Written by Christina Mogck under the direction and review of George Perry.
Proper semen handling techniques have a big impact on overall success in an artificial insemination program. Small mistakes in thawing semen can have detrimental effects to the sperm including decreased percentage progressive and overall motility. The recommended thawing method for a straw of frozen semen is using a warm water bath at 96⁰F for 45 seconds. Another method that is currently used is called pocket thawing. Pocket thawing is where a semen straw is warmed by body heat or a warm AI gun.
Conception Study: Pocket thawing vs. warm water bath
Recent studies have shown differences in conception rates when comparing pocket thawing to utilizing a warm water bath. A recent study conducted in dairy cattle evaluated the differences between pocket thawing and using a warm water bath. This experiment considered different semen extenders (egg yolk citrate or heated whole milk), different sires, and different methods of thawing on conception rates in 475 Holstein cows. The two methods evaluated were: 1) a warm water bath was set at 96⁰F and the straw left to thaw for 45 seconds as recommended by most bovine AI organizations within the United States, or 2) removing the straw from liquid nitrogen, wiping it off with a paper towel and then placing the straw into the AI gun (pocket thawing). Each cow was visually detected in estrus before being inseminated and were allocated to a treatment based on sire, extender, and thaw method. Results indicated that conception rates were influenced by both sire and thaw method but not on the type of extender used. Therefore, the success of the pocket thawing technique was dependent on sire and not the extender. Some sires showed no difference in conception rates between thawing methods and others had significant differences. Since some sires can be negatively affected by pocket thawing, this thawing procedure should be tailored specifically for individual sires (DeJarnette, 2005).
Other Pocket Thawing Methods
Another recent study used a different pocket thawing method where the frozen straw was wrapped in a paper towel and placed in a thermally protected pocket for two to three minutes before being loading into the warm AI gun. They compared this method of pocket thaw to the conventional warm water bath method in four dairy heifer herds. They also found that conception rates were influenced by herd, sire, straw size, and inseminator, but thawing method did not impact conception rates. Thus if semen is prepared specific for the pocket thawing method and bulls that are known to be successful in this method, there were no differences in conception rates (Kaptroth, 2005).
In conclusion, straws should always be thawed by the recommendations of the AI company that has processed them. Since small mistakes in semen handling can have big impacts on the success of an artificial insemination program. The pocket thawing method can be successful if the semen straw is prepared specifically for pocket thawing. Thus, producers must be aware that not all sires can be used for pocket thawing and the effect of pocket thawing a straw of semen not recommended for this method can lead to a large decrease in conception rates. The warm water bath method is still the safest method for thawing frozen straws if the producer is unsure on the method of thaw specific for a straw.
- DeJarnette, J., Marshall, C. (2005). Straw-thawing method interactions with sire and extender to influence sperm motility and conception rates of dairy cows. Journal of Dairy Science. 88(11), 3868-3875.
- Kaproth, M., Rycroft, H., et al. (2005). Effect of semen thaw method on conception rate in dairy heifer herds. Reproduction, Fertility and Development. 17, 157-158.