The detrimental effects of social isolation

Research has shown that many species develop abnormal behaviour when socially isolated. In nature, dairy calves tend to form strong social connections at a very young age.^[4] Understanding the effects of social isolation on a variety of behavioural criteria, therefore, required choosing the correct housing for calves. It turns out that socially reared calves are less fearful than calves reared in social isolation.^[5] Social buffering, or the ability of social partners to decrease the effect of stressors during a challenge, has strong effects on calves. Calves vocalize less when in a new area when they are accompanied by calves they are familiar with, as compared to when they are with unfamiliar calves.^[6] Individually housed calves have a stronger vocal response to weaning than paired calves.^[7]

As farm animals often experience novel events such as changes in pen location, regrouping, and changes in diet, the ability to cope with novelty is quite important. However, it has been shown that individually housed calves are far more reactive to social and environmental novelty.^[8] On the contrary, socially housed calves have a reduced behavioural and physiological reactivity to a variety of stimuli, including being less fearful of new food items. Additionally, early-life social isolation leads to lower performance on key measures of cognition and learning.^[9]

Thus, calves raised in isolation seem to exhibit deficient social skills, difficulty coping with new situations and poor learning abilities, all of which could hinder their performance on dairy farms which always have changing environments. These negative effects of social isolation might persist. While the evidence does seem to suggest that group housing of young calves is beneficial, it's important to fully understand both the potential positive outcomes and the constraints associated with it.

There is a large and growing body of evidence that shows that social housing positively influences dairy calf performance. Socially housed neonatal dairy calves have higher intakes of solid feed and increased body weight gains compared to individually housed calves. The exact mechanism of social influence on feeding behaviour needs further study. Many studies have demonstrated a positive influence of social housing on various calf performance indicators such as early onset of puberty and increased milk production in first and later lactations.^[10]

The challenges associated with the social housing of neonatal calves can, for the most part, be overcome with proper management. There have been reports of increased cross-sucking^[13] when calves are housed socially, but other studies have reported little or no increase in this behaviour^[12]. The use of teat feeders, enhanced milk feeding programs, and more gradual weaning procedures seem to mitigate the desire to cross-suck.

Increased competition and aggression have been reported in calves that are socially housed. This behaviour can be managed by providing enough milk and ample feeding stations, and by designing and placing these stations effectively.

Arguably, one of the main reasons dairy farmers isolate neonatal calves is to reduce the risk of disease, in particular respiratory disease. There is however little evidence of a consistent relationship between calf health and individual housing. Many empirical studies have found no health advantage of housing calves individually^[13]. Factors such as the amount and quality of milk fed, hygiene, group size, ventilation, colostrum protocols and bedding management have much more influence on the risk of disease than group housing.