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ABSTRACT

O sêmen de garanhões mostra diferenças individuais com relação a sua preservação. Apesar das causas ainda não estarem claras, fenômenos que ocorrem durante manipulação e armazenagem do sêmen a +5°C exercem considerável influência sobre a funcionalidade e integridade da membrana plasmática do espermatozóide eqüino. O presente trabalho objetivou avaliar a eficácia da adição de diferentes diluentes de sêmen sobre a motilidade progressiva, manutenção da funcionalidade e integridade da membrana plasmática do espermatozóide eqüino preservado a +5°C por 72 horas, bem como sobre a taxa de fertilidade. Pode-se concluir que a avaliação da integridade e funcionalidade da membrana espermática oferece informações úteis à análise de rotina do sêmen eqüino que podem auxiliar na. previsão da fertilidade do sêmen resfriado.

The aim of this study was to improve the quality of frozen-thawed equine sperm by the addition of caffeine to it. Semen from nine stallions was frozen and different concentrations of caffeine (3, 5 and 7.5 mM) were added to frozen-thawed semen. The sperm kinetic parameters, membrane functionality and integrity, and acrosome integrity and spontaneous acrosome reacted sperm were evaluated with a computerassisted sperm analysis, a hypoosmotic swelling test and epifluorescent microscopy, respectively. Nitrite and hydroperoxide concentrations of frozen-thawed semen were measured using spectrophotometry. Sperm fertility was evaluated by artificial insemination (AI) of 16 mares with thawed ejaculates (control and 5 mM caffeinetreated groups). Compared to that in the control, the addition of 5 mM caffeine induced an increase in sperm motility (38.9 ± 2.8 versus 32.6 ± 3.4%), and a decrease in nitrite concentration (11.4 ± 2.1 versus 12.8 ± 2.9 µM/µg protein, p < .05). Moreover, the pregnancy rate from AI in the caffeine group was significantly higher (62.5%) than that in the control group (12.5%). These data suggest that caffeine reduced the nitrite concentration and enhanced sperm motility in thawed equine sperm, thus increasing the fertility rate in mares inseminated with caffeine-treated equine semen.

Many high-performance stallions have low-quality frozen semen.Thus, strategies to improve the quality of post-thawed semen before artificial insemination are of great interest to increase the fertility of those animals. During the semen freezing process, equine spermatozoa are more prone to oxidative stress because a large portion of the seminal plasma is discarded after centrifugation (Brinsko et al., 2000). This results in an imbalance in seminal plasma antioxidants, reactive oxygen (ROS) and nitrogen species (RNS) produced mainly via sperm metabolism (Amidi et al., 2016). Equine sperm mainly relies on oxidative phosphorylation for the production of adenosine triphosphate (ATP;Gibb et al., 2014) that may lead to high oxidative stress than that in the human sperm, which depend on glycolysis as the main energy production pathway (Aitken & Drevet, 2020;Mayorga-Torres et al., 2017). Moreover, nitric oxide (NO) and peroxynitrite anions, which are nitrogen-derived free radical, likely play significant roles in reproduction and fertilization. However, the