Research from Iran shows a vast improvement in fertility when heifers received supplemental cooling. During the study, researchers housed Holstein heifers in a shaded structure during July. Upon estrus detection, they assigned heifers to one of three treatment groups:
A control group (Heifers stayed in the shaded structure).
A group cooled with sprinklers from two hours before breeding until two hours after breeding.
A group cooled with both sprinklers and fans from two hours before breeding until two hours after breeding.
All three treatment groups were housed in the shaded structure from two hours after breeding until 45 days post-breeding.
Short-term cooling helped lower body temperature, particularly in heifers exposed to sprinklers and fans. Short-term cooling also improved pregnancy rates. Pregnancy rates were 40% for the sprinkler group and 56.7% for the sprinkler/fan group compared to 23.3% for the control group.
It is desirable to achieve greater than 70% conception rate at first service, according to guidelines in the Gold Standards II. Minimizing heat stress around breeding time can help heifers meet this goal and achieve high pregnancy rates. For additional breeding guidelines, refer to DCHA Gold Standards II.
Always consult with your veterinarian for specific recommendations for your operation.
The research reported in this week's tip originally appeared in the April/May 2011 Akey Dairy Newsletter.