Keeping dairy calves in hutches cool and comfortable
The warm season has arrived in Wisconsin, and dairy producers will have turned on the fans or soakers for their lactating cows. At first glance, young calves may seem like less of a concern when it comes to heat stress. They produce less body heat from rumination and have greater relative surface area for heat loss. Still, in the summer, they may experience dehydration, poor welfare, and show reduced appetite, feed intake, and growth.
Researchers in Ohio found better weight gains and feed efficiency for calves housed in single pens with wire-mesh panels when fans were turned on during the day. Likewise, researchers in Florida found that calves group-housed in pens with automatic milk feeders had greater grain intakes when fans were turned on at 68°F.
Calves housed in outdoor hutches are more exposed to environmental extremes compared to those housed in barns. Depending on the style, plastic hutches can sometimes create a greenhouse effect, gaining heat from the sun and warming up inside. To prevent this, shade is the best defense. Trees or shade cloth blocking at least 80% of UV light have been shown to reduce the temperature inside the hutch.
Hutches can be ventilated to increase airflow and heat exchange. Researchers in Washington found that on days when hutches were raised with cinder blocks, calves had lower respiration rates. Although elevating the hutch is a simple solution, some producers have expressed concerns about calf safety. An alternative is to prop open the rear bedding door, install adjustable windows, or use a combination of these methods. When UW-Madison Dairy Science graduate student Kim Reuscher was an undergraduate at Tarleton State University, she compared these methods on large heifer-grower operations in Texas.
More recently, Kim tested 32 pairs of heifer calves at UW-Madison’s Blaine Dairy in Arlington, WI last summer. Each pair was housed in adjacent individual Calf-Tel hutches with a shared fence. Once the calves were paired at around 1 week old, we added ventilation to one of the hutches in each pair by propping open the back bedding door and opening the 2 rear ventilation windows near the base of the hutch.
We looked at hutch use in 20 pairs of calves when they were 8 weeks old, right after they were weaned. During the warmest times of day between 12 and 5 pm, we monitored their behavior using time-lapse footage every 5 seconds. Overall, calves spent 68% of their time in the ventilated hutch, with 16 out of the 20 pairs spending over half of their time in that hutch.
On other days during the study, we kept calves inside the hutches for 1 hour a time using a wire fencing panel. They were kept either in separate hutches or in the same hutch together, and we repeated this for both the ventilated and non-ventilated hutch in each pair. Before and after calves were placed inside the hutches, we measured signs of heat stress, including respiration rate.
When calves were in the non-ventilated hutch with airflow only through the front door and roof vents, their respiration rates stayed relatively stable over the course of the hour. This indicated that these hutches did not have a greenhouse effect. Calves did not accumulate heat and get hotter over time relative to when they were outdoors – but they did not get cooler either.
In contrast, when calves were in the ventilated hutch, their respiration rates were reduced by 10 to 20 breaths/min over the course of the hour. This demonstrated that hutch ventilation had a cooling effect, helping the calves dissipate heat. These patterns were consistent whether there was only 1 calf in the hutch a time, or both calves in the pair, and whether the calves were in week 4, 6, or 9 of life.
Kim is now analyzing the calves’ behavior over 24-hour periods to see how their use of the hutches changes depending on time of day and weather. She is also evaluating footage from weeks 4 and 6 of life see if their preferences change as they develop and produce more body heat. Finally, she is also examining rectal, skin, and eye temperatures to see how these indicators of heat stress change, depending on hutch ventilation and the number of calves inside the hutch. We will share this information once available.
In the meantime, our initial results are a promising indication that hutch ventilation translates quickly into reduced respiration rates for calves in hutches, even when they are pair housed. Furthermore, the calves seek out hutches with ventilation. By voting with their feet, the calves indicated a significant preference for the cooler environment.
Van Os is an Assistant Professor and Extension Specialist in Animal Welfare, Department of Dairy Science, University of Wisconsin-Madison