The effects of heat stress on calves has been the topic of a good share of research in recent years. So, too, has been the study of social versus individual calf housing. Now, University of Wisconsin researchers have published a first-of-its kind study that examined the two factors together.
The research project, published in the Journal of Dairy Science, studied the behavior and physiological characteristics of pair-housed preweaned calves as they navigated competing motivations for social contact and thermal comfort.
A total of 50 Holstein heifer calves were housed in 25 pairs in adjoining hutches with a common outdoor run. In each pair of hutches, one was ventilated with 2 open windows at the rear base and the rear bedding door propped open. The other hutch had no ventilation.
Calves were exposed to and evaluated under 4 conditions for 1 daytime hour each – individually or in pairs confined to a ventilated or non-ventilated hutch. The experiment took place from later spring to fall.
The observations were conducted on 2 consecutive days during weeks 4, 6, and 9 of life. Immediately before and after the hutch confinement, respiration rate and rectal temperature were recorded while calves were outside.
On the subsequent third day in the test weeks, the location of each calf was recorded in 15-minute intervals using time-lapse cameras. They were able to move freely among the two hutches and outdoor run without confinement.
Findings included:
- Calves had no hutch preference in week 4 of life, but significantly preferred the ventilated hutch in week 6 and 9 of life.
- The temperature-humidity index (THI) within the ventilated hutches remained constant throughout the study, regardless of the number of calves in them. The unventilated hutches saw a rise in THI when calves were confined inside, which became more pronounced with 2 calves versus 1, and as the calves aged, grew larger, and began ruminating.
- Not only did ventilation mitigate THI increase, but it also produced a significant reduction in respiration rate of calves when they were confined inside. The greatest reduction in respiration rate was observed in paired calves in week 6. Respiration rate inside and outside the hutch remained relatively the same for the non-ventilated hutches for calves of all ages.
- No significant effect on rectal temperature was observed under any of the conditions.
- Regardless of location, calves in the unconfined portion of the study preferred being together about 80% of the time.
The preference for staying together was true even inside the unventilated hutches. The researchers cited previous research indicating that calves have a strong desire to access and maintain physical contact with another calf.
They speculated that, when considering social contact versus physical comfort, calves were willing to endure higher temperatures and potentially poorer air quality to be with their partner.Even though evidence in the study indicated the ventilated hutches were more comfortable, calves were willing to forego that comfort to stay with another calf.
Your Next Read: The Hidden Cost of Heat Stress on the Unborn Calf
