114 INFLUENCE OF COOLING TIME IN THE VIABILITY OF POST-THAW RAM SEMEN

Abstract

The objective of the present experiment was evaluated the influence of different cooling time in the viability of post-thaw ram semen. The experiment was conducted in Umuarama, Paraná, Brazil. A pool of 9 ejaculates from Saint Inês rams was analyzed. Motility (mot, in percent), vigor (vig, in percent), and concentration were evaluated. The samples were diluted in Tris-egg-yolk extender, in an insemination dose of 30 million spermatozoa/mL. The straws were taken into a refrigerator for cooling in 5°C. The tested times of cooling were 1 h (T1), 2 h (T2), 3 h (T3), 4 h (T4), and 5 h (T5). After each one of these periods, motility and vigor were evaluated and the semen were freezing in a polystyrene container with liquid nitrogen. After 10 days, the straws were thawed, motility and vigor were evaluated again, and the samples were submitted to thermo-resistence test. The results were analyzed by Proc GLM of SAS software (SAS Institute, version 8.0, Cary, NC, USA). For fresh semen, the motility and vigor were 78.89 ± 8.75 and 4.00 ± 0.47, respectively. After cooling, the results were mot T1 (47.78 ± 10.30), vig T1 (3.00 ± 0.00); mot T2 (45.56 ± 8.31); vig T2 (2.67 ± 0.47); mot T3 (45.56 ± 14.23), vig T3 (2.78 ± 0.42), mot T4 (53.33 ± 9.43), vig T4 (3.11 ± 0.31), mot T5 (45.56 ± 13.43), vig T5 (2.78 ± 0.63). For thermo-resistance test, the results of each cooling time were T1 motility = 14.44 ± 11.65; T1 vigor = 1.78 ± 1.03; T2 motility = 16.67 ± 9.43; T2 vigor = 2.22 ± 0.92; T3 motility = 23.33 ± 9.43; T3 vigor = 2.33 ± 0.47); T4 motility = 26.67 ± 8.16; T4 vigor = 2.78 ± 0.42; T5 motility = 27.78 ± 7.86; T5 vigor = 2.56 ± 0.50). There were no statistical differences for the cooling time results of motility, vigor and thermo-resistance test (P < 0.05). In the conditions of this research, the cooling time had no influence in the post-thaw viability.