It can also adversely affect the growth rates of unborn calves and reduce a cow's capacity to make milk by as much as one-third.

But the days of heat stress in the dairy barn are numbered.

Cornell University agricultural engineers have combined the latest technology in keeping cows cool in commercial barns using three tools not previously combined: a time-integrated variable (TIV) environment controller, tunnel ventilation and an evaporative cooling process.

Construction of a pilot barn in St. Lawrence County, N.Y., is scheduled for completion in late July, and milk production is slated to begin Aug. 1. If the cooling project is successful, dairy producers will be able to install the technology in existing structures.

The strength of the system is that it is automatic, says research engineer Curt A. Gooch, dairy facilities specialist for Cornell's PRO-Dairy Program with the Department of Biological and Environmental Engineering. Gooch worked on the pilot project with Michael B. Timmons, Cornell professor of Biological and Environmental Engineering.

"This system assesses the barn environment and runs the systems automatically," says Gooch.

The brain behind the ventilation system is the TIV, which commands both the ventilation and cooling systems in the barn. Like a computerized thermostat, the controller accounts for the barn's air temperature and the target temperature set by the barn manager.

Unlike a thermostat, the TIV assesses the barn's inside temperature for a 12-hour rolling temperature average. It also calculates and maintains a running record of the average temperature inside the barn for the previous 24 hours.

When controller sensors register cow heat stress at around 70 degrees Fahrenheit, the TIV turns on a bank of large fans and, if necessary, the barn's evaporative-cooling equipment. The fan's tunnel-effect ventilation and the evaporative cooling system remove the accumulated heat, thus cooling the cows.

Inside a free-stall barn that can house around 200 cows, the system moves the air quickly at about 500 to 600 feet per minute. But for the engineers, there is a problem to overcome: the cows themselves.

"Air acts like water in a creek in many ways. The cows act like boulders in a creek," says engineer Gooch. "Once the moving air gets to the cow, the air stops and the movement dissipates. That's a problem, and that's why the velocity of the tunnel ventilation must be so great."

Tunnel ventilation, an agricultural concept once found exclusively in poultry and swine farms, has made its way to the dairy industry. Poultry and swine producers have found that increased animal comfort during the summer can reap economic benefits if the tunnel ventilation system is designed, installed and managed properly, says Gooch.

"The application of tunnel ventilation as a summertime system in the dairy industry is relatively new," he says.

Older-style barns without effective summertime ventilation or wind exposure use axial-flow fans along feed barrier and resting areas. But these fans merely move air within the barn and do not provide air exchange, says Gooch.

With tunnel ventilation, fans on one gable draw air from inside the barn and push it outside, while vents, called inlets, on the barn's opposite gable pull fresh air into the barn.

On very hot days, ventilation needs to be supplemented by an evaporative cooling system as air conditioning is too costly for dairy facilities. The cooling system works much like the human body, expelling moisture on hot days to cool itself.

In the barn, water is discharged by small nozzles at a high pressure into fast-moving air, lowering the temperature inside the barn by about 10 degrees Fahrenheit, says Gooch.

"This technology is innovative and here for producers to try," says Gooch. "The cost of a TIV controller is only slightly more than conventional stage controllers, but it offers better management of the barn environment during hot, summer conditions." - By Blaine P. Friedlander, Jr.

[Contact: Blaine P. Friedlander Jr.]

26-Jul-2001