This summer's intense heat wave came to Arkansas in June, a few weeks earlier than usual, and could possibly stay around through the typical August stretch of high temperatures. Although heat waves are always a major challenge for poultry producers, Arkansas has not recorded any significant losses of poultry from heat-related causes this summer. This year's early onset of heat could have a silver lining to it by giving the birds at an early age an opportunity to become acclimated to a long, hot summer.
If a sudden heat wave hits in the early spring, baby chicks have not had a chance to become accustomed to rising temperatures, explained Robert Wideman, a poultry physiologist and associate director of the Center for Excellence in Poultry Science at the University of Arkansas Division of Agriculture. He said Israeli researchers found that exposing baby chicks to their first round of heat stress caused them to pant and spread their wings. The stress didn't kill them by the time temperatures dropped back to normal. When the next heat wave hit, the birds were more resistant to the higher temperatures and better able to survive.
By the time the birds are five or six weeks old, Wideman said, "their hearts literally haven't learned to pump enough blood to the periphery of their skin to dissipate heat. That's when you typically see a lot of birds die."
An earlier exposure to the heat, such as they've been getting in Arkansas in recent weeks, means that they might not achieve as high a growth performance level as desired, but they're becoming more tolerant of the heat and better able to survive than they would if the first blast of sustained high temperatures happened later in the summer. It's better that the younger, more adaptable and agile birds experience the heat at that age because the chickens need all the help they can get.
"The modern broiler is basically a big couch potato," Wideman said. "It's bred to eat, drink and sit down."
Without sufficient acclimation to the heat, the big bird is at a disadvantage because it hasn't spent much time panting, pumping more blood and exercising its heart. "If the heart has been weak and suddenly you have a heat stress challenge, it has a world of trouble," Wideman said.
The poultry industry has been revamping houses for growing chickens with cooling ventilation in mind. The trend in the past 20 years has been toward poultry processing companies encouraging their growers to build houses with tunnel ventilation, Wideman said, "which is basically where you create a high velocity of air flow down the length of the house." A house might be 500 feet long and 50 feet wide with banks of 48- and 52-inch fans at one end creating negative pressure on the inside of the house and inlets with cool cells at the other end pulling air through a cool pad.
"That's been a godsend to producers simply because you can grow birds during the summer and get performance out of them by using tunnel ventilation to cool the house down," Wideman said. "They've supplemented that in some places with misting systems of nozzles at various intervals spraying a fine aerosol mist into that windstream."
Susan Watkins, a UA poultry extension specialist, said the broiler industry's investment in the tunnel ventilation facilities has helped keep birds comfortable during intense heat.
"We may not keep the temperature ideal and we will lose some performance, particularly on the 6-plus-pound market weight birds, but the days of massive heat loss mortality are no longer a devastation for the industry," Watkins said. The turkey industry faces more challenges because its production facilities still use the curtain-sided barns with fans and foggers used to cool its birds.
Regardless of the specific summer weather pattern or the type of house, poultry growers face some constant realities: it gets hottest late in the afternoon, the heat dissipates after dusk and conditions become cooler at night. The birds notice this and wait until later in the night to start eating once they've dissipated some of the day's body heat. If the heat spell lingers and nights don't cool down much, the birds drink more water, eat less or not at all and don't grow.
These are presumed to be the potential conditions as long as the electricity stays on. If a power failure hits during peak summer usage, problems follow. Birds must be kept alive by providing them the right water balance, temperature and humidity.
"A grower is challenged just to make sure your generators are ready to go because if you have a power failure and can't move air across those birds, you're in big trouble," Wideman said. "You can't have your well go dry. You can't have your evaporative cooling pads or your misters go dry."
Research has shown that modifying birds' nutritional diet has only a minimal effect on their ability to feel cooler and survive the summer. A better option is to formulate a diet that causes the birds to drink more water, Wideman noted, because survival of heat stress is about water balance. Birds die when they go into circulatory shock after water depletion causes their blood volume to decrease.
"Physiologists studied heat stress in birds and it turned out that anything you can do to cause them to drink more water will help them survive heat stress," he said. Adding electrolytes to water causes them to want to drink more.
Wideman emphasized that specific situations vary among growers. For example, modifying feed to encourage poultry to drink more can cause them to excrete more water onto the litter, which can cause problems on the pads of the chickens' feet. Wideman said growers should always consult their company representatives to determine the best plan of action to accommodate their birds' nutritional and cooling needs in hot weather.
This article is from the University of Arkansas Division of Agriculture Communications Department.