November 10, 2022 at 4:39 p.m.
That was a topic of discussion at the Professional Dairy Producers Calf Care Connection workshop Oct. 25 at Dutch Dairy in Thorp.
The Dairyland Initiative outreach specialist Courtney Halbach was on hand to discuss all things ventilation. Halbach works with the University of Wisconsin’s School of Veterinary Medicine to help provide resources and support to dairy farmers throughout the state.
“Ventilation means that fresh air is being provided into a building space,” Halbach said.
Rather than simply moving air, the air from inside a building is actually exchanged with fresh air coming from outside. That fresh air displaces heat, moisture, noxious gases and airborne pathogens.
During cold weather, air should be exchanged a minimum of four times each hour,” Halbach said. “As the temperatures go up, the ventilation rate needs to go up as well.”
Halbach said often times ventilation gets blamed for causing problems that have grown from other sources.
“I get a lot of questions about issues with respiratory disease in calf barns, and people say they think ventilation is to blame,” she said. “Yes, ventilation can sometimes be to blame, but there are a lot of different aspects to look at in calf management.”
Halbach referenced a troubleshooting list created by her colleague Dr. Teri Ollivett which, in order of priority, looks at the stocking density or space per calf; failure of passive transfer; hygiene and bedding management; feeding rates and consistency; accurate and early disease detection; ventilation and finally vaccination.
“I argue that stocking density has a huge effect on air quality and how well the ventilation system is working,” Halbach said. “Before I even start to assess a ventilation system, I am looking at how many calves are in the barn.”
Halbach said the outer limits of stocking density are often pushed too far.
“I know it is so easy when you see an open space to put a calf in the barn,” Halbach said. “But when you add that calf to the facility, you are contaminating the air more; there is increased bacteria and moisture in the air. You also are affecting hygiene. As you put more calves in, the space starts to get dirtier.”
Stocking density can be measured from several points of view. Halbach said stocking density can mean the total barn volume but can also refer to the amount of space each calf has to lie down in. Halbach said a good rule to follow is to allow at least 35 square feet of bedded pack space or resting area per calf until the weaning period.
“The more room, the better,” she said. “If you were to double the stocking density of a barn, you would have to increase the ventilation 10-fold in order to keep an equivalent air quality as a properly stocked barn. When it is zero degrees out, do you want to be ventilating a barn at four air exchanges per hour or 40?”
The challenges of ventilating a calf barn begin when the barn is enclosed to help provide a comfortable environment for the caregiver.
“I wouldn’t be afraid of the cold,” Halbach said. “I wouldn’t try to make a calf barn warm. We don’t want to add heat to the building; all that does is create a nice environment for the bad bacteria to grow. I am OK with cold barns.”
Instead of warming the barn, Halbach looks at means, such as nutrition and bedding, to keep calves thriving.
Halbach said the thermoneutral zone of a newborn calf is in the range of 50 to 78 degrees. As calves grow, they become more tolerant of cold and their thermoneutral zone drops to the range of 32 to 73 degrees.
“In their thermoneutral zone, calves do not have to expend extra energy warming or cooling themselves,” Halbach said. “One way we can help keep them comfortable is to give them a nice, deep place to rest.”
Halbach said a system of nesting scores are used to evaluate the bedding pack available to calves. A nesting score of one means that when a calf is laying down, the legs are entirely visible with no bedding covering them up. Use of sawdust and corn stalks typically result is a nesting score of one. A nesting score of two means that the legs are partially visible while the calf is laying down; meanwhile, a score of three means the legs are generally not visible.
When it comes to creating a deep nest for calves, Halbach said long straw is the gold standard over a gravel floor or concrete sloped to a drain. Allowing urine to leave the building is important to keep the bed from becoming wet and filled with ammonia gas.
Using wood shavings as a bed keeps the urine from running out of concrete-based pens, but they create a wet base and a build-up of ammonia. Pens bedded with a shaving base need to be cleaned frequently.
The design of individual pens can also play a factor in air quality.
“Individual pens are a microenvironment,” Halbach said. “We have to figure out how to ventilate them without creating a draft on the calf.”
Creating that balancing act can be a challenge, Halbach said. While solid partitions between calves limit calf-to-calf contact, they also limit airflow; the opposite is true of wire panel dividers. Halbach said the happy medium is to have solid panels between calves and use open wire panels to create the front and rear boundaries of the pen.
“There are many things that play into creating the best environment to raise calves,” Halbach said. “But stocking density, ventilation and sanitation all play key roles.”
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