Addition of synthetic amino acids in sheep semen improves its quality after cryopreservation / Adição de aminoácidos sintéticos no sêmen ovino melhora a qualidade espermática após a criopreservação do sêmen

RESUMO

Some amino acids can protect mammalian sperm cells against oxidation during thermal stress caused by freezing/thawing. Thus, the objective was to evaluate the protective action of the association of the amino acids L-proline (Pro) and L-glutamine (Glu) against the cryoinjury caused to sheep sperm after cryopreservation. Eight ejaculates were collected from four sheep (n=32) and diluted in Tris-Egg Yolk-Glycerol until the final concentration of 200 x106 sptz/mL and kept in a water bath at 32 °C. The amino acids were added as follows control (without adding amino acids), Pro+Glu 1 (100 M Pro + 500 M Glu), Pro+Glu 2 (300 M Pro + 1000 M Glu), Pro+Glu 3 (500 M Pro + 1500 M Glu) and Pro+Glu 4 (700 M Pro + 2000 M Glu). Afterwards, the semen was cooled to 5 °C for 2 h, after that period, filled in 0.5 mL straws and then placed under liquid nitrogen vapor (N2L), 8 cm from the liquid sheet for 15 min, and then immersed on the N2L. The samples were analyzed for sperm motility, plasma membrane and acrosomal membrane integrity, mitochondrial activity and binding test. The variables were subjected to the normality tests (Lilliefors test) and homoscedasticity tests (Cochran and Bartlett test), afterwards the variables of normal distribution were subjected to analysis of variance and the means compared by the Tukey test with a significance level of 5%. The Pro+Glu 3 group exhibited sp