COLLEGE STATION – 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.
The calf hutches are free-standing polyethylene structures resembling oversized dog houses.
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.”
“Additional study showed that in areas of water shortage, using water to cool heifers might not be the best use of this valuable resource,” Jordan said. “Unless heifers are moved out of their hutches for treatment, bedding becomes wet and a disease reservoir. And constructing permanent shades over hutches removes one of the key benefits of the hutches, which is to move them to ‘clean’ ground after each calf is raised. Plus, a permanent shade might be detrimental in the winter, when the sun’s rays help warm the calf.”
Friend said over the years the researchers have tested many different reflective films, including some laminates that were made to military specifications. But some of the most expensive material tested still could not last 60 to 90 days in the Texas sun without delaminating.
In the last year, he and his collaborators successfully identified a reflective material that is inexpensive, easily lasted from two to three months in the scorching Texas sun, and remained on the hutches until the calves were weaned and removed.
Study data showed interior ceiling temperatures in hutches with reflective covers were about 25 degrees lower than the control hutches used in the study at 10:30 a.m. and about 30 degrees lower at 2 p.m. on summer days.
“This large difference certainly influences the comfort of calves that seek shade within the hutches during periods when there is little wind. Over 10 days of on-farm trials, the highest daily peak temperatures at the level of a lying calf were 8.46 degrees lower in the hutches with reflective covers,” Friend said.
He said ambient and interior temperatures from covered and control polyethylene calf hutches over a 48-hour period showed cooler temperatures in the insulated hutches during the hottest time of the day, and the warmer temperatures during the night indicated the reflective insulation was useful during both hot, sunny days and cool nights.
“The design of covers from the fabrication process to the material and the mounting system is continuing to improve, and testing of the latest material and mounting system is now underway on several cooperating farms,” Jordan added. So the team’s goal of “developing a useful reflective cover that costs under $4 per hutch and lasts up to 90 days” is now within reach.
While the cover will be disposable, the bungees and PVC pipe required to attach the material to the hutch will be reusable, Friend said.
“This would provide Texas dairy producers with an effective and inexpensive way to lower heifer body temperature and, by extension, improve animal well-being and productivity,” Jordan said.
Friend, who is also investigating whether the calf’s immune function is improved by using the hutch covers, said dairy producers could adopt the study’s results very quickly.
“The key to keeping the costs down is ordering the covers in large numbers because there are huge savings in costs,” he said.
While Friend said farmers always have to watch their costs, there is yet another issue that could influence accessibility to markets for a farm’s milk.
“Farm animal welfare audits are becoming increasingly important,” he said. “And some audits are starting to insist the calves have adequate shade, so auditors are likely not to consider an uninsulated plastic hutch to be adequate shade for the animal.”
As drought and hot temperature conditions continue in the Southwest, there’s the potential for wide adoption among dairy producers, Friend said.
“It certainly could help in the Southwest. In addition to conducting some trials this summer in Texas, we will also be working with a farm in southern Arizona. I am very excited to see how much reflective covers can help in that environment.”