumulus-oocyte complexes (COCs) of Wand 597 (76%) of H ewes were obtained and then used for the procedures of IVM, IVF, and IVD. The average number of COCs recovered per ovary was 1.6 forW and 1.4 for H. The average number of follicles per ovary was 1.9 for W and 1.7 for H. For IVM, COCs were incubated in TCM-199 supplemented with 20% serum from estrous ewe (SEE) for 24 h. All incubations were performed at 38.5°C in a humidified atmosphere of 5% CO₂ in air. After this period, COCs were placed in fertilization medium (TALP supplemented with 200¼g/mL heparin, 3¼g/mL penicillamine, and 1¼g/mL hypotaurine). For insemination, frozen-thawed semen from H and W rams was washed by centrifugation in two concentration gradients of a silicone solution. Oocytes and semen from the corresponding breed types were co-incubated for 18 h. For IVD, presumptive zygotes were incubated in SOF medium supplemented with 20% SEE for 7 days. Eight replicates were made. The rates of IVM, IVF, and IVD were analyzed by logistic regression, using as response variables: IVM, IVF, and IVD results, and as independent variables: breed and replicate. The percentage of recovered oocytes was 82% for W and 76% for H. For IVM and IVF, the recovered oocytes produced 535 fertilized oocytes of W and 446 of H. From these, 81% of the W oocytes and 75% of H were fertilized. Oocytes from W showed a higher percentage of IVM and IVF, with a statistically significant difference (P < 0.05). The percentage of division was 63% for W (n = 419) and 52% for H (n = 312). There were no statistically significant differences between the two groups for embryo IVD (P > 0.05). No statistical differences were found between replicates and no interactions were observed for breed × replicate (P > 0.05). It is concluded that IVM, IVF, and IVD procedures used for the development of embryos in W ewes can be used with similar results in H ewes. This is the first report of sheep IVF in Mexico that provides relevant information about the procedures of IVM, IVF, and IVD in hair and wool sheep, andsets a precedent for future investigations on in vitro embryo production in haired sheep breeds in Mexico.

Funding for E.A. Ordóñez-León was provided by CONACYT and UNAM.