Calves are social animals, yet many spend their first weeks of life housed individually. Early social contact can influence how calves learn, behave and respond to stress, giving producers reasons to consider pair housing beyond simply changing their housing systems.
In some regions, social housing is also becoming a requirement. Canada’s Dairy Code of Practice calls for healthy, thriving and compatible calves housed indoors to be kept in pairs or groups by four weeks of age beginning April 1, 2031. The code also requires physical contact with another calf for outdoor-housed calves, subject to exceptions. In the European Union, calves generally cannot be kept in individual pens beyond eight weeks, unless a veterinarian certifies that isolation is necessary for health or behavioral reasons.
Dr. Jennifer Van Os, an animal welfare specialist at the University of Wisconsin-Madison, studies how social housing affects preweaned calves. Her research points to potential benefits for behavioral development and stress resilience, along with questions about how housing design influences calf health and performance.
Social Housing Benefits Beyond Winter
Pair housing gives calves opportunities to play, interact and learn from one another. Socially housed calves can be more willing to explore unfamiliar environments and try new feeds. These experiences may help them adapt to changes in their surroundings and management.
Weaning is one example. Calves must adjust to changes in nutrition and routine, and early social experience may help them handle that transition.
“When calves are raised in pairs or groups from a young age, they show better stress resilience, particularly in the context of weaning. We know that weaning is always a stressful time in a calf’s life, but when calves are raised in pairs or groups, that stress response is dampened,” Van Os says.
Research has also found that socially housed calves generally eat similar amounts of starter and grow as well as, or sometimes better than, individually housed calves. Results vary with management and study design, but the evidence suggests social housing can support behavioral development without necessarily compromising growth.
Pair Housing and Cold Stress in Calves
Social contact may offer another potential benefit during winter: calves can share body heat. Van Os and her research team explored this possibility in a study of 48 Holstein heifer calves housed in outdoor hutches during winter. Sixteen calves were housed individually, while 32 were housed in 16 pairs.
When calves were confined to their hutches for one hour, the air temperature inside pair-housed hutches increased by about 2.3°C, compared with 1.4°C in individual hutches. Researchers found no differences in rectal temperature, body weight, average daily gain or feed conversion.
“We hypothesized that when calves are pair housed, they might be more resistant to cold stress in the winter because they can huddle for warmth. We found some evidence to support this, that perhaps your housing could be a way to protect calves against cold stress in winter extremes,” Van Os says.
Practical Tips for Pair-Housing Calves
The benefits of social housing depend in part on how the system is designed. Simply placing two calves in a hutch intended for one can leave them short of space, especially when they prefer to rest together indoors rather than use an outdoor run.
“The problem is the calves really like to spend their time together. So if they’re not lying outside in the fenced area, they’re going to be together inside the hutch and then their space allowance is restricted,” Van Os explains.
Connected hutches and outdoor runs can be a starting point, but you need to ensure calves have enough room to rest, move around and access feed and water. Van Os favors simple rectangular pens or other layouts that give calves adequate space to interact without crowding.
When forming pairs, consider three factors:
- Pair calves early. In Van Os’ survey, more than two-thirds of veterinarians preferred pairing calves by two weeks of age.
- Match age and size. Ideally, calves should be less than a week apart in age, with no more than a two-week gap. Similar body size can help limit competition at the feeder.
- Monitor calves individually. Ensure both calves can access milk and starter, and watch intake, growth and health to identify animals falling behind.
Feeding management deserves particular attention. Adequate milk intake and nipple-based feeding that allows calves time to suckle may help reduce competition and cross-sucking. You should also have a plan for identifying calves that are not keeping up with their pen mates.
Ventilation needs to work across seasons, too. Shared body heat may help warm a hutch in winter, but heat can build up in warmer weather. Research from Van Os’ lab showed that passive ventilation modifications helped reduce hutch temperatures and calf respiration rates.
Calf Health Fundamentals Still Come First
“Calf health is multifactorial,” Van Os says. “A lot of the same principles apply whether housing calves individually or in groups. I think it’s important for a farmer to have all their ducks in a row around calf health regardless of their group size.”
Social housing does not replace the basics of good calf management. Effective colostrum delivery, adequate nutrition, clean and dry bedding, appropriate ventilation, sanitation and regular health checks remain essential.
Cross-sucking is one concern producers may have when considering pair housing. Although it has raised questions about possible effects on udder health later in life, current evidence has not established a direct link between early pair housing and subsequent mastitis or blind quarters.
These concerns should be addressed alongside the overall feeding and housing system, rather than assuming group size alone determines calf health.
Planning a Successful Transition to Pair Housing
For farms considering pair housing, Van Os recommends evaluating facilities, feeding systems, labor needs and health protocols before making a large-scale change. Starting with a few pairs can help producers and veterinarians assess calf health, growth, feeding behavior and workload before expanding.
“The farm not only needs to be ready, but they also want to do this. There are so many logistical issues to think through in this transition. It has to be something that a farm is interested in doing,” Van Os says.
Pair housing gives calves opportunities for social development and may help them adapt to stressful events. It may also offer a benefit during cold weather, although more research is needed to establish that advantage. The goal is to build a system that allows calves to benefit from social contact while maintaining the nutrition, space, ventilation and health management they need to thrive.
