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Refreezing techniques allow other treatments to be given to the semen and achieve greater efficiency in animal reproduction, such as performing sexing techniques on previously frozen semen. The objective of this study was to evaluate the effect of the refreezing of bovine semen on the integrity of the plasma membrane, morphology, viability and individual motility. Semen from three Brahman bulls collected during three occasions (n = 9) was used, each with an electroejaculator. The ejaculates were frozen in liquid nitrogen (-196 ° C) using Triladyl® diluent. Three treatments were analyzed: Fresh Diluted Semen (FDS), Frozen Thawed Semen (FTS) and Frozen Thawed Re-frozen Semen (FTRS). Spermac (Minitube®) stains were applied for morphology, BLOM for viability and the HOST test (cell endosmosis) for plasma membrane integrity. There were significant differences (P≤0.05) between FDS, FTS and FTRS for the individual motility percentages (92.5%, 65.42% and 46.25%), percentage of live sperm (84.18%, 61.70% and 48.21%), percentage of normal sperm (97.60%, 95.97% and 93.46%) and percentage of sperm with positive endosmosis (82.50%, 50.13% and 31.58%) respectively. Under the conditions of this study, the re-freezing process of bovine semen decreases individual motility, viability and affects the integrity of the plasma membrane, however, it can be a viable alternative when applied only to ejaculates that have initially presented an individual motility when fresh ≥ 80%. [ABSTRACT FROM AUTHOR]

The experiment was carried out between January and March 2020 in the animal reproduction laboratory at the University of California, Davis USA. The objective was to evaluate the effect of the presence of the corpus luteum in the aspirated oocytes of ovine female ovaries at different stages of the reproductive cycle, on the parthenogenetic development of embryos in vitro to determine the average number of oocytes collected per ovary, percentage of viability of oocytes, percentages of cleavage and blastocysts in vitro and the efficiency of the procedure. 158 ovaries from sheep from a slaughterhouse were used; mean values of 3.33, 1.24 and 1.52 oocytes / ovary were obtained and the percentages of viability were 100%, 45.87%, and 56.82% for oocytes from ovaries with corpus luteum, ovaries without corpus luteum and ovaries from pregnant females respectively (P ≤0.05); there were no differences (P> 0.05) in the cleavage percentages with values of 72.5%, 72.0%, and 56.0% and in the parthenogenetic blastocysts with values of 37.93%, 44.44%, and 42.86% for oocytes from ovaries with corpus luteum, ovaries without corpus luteum and ovaries of pregnant females respectively, however, the highest production of blastocysts / ovary (P≤0.05) was from ovaries with corpus luteum. It is concluded that the effect of the presence of the corpus luteum in the aspirated oocytes of ovine female ovaries improves the parthenogenetic development of embryos in vitro when evaluating the production of blastocysts per ovary [ABSTRACT FROM AUTHOR]

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