SHEEP EMBRYOS VITRIFIED USING A “ONE STEP” TECHNIQUE PRODUCED IN TWO SEASONS

Abstract

Objective: Vitrified ovine embryos produced in two seasons by a “one step” technique, and verify its viability at thawing and its post-transference fertility.
Desing/methodology/approach: Estrus was synchronized in 16 pelibuey ewes, eight per station, by vaginal sponges and superovulated with FSHp. Sponges were removed on 13th day and since his removed, at 56±1 hours females were mated by male, and finally on seventh day the embryos were collected. The collected embryos were selected for “one step”
vitrification, submerged for ten minutes in 1.5 M Ethylene Glycol (EG)+0.2 M sucrose in TCM 199; embryos were loaded into straws and immersed in liquid nitrogen. Sixteen straws for each season were thawing. Embryos were evaluated their viability by Hoechst testing vital cell staining, was observed in epifluorescence microscope. The viability, embryo quality and fertility was analyzed by test X².
Results: There was no differences (P>0.05) between embryo viability 50 and 68.75%, the value of the morphological classification 2.43±0.60 vs. 3.31±0.58 and the percentage of live cells 49.37 vs. 53.75% for spring and autumn, respectively.
Study limitations/implications: Fertility per season was 58.3 y 66.6 % (P>0.05) for spring and autumn, respectively.
Findings/conclusions: EG as a cryoprotectant is recommended in the use of a “one step” technique, obtaining an average of 59.3% embryo viability, regardless of the reproductive seasonality in superovulated tropical sheep.