The detrimental effects of social isolation

The question of how to house neonatal dairy calves has, in recent years, become the subject of much debate. A significant majority of dairy farms currently follow a protocol in which newborns are housed individually and away from social contact until they are weaned. While this protocol is most often intended to guard the health of young calves and keep them free from diseases and behaviours which may threaten their health and future production, concerns have come to light about the potential negative effects this social isolation has on calves' behaviour, performance and health.

In nature, while calves are fully dependent on, and stay very close to, their dams during the first week of life, by the second week they begin interacting with peers as well as forming small groups. They start grazing and ruminating by about the third week and graze regularly with the herd from about three months to six months of age. This social learning influences behavioural development, including knowledge of suitable food items1 and lack of fear of new or unfamiliar foods.2 So, what happens when calves are reared in individual pens without this social interaction? And, is it possible to house neonatal calves socially and yet steer clear of potential health and behavioural pitfalls that push many farmers to house neonatal calves individually? In "Effects of group housing of dairy calves on behavior, cognition, performance, and health," J.H.C. Costa et al.3 explore these questions by reviewing the available scientific research on the effects of social isolation on calves' development and comparing it to the effects of various types of group housing. What they found bolsters the arguments of those who promote social housing for pre-weaned dairy calves.

Effects of social isolation

Research has shown that many species have abnormal behaviour and developmental problems when socially isolated. Dairy calves are no exception. As in nature calves tend to form strong social connections from a very young age,4 understanding the effects of social isolation on a variety of behavioural criteria is a good place to start in evaluating calf housing choices.
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 in cattle. Examples include the fact that 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 And, individually housed calves have a stronger vocal response to weaning (indicating stress) than paired calves.7

As farm animals often experience new or 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, reduced behavioural and physiological reactivity to a variety of stimuli, including being less fearful of new food items, is seen in calves that have had early social contact. Additionally, early life social isolation also leads to lower performance on key measures of cognition and learning than in those raised socially.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. While there aren't too many longitudinal studies on this issue, based on their findings, Costa et al. do posit that the negative effects of social isolation would 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 that come along with such arrangements.

The positive outcomes of group housing

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 improved body weight gains compared to individually housed calves. While the exact mechanism of social influence on feeding behaviour needs further study, Costa et al. found that study after study for the last 15 years has documented a positive influence of social housing on all manner of calf performance. These early gains can also contribute to earlier onset of puberty and increased milk production in the first and later lactations.10

The challenges of group housing

While social housing of neonatal calves does pose some challenges, it's important to note that they can, for the most part, be overcome with proper management. Indeed, while there have been reports of increased cross-sucking11 when calves are housed socially, other studies have reported little or no increase in this behaviour12. Therefore, it's clear the situation can be managed. Costa el al. note that the use of teat feeders, enhanced milk feeding programs, and more gradual weaning procedures seem to mitigate the desire to cross-suck. Additionally, while increased competition and aggression have been reported in calves that are socially housed, this behaviour, too, can be managed. By providing enough milk and ample feeding stations, and by designing and placing these stations effectively, there is less competition.

Arguably, one of the main reasons many dairy farms isolate neonatal calves is concern for calf health and spread of disease, especially respiratory illnesses. However, Costa et al. found little evidence of a consistent relationship between calf health and individual housing. In fact, they cite many empirical studies which have found no health advantage to individually housing calves, compared with housing in small groups13. As with other the other challenges mentioned above, management is key. Through their comprehensive research review, Costa et al. conclude that the amount of milk fed (more and of a higher quality is better), hygiene, group size, ventilation, colostrum protocols and bedding management have much more to do with influencing risk of disease than does group housing.

Ultimately, the positive aspects of housing young calves socially do seem to outweigh the negative outcomes derived from their social isolation. With proper management, the perception of risk that comes with group housing can be minimised and pre-weaned calves can be given a better chance at meeting higher performance goals.