According to Tim Terry, farm strategic planning specialist with Cornell University’s PRO-DAIRY, the calf hutch is still the gold standard for raising calves because it maximizes calf health and performance while minimizing morbidity and mortality.

However, in regions like the Northeast and Great Lakes, winter happens, and for the sake of caregivers, calves are often reared inside rather than in hutches. In moving calves indoors, the challenge becomes trying to duplicate the favorable atmospheric conditions found outside.

This is where the art of ventilation comes in.

Ventilation Requirements

The overall goal of ventilating a calf barn is to get fresh air to and around the calves without creating a draft. “We’re looking for still air, not stagnant air,” Terry said. “Still air is moving at about 60 feet/minute.” That’s equivalent to a normal human exhalation, according to Terry.

This movement of still air displaces the humid, pathogen-laden air that can lead to pneumonia and other respiratory diseases and a general lack of thriftiness that manifests in symptoms such as scruffy, matted hair coats and watery, goopy eyes. Other signs of poor ventilation include the smell of ammonia.

Volatile organic compounds like ammonia are caustic to mucosal tissues which line the nasal passages, trachea and the lungs. Chronic exposure can lead to scarring, which can be permanent and may reduce the animal’s performance for the rest of her life.

Ventilation is necessary for calf health and also the building housing the calves. In winter, ensure that moisture and other volatiles don’t condense on the building’s interior – they can actually be caustic to the building, especially on the steel parts.

To avoid these problems, Terry likes to see, at a minimum, four to six air changes per hour. “We want the entire mass of air in the building to be completely exchanged once every 10 to 15 minutes,” he said.

This is just a guideline for winter that can be changed depending on the size of the facility. In a larger barn, for example, one with 14- to 16-foot sidewalls and open trusses, three air changes/hour may be sufficient. For a barn with low ceilings and high calf density, six air changes/hour would be better.

For what he calls the shoulder seasons – spring and autumn – Terry recommended 20 to 30 air changes/hour, which means exchanging the air every two to three minutes. During summer, in order to provide some cooling in addition to ventilating, he likes to ramp it up to 40 to 60 air changes/hour, which means completely changing the air in the barn every 60 to 90 seconds.

For a naturally vented building, which ideally should be fairly narrow, Terry said – 36- to 40-feet-wide with two rows of calves – the ridge vent should be about two inches for every 10 feet of building width with an eight-inch opening being the minimum.

These buildings are likely to have curtain sidewalls and, according to Terry, a starting protocol on curtain management is if it’s lower than 40º – the curtains closed or maybe cracked an inch. As the temperature rises, the curtain walls should be opened progressively more, so by the time it reaches 68º, they are wide open.

Common Mistakes

One mistake is assuming that fans of equal diameter have nearly equal capacity. Fan diameter is only one of several components, such as the number of blades, the size of blades, the pitch of the blade, the motor speed and the horsepower, that influence a fan’s ventilation capacity.

Another common mistake is lack of maintenance. “Many times I’ve been called to diagnose and remedy a ventilation system, and the only thing needed is a little timely TLC – louvers that don’t easily open, fan grills and blades that are caked with dust and dander, loose belts and frozen idlers,” Terry said. “In and of themselves, these may be minor issues, but when added together, they could be reducing your capacity by 40% to 50%.”

He recommended servicing fans at least once a year, preferably around St. Patrick’s Day when the demand for the fans is the lowest, and if anything needs to be repaired or replaced, it’s not going to have a huge impact on the ventilation in the barn.

He also cautioned against a one-size-fits-all approach in designing or retrofitting a calf rearing facility and recommended taking a road trip to see the designs of other barns and asking questions of the farmers and yourself: How do you want to manage the barn? Are you going to house calves in singles, pairs, triples or small groups? Will you feed via bottles, buckets, barrels or automatic feeders? How will the pens be cleaned and bedded? Will there be a fallow period in the rotation? How will you deal with population surges? Where will the facility be located relative to other facilities? Is expansion a possibility?

“Planning saves a lot of wasted time, money and effort. Remember, you’re going to be in this facility for the next 20 to 25 years, so choose wisely,” Terry said. “It’s always better to over-ventilate than under-ventilate. If calves are properly fed and adequately bedded, they can tolerate a lot of cold. That’s one thing that the hutches have shown us.”