Calves are often given much less milk than they would want to drink (approximately half) and switched to solid feed abruptly and at an early stage at weaning. Past work has shown that feeding calves restricted amounts of milk slows their development but little research has addressed what calves feel and how hungry they are when under feed restrictions.
This study assessed the effect of milk restriction on calf cognition in two experiments using a modified hole-board test. The researchers expected that the sudden reduction of milk allowance, mimicking what would happen at weaning, would be associated with calves being too hungry to focus on a learning task.
Consistent with the idea that milk fed calves experience hunger when the milk supply declines, the study found that cognitive performance dropped when milk allowance was reduced by half (experiment 1). The research also showed that calves fed restricted quantities of milk are slower to learn new rules (experiment 2).
Although the results do not provide direct evidence that calves felt too hungry to focus, the effect on cognition is consistent with the negative experience of ‘feeling’ hunger. This type of studies can help identify farm animal care practices that when mitigated lead to improved welfare for many dairy calves.
Paper: 'Hunger affects cognitive performance of dairy calves' by Benjamin Lecorps, Raphaela E. Woodroffe, Marina A.G. von Keyserlingk and Daniel M. Weary in Royal Society Biology Letters [open access]