Influência do tempo na fertilidade do sêmen descongelado de garanhões da raça Quarto de Milha

Abstract

When it comes to reproduction biotechnologies, it is known that the fertility index of equine frozen semen is still reduced, since the freezing and thawing processes lead to deleterious effects on the spermatozoon, decreasing its rate of motility and vigor, modifying its morphology and, consequently, reducing the reproductive potential of the breeders. Therefore, the need for in vitro tests to assess the quality of thawed equine semen, as well as its in vivo viability, taking into account the possible influence of the individuality of the animal on the way sperm cells behave in the face of freezing processes. and thawing. Therefore, the objective of the present study was to evaluate in vitro seminal quality parameters of different stallions during the thermoresistance test, with the purpose of obtaining a technique with greater repeatability, and that helps to increase the results in the use of equine frozen semen. For this, semen samples of 4 Quarter Horse stallions were used, in 5 repetitions, submitted to TTR at times 0, 30, 60 and 90 minutes. Sperm kinetics was evaluated using CASA. Membrane integrity was evaluated by double staining (Carboxyfluorescein Diacetate and Propidium Iodide), and acrosome integrity, Fluorescein Isothiocyanide conjugated to Peanut agglutin. Sperm morphology was analyzed by wet chamber microscopy with phase contrast microscope. In vivo viability was tested by inseminating 10 mares for pregnancy or collecting embryos distributed among the breeders. Data were analyzed using the Statistical Analysis System (SAS), with mixed linearity and plots repeated over time, adopting autoregressive covariance; and means compared by the Tukey Kramer test. Correlations between variables were assessed using Spearman's correlation coefficient. A significant interaction was observed in the parameters sire, time and sire x time interaction (p < 0.001) in sperm kinetics, indicating individuality among stallions in terms of sperm longevity. This individuality was repeated in membrane integrity, where only one of the stallions maintained an intact membrane without significant difference up to 90 minutes post-TTR, while the other stallions had differences in membrane integrity at 30 and 60 minutes, respectively. There was no difference in sperm pathology or acrosome integrity between times or sires. 50% of the inseminated mares had an embryo or pregnancy and all seminal samples had at least 1 pregnant mare or embryos. Clearly demonstrating the individuality of the breeders and the need for more knowledge of their seminal characteristics of sperm longevity, in order to standardize AI protocols in order to determine the most appropriate moment for insemination according to the time of ovulation, keeping better fertility rates.