Pre-freezing cooling and sheep seminal viability

Abstract

It was evaluated in ovine semen pool, different cooling times (C) pre-freezing on the motility (M) and the sperm vigor (V) after thawing and TRT (Thermo Resistance Test). Four Santa Ines sheep were submitted to semen collections in nine replicates. After analysis and confirmation of the desirable semen characteristics of each ejaculate, a pool of the ejaculates of the four animals, diluted in modified Tris-yolk, was aliquoted into vales cooled for zero, one, two, three, four and five hours pre-freezing, frozen and thawed. M and V spermatozoa were evaluated, before and after C, and after thawing, when TRT was also performed. The data were compared by Tukey's test. There was a decrease in the M and V of the seminal pool after one to five hours of C before freezing, and the C time did not change these parameters. The thawed sperm pool showed higher M and V after four hours of C when compared to one hour of C before freezing. However, no difference was observed in these parameters when subjected to one, two, three or five hours of C before freezing. M and V were observed in the seminal pool cooled for two to five hours before freezing. The thawed semen, submitted to TRT, presented similar M and V, regardless of the C time before freezing. It was concluded that C for four hours pre-freezing provides better M and V post-thawing, while C for two to five hours generates seminal pattern acceptable by TRT.