The effects of collection and processing procedures on post-thaw bovine spermatozoan characteristics

Thirty-two ejaculates from four Holstein bulls were utilized in the study. Neat semen was diluted (1:10) with 20% egg yolk-citrate and cooled to 5 degrees C within either 0.5 or 3 h, then glycerolated, and equilibrated for 2 h. Straws were frozen over liquid nitrogen, stored at -196 degrees C, and thawed at 46, 37, or 23 degrees C for 12, 20, or 60 sec, respectively. The average percentages of progressive motility and unstained cells post thawing increased (34.5 vs 31.4%; P<0.01 and 41.9 vs 37.1%; P<0.002, respectively) for semen collected in polyethylene rather than in rubber liner-collection cones. The post-thaw mean progressive motility for spermatozoa cooled to 5 degrees C within 3 vs 0.5 h was higher (34.5 vs 31.5%; P<0.0001, respectively). Similar differences were observed for unstained cells (40.7 vs 38.2%; P<0.0001, respectively). Mean acrosomal scores were lower when cells were collected in polyethylene (1.00 vs 1.03; P<0.02) and also when a 3-h cooling period was used (1.01 vs 1.03; P<0.0001). Spermatozoa thawed at higher temperatures exhibited increases (P<0.0001) in both progressive motility and the percentage of unstained cells. The average percentages of progressive motility and unstained cells were 37.1, 35.7 and 26.1% and 43.4, 41.5 and 33.5%, respectively, at thawing temperatures of 46, 37 and 23 degrees C. Based on the results of this study, optimal conditions for bovine semen handling were the collection of semen in polyethylene liner-collection cones, preglycerolation cooling within 3 h, and thawing at 46 degrees C for 12 sec.