EFFECT OF EQUILIBRATION TIME AT 5 °C AND PHOTOPERIOD ON SURVIVAL OF RAM SPERMATOZOA FROZEN IN STRAWS

Abstract

The effect of various equilibration times at 5 °C on the cryosurvival of ram spermatozoa frozen in 0.5-mL straws was assessed for semen collected during decreasing and increasing photoperiods. The percentage and rate of forward progression of motile spermatozoa increased significantly from 0 to 2 h equilibration, remained constant from 2 to 6 h and decreased significantly at 18 h. Kinetic rating of motile spermatozoa changed similarly. Photoperiod has a significant (P < 0.01) effect on survival of spermatozoa at all equilibration times, but rate of forward progression was affected only at the 0 h equilibration time. Key words: Spermatozoa survival, equilibration time, frozen-thawed semen, rams