Why, you ask, would you bother with cooling the dry cows in a dairy herd? They are not producing milk; therefore, you don't have to worry about the additional body heat generated in conjunction with milk production. A series of research studies over five consecutive summers conducted at the University of Florida - Gainesville, gives you 10 good reasons. That is an additional 10 lbs of milk produced per head per day in cows cooled during the entire dry period compared to those that were not cooled.
One of those studies shows a difference (lb/day) in milk production of 11 lbs/day through 40 weeks of the subsequent lactation for cows cooled during the dry period vs those not cooled. Cows in each study were dried off an expected 46 days prior to calving and housed in a free stall facility. Cooling was provided by shade, feed lane soakers, and fans for the cooled cow group while non-cooled cows only had shade. After calving, cows from both groups were moved to a lactating cow free stall barn where all were cooled.
Some of the studies also examined calf performance. Results showed calves born to cooled cows have heavier birth weight (+13 lb), weaning weight (+27 lb) and improved immune function compared to those born to heat stressed, non-cooled cows.
The real surprise came when calves from this series of studies matured, calved and entered lactation as heifers. Heifers that were born to cows that were cooled during the dry period produced, on average, 11 lbs/day more milk than those born to dams that were not cooled during their dry period. The message here is that cooling of dry cows not only impacts those cows in their next lactation but also ultimately affects how the offspring perform as they grow, mature and enter lactation. To be most effective, cows must be cooled during the entire dry period. Cooling for only a portion of the dry period, such as the close-up period, showed little response.
But, you say that was Florida - It does not get that hot in Virginia. Results from a recent study monitoring weather patterns throughout the U.S. showed Florida having the most heat stress days (days when temperature-humidity index THI ≥68) at 257 days with Virginia coming in fourth of the top 25 major dairy producing states with 140 days of heat stress days. That equates to approximately 1500 lb per cow loss in milk production in the next lactation for cows experiencing heat stress during their dry period. The study further looked at cost scenarios with several variations in milk price, production response, and facilities investments. That analysis showed investments in soakers and fans or even construction of a new dry cow free stall facility with cow cooling had a very rapid pay off period under most scenarios. If you are looking to continue in the dairy business and make capital improvements in your dairy operation a dry cow facility that provides cow comfort and adequate cooling should be high on your priority list.