The findings, published in the Nature journal Scientific Reports and led by the University of Bristol, shed fascinating new light on how hungry animals sacrifice play and put finding food first. But calves which were given more food were more inclined to play.
Researchers compared the behaviour of two groups of calves fed different amounts daily – one on 12 litres of milk and the other on 6 litres, the normal milk quantity given in dairy farms – when asked to find milk in a maze.
The results showed calves fed less had better recall and were quicker to complete tasks with a milk reward. By contrast, calves fed more were less engaged in the milk reward tasks and played more.
Lead author Jillian Hendricks, a PhD student at the University of Bristol Veterinary School, said: "The study is among the first to show that hungry animals will trade-off play to prioritise finding food. It expands our understanding of how hunger suppresses other competing motivations and emotions, like play opportunities.
"It also paves the way for future research, exploring how animals prioritise conflicting behaviours and incentives. This is especially important in farm animals who are often offered limited opportunity to express certain behaviours."
Study co-author Dr Ben Lecorps, Senior Lecturer and Animal Welfare Scientist at the University of Bristol Veterinary School, added: "The key takeaway for dairy farmers is that the standard milk allowance for calves may disrupt other important behaviours, which indicate that they may experience hunger.
"The research suggests feeding calves more may not only be beneficial as it suppresses hunger, but also because it contributes to the expression of other important behaviours like play."
Although the two groups of 10 calves were given a different milk allowance over a three week period, they all went without food for 16 hours before being tested, as part of normal farm feeding practices providing two meals a day once at 8am and once at 4pm.
Dr Lecorps added: "Despite this long period without milk, calves fed more still prioritised playing. This tells us a lot about how much play matters for them."
Paper
'Calves fed more milk prioritise play over feeding in a hole-board test' by J. Hendricks et al. in Scientific Reports
