Cows that experience heat stress during their dry period produce less milk, are more prone to disease, and are more difficult to breed back than cows that do not suffer from heat stress just prior to calving. These negative impacts of heat stress on cows are well known. But what about the calves these cows are carrying?

In the April 2013 issue of Penn State's Dairy Digest, Coleen Jones, research associate, discusses a recent study conducted at the University of Florida that offers some new insight on calves born to cows that experienced heat stress during the dry period. The study was published in the December 2012 issue of the Journal of Dairy Science.

Some important findings include:

  • Calves born to heat-stressed dams weighed 13 pounds less at birth and 28 pounds less at weaning than calves born to dams with access to cooling.
  • Colostrum IgG content was not affected by heat stress. However, calves born to heat-stressed dams were less efficient in absorbing IgG from colostrum and had lower serum IgG concentrations for the first 28 days of life than calves born to cooled cows.
  • Calves exposed to heat stress before birth also had a compromised T-cell response, as measured by the number of monocytes in circulation at 7, 28, 42, and 56 days of age.

"These results confirm that calf body weight can be significantly impacted by heat stress during the final weeks of gestation," Jones says. "In addition, both passive transfer and cell-mediated immunity were compromised in calves exposed to heat stress."

With summer just around the corner, now is the time to evaluate your cooling strategies. Don’t forget about your dry cows!

More in Heat Stress during the Dry Period Affects Calves Too

Source: Penn State Dairy Digest April 2013