Effect of Thawing Time on Fertility of Bovine Spermatozoa in French Straws

Thawing times of 9 and 40 s were compared in a 6-mo fertility experiment involving 18,057 first service inseminations to 23 Holstein bulls. Semen extended in Tris-yolk and packaged in . 5-ml French straws was thawed in warm water baths (32 to 35°C) for either 9 or 40 s on alternate days. Based on 75-day nonreturn rates in log-linear models, fertility was significantly higher when semen was thawed for 40 s (66.3%) than for 9 s (64.4%). The improvement with longer thawing was not affected significantly by montli (January through June). Thus, warming of semen in straws to a temperature approaching body temperature provided a slight increase in fertility even during cold weather.