RESEARCHERS from the animal science department at Texas A&M University's College of Agriculture & 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, an AgriLife Extension dairy specialist based in Dallas, Texas. "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 death rates, 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. "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, they collected preliminary data on the interior air temperature of the calf hutches, which reached 113-117 degrees F during clear days when ambient temperatures were 97-104 degrees F. They concluded that 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% 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. An 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, the researchers found that 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. However, he said some of the most expensive material tested still could not last 60-90 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.
The study data showed that interior ceiling temperatures in the hutches with reflective covers were about 25 degrees F lower than the control hutches at 10:30 a.m. and about 30 degrees F 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," Friend said.
He said ambient and interior temperatures from the 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 that 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 (polyvinyl chloride) 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 their decision on the hutch covers.
"Farm animal welfare audits are becoming increasingly important," he said. "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," he said.
Managing heat stress
With hot summer weather approaching, Dr. Robert Collier, a professor at the University of Arizona Agricultural Research Center, reminded dairy producers about the importance of managing dairy cattle to minimize the negative impacts of heat stress that may inhibit immune function, thus hampering their health and productivity.
"Heat stress is a health and economic issue in every dairy-producing area of the world," Collier said at a pre-conference symposium sponsored by Prince Agri Products Inc. at the recent Florida Ruminant Nutrition Symposium. "Production, reproduction and animal health are all impaired by hyperthermia. During heat stress, respiration rates and body temperature increase, while feed intake, milk yield and reproduction decrease."
Collier said heat-stressed dairy cows may experience increased levels of the stress hormone cortisol, which can weaken their natural immune system and make them more susceptible to disease and infection.
"High somatic cell counts and a high incidence of clinical mastitis are associated with the hot summer months," he said.
Collier noted that decreased milk production is linked, in part, to reduced feed intake, as well as metabolic changes, during extremely hot, humid weather.
"In heat-stressed dairy animals, an increased metabolic rate causes a reduction in the metabolizable energy that is available for milk production," he explained.
Collier also summarized results of a recent heat stress research project at the University of Arizona that involved feeding an immune-boosting nutritional supplement (OmniGen-AF) to Holstein cows housed in controlled environments. Animals that received the nutritional supplement had significantly greater dry matter intake, reduced respiration rates and lower rectal temperatures during heat stress compared to control cows. They also had lower somatic cell counts after heat stress during the recovery period.
In addition to supporting immune function, dairy experts recommend diet modifications for managing heat stress, such as adding supplemental sources of fat or utilizing lower-fiber feedstuffs to help reduce the heat of digestion. They also encourage producers to provide an adequate source of cool, fresh water, adequate shade, air movement and sprinklers to promote cow comfort and help animals better tolerate a hot environment.
Inoculants are effective silage management tools, but for producers receiving product information from numerous companies, it can often be challenging to select the right product.
Using the right inoculant as part of an overall good silage management program will help producers have high-quality silages. Choosing the correct inoculant is important since the wrong choice can feel like a wasted investment, at best.
"I always recommend that producers ensure there is independent, scientific research for the specific inoculant in the target crop," said Dr. Bob Charley, forage products manager for Lallemand Animal Nutrition. "The trials should validate the efficiency of the product at the application rate on the label and, ideally, be published in a reputable journal or presented at a scientific conference."
Next, Charley said producers should read the product label to look for key items, such as:
* An application rate of 100,000 colony forming units or greater for front-end fermentation inoculants — the minimum level recognized by university researchers;
* If the product contains enzymes, which will aid bacteria in driving a rapid, efficient fermentation, and
* The recommended shelf life and storage conditions.
In addition to these criteria, Charley said producers should evaluate the manufacturing and packaging for clues about the product's future efficacy.
"Using an inoculant from a primary manufacturer can help guarantee the manufacturing quality of the product," he noted. "The packaging format and conditions in which the product is packaged are critical to inoculants as they are live, viable organisms that can be killed if exposed to heat, moisture or air."
Industry-standard packaging that helps prevent degradation includes: high-barrier outer packaging (e.g., laminated packets with a foil layer), using nitrogen flushing during packaging to minimize oxygen and preservation agents like moisture scavengers in the formulation.
"Even if you rarely encounter spoilage in your forage, proven inoculants are recommended for all situations," Charley said. "There are always dry matter savings to be realized, and producers need a product that is independently proven to provide a return on your inoculant investment."