Pair housing benefits performance and activity of dairy calves with influences of season.

Although the most common practice to house dairy calves individually for at least the first weeks of life, animal welfare concerns increasingly promote pre-weaning social housing systems. Housing dairy calves with social contact enables natural behaviours (e.g., social grooming and play), reduces fear and avoidance of novel environments, and is likely to provide affective benefits. In practice though, housing calves with social contact before weaning remains largely voluntary, although recent data suggest that dairy farmers generally view social housing as beneficial for calf behaviour, but the effects of social housing are viewed more ambiguously with respect to health and performance.

While there are various approaches to implement social housing in calves, pair housing may represent the simplest approach, enabling the benefits of social contact while maintaining similar feeding practices to individual housing and often requires minimal facility changes. In addition, whereas group housing has been linked to health risks (e.g., increased risk of respiratory disease; gastrointestinal disease and mortality), pair housing does not appear to adversely affect health. Pair housing also has been shown to benefit calf performance, stimulating acceptance of novel feeds and meal frequency, and supporting greater total feed intake and growth, particularly during weaning. However, the performance effects of housing dairy calves in pairs may depend on environmental conditions, as social contact may modulate the effects of non-optimal climatic conditions. When ambient temperatures are low, calves appear to seek more frequent physical contact, which can reduce heat loss. Accordingly, housing calves in pairs may increase hutch temperatures during winters. When ambient temperatures are high, social contact may increase overall heat load and exacerbate the detrimental effects of heat stress, particularly as housed calves may prioritize social proximity over thermal comfort. It is also possible that suppression of feeding coinciding with heat stress and reallocation of time to mitigate heat stress may reduce stimulating effects of social contact to a point where social housing is less likely to evoke intake and growth improvements.

These were the questions raised by the authors cited and therefore the objective of their study was to evaluate the effects of pair housing from birth compared with individual housing on dairy calf performance and activity within different seasonal conditions.

In the study, Holstein heifer calves within 24 h of birth were assigned to either individual (IH; n = 50 pens) or pair housing (PH; n = 50 pens), balanced across seasons in a humid subtropical climate (cool season, 17 ± 5°C and warm season, 26 ± 3°C, temperature-humidity index consistently >65). The calves received 8 L per day milk replacer, until gradual weaning over 10 days beginning at 43 ± 3 days of age, and calf starter and water ad libitum. The presence of fever (≥39.4°C) and scours (faecal consistency assessed visually at the pen level) were assessed 5 days per week. The calves were weighed at birth, before and after weaning, and one week post-weaning. Starter intake was recorded 4 days per week. Standing time was determined using leg-based accelerometers.

The results showed that calves born in the cool season scoured later and for fewer days, with no effect of housing method. Fever occurrence was similarly reduced in the cool season, in interaction with housing treatment; fewer PH than IH calves had a fever in the cool season. Calves in PH pens consumed more starter by week 5 of life, had greater ADG pre- and post-weaning, and had greater body weight by the end of weaning, compared to IH calves. Some performance advantages attributed to PH were most apparent in the cool season, including starter intake during weaning and post-weaning ADG. Calves in PH pens maintained greater body weight one post-weaning, with no effect of season. The calves in the PH pens spent more time standing, particularly in the evening, with daily peaks in activity falling later in the day during the warm season.

In conclusion: The results showed benefits to pair housing compared with individual housing, in addition to novel insight into the modulating effects of seasonal conditions on performance. The findings illustrate advantages for pair-housed calves, characterized by increased feed intake, growth, and activity. Evidence of interactive effects between housing and season of birth could be interpreted to suggest either that the relative advantages of social housing may be greater in cool weather or lessened by exposure to heat stress.