click image to zoomTexas A&M AgriLife Researchers from the animal science department at Texas A&M University’s College of Agriculture and Life Sciences and the Texas A&M AgriLife Extension Service have been studying how to improve the comfort and production of dairy cows and calves during sweltering summer months.
“The effects of summer heat and humidity on dairy cows in Texas and elsewhere have been well documented, with losses in milk production, dry matter intake and reproduction,” said Dr. Ellen Jordan, AgriLife Extension dairy specialist, Dallas. “We have been looking into how we might improve animal comfort and well-being through reducing summer heat stress, thereby mitigating performance losses.”
Dr. Ted Friend, a professor in the college’s department of animal science, said since the 1950s, research has shown that calves subjected to heat stress have subpar performance, including increased deaths, reduced growth rates, impaired immunity, reduced feed intake, decreased feed efficiency, increased respiratory rates and increased rectal temperatures.
“When dry cows are cooled, their calves are heavier and they produce more milk,” Friend said. “And as dairy calves are far smaller than their dams, the question becomes: Do calves also need cooling to beat summertime heat and, if so, how can we provide economical cooling and still ensure their health?”
To find out, Friend and collaborators from the animal science department conducted a long-term study at two Texas dairies to determine how calf hutches might be best positioned and used to reduce heat stress on calves.
In 2007, Friend and others collected preliminary data on interior air temperature of the calf hutches. The interior air temperature reached 113 to 117 degrees during clear days when ambient temperatures were 97 to 104 degrees. They concluded the elevation in interior temperature was due to radiant heat absorption.
Following this preliminary data collection, the researchers experimented with placing hutches and their outside pens under 80 percent shade cloth, which others had shown improved calf comfort.
“However, the lack of sunshine raised concerns about increased moisture in the hutch and yard, as well as increased bacterial contamination,” Jordan said. “Sunshine has long been known to be very effective in controlling many pathogens, and that advantage is lost when moving calves indoors.”
To maintain the benefits of sunshine, while improving the quality of shade within plastic hutches, the group experimented with a range of reflective films and materials in 2008. Insulating material tested on farms in 2007 and 2008 significantly lowered temperatures in the hutches during the hottest time of the day and increased temperatures in the hutches during cold periods. However, researchers found the material used was “bulky, fragile and not very practical.”