86 MOTILITY AND VIABILITY OF BULL SEMEN DURING 24 HOURS OF STORAGE AT 4°C

Abstract

Currently, cryopreservation process of fresh bull semen is carried out between 3 and 6 hours of refrigeration at 4°C post-collection (Hafez, 1989). However, it is sometimes difficult when the cryopreservation process is not available at the site of collection. The objective of this study was to determine seminal motility and viability in samples maintained at 4°C during 24 hours. A total of 98 ejaculates from 23 adult bulls (Angus, Brangus, Braford and Hereford) were collected and diluted in a semi-defined semen extender (Andromed, Minitüb, Tiefenbach, Germany) and stored at 4°C. Parameters of velocity average path (VAP, µm/s), velocity straight line (VSL, μm/s), amplitude lateral head (ALH, μm), linearity (LIN, %), percentage of rapid cells (RAPID, %), percentage of slow and static cells (SL/ST, %), and viability (VIA, %) were determined by Computer Assisted Semen Analysis (CASA, HTM-ceros 12.1, Berkeley, CA, USA). Measurements were done at 6, 9, 12, and 24 h. The obtained results were analyzed statistically with one-way ANOVA and Dunnet Multiple Comparison Test and are summarized in Table 1. There were no significant differences (P > 0.05) in the VAP, RAPID, or SL/ST during 24 h of storage at 4°C. Measurements were significantly different (P < 0.01) for VSL and VIA at 24 h. Measurements of ALH were increased from 12 h (P < 0.01) and consequently, LIN decreased at the same time (P < 0.01). These results suggest that there are no differences in velocity, except in VSL at the end of the storage time. The type of movement of the spermatozoa change, because ALH increases and the trajectory loses linearity. A decrease in viability suggests that from 24 h of storage, the membrane of the spermatozoa becomes more susceptible. More research needs to be done to evaluate the competence of this time-storage semen in the artificial insemination trial.

Table 1. Parameters of motility and viability of semen maintained at 4°C during 24 h

This research was supported by Centro Genético Bovino de EOLIA S.A.