The effects of age and experience on behavioural development in dairy calves

• Published in: Applied animal behaviour science 2006-08, Vol.99 (1), p.41-52
• Main Authors: Lauber, Mariko Ching Yin, Hemsworth, Paul Hamilton, Barnett, John Lawrence
• Format: Article
• Language: English
• Subjects: Age; animal age; animal behavior; animal characteristics; Behaviour; calves; Dairy calves; Development; Experience; fearfulness; heart rate; learning; temperament
• ISSN: 0168-1591; 1872-9045
• DOI: 10.1016/j.applanim.2005.10.009

The effects of age and experience on behavioural development were examined in 28 male dairy calves. Fourteen calves (Group 1) were tested at 6 weeks of age and another 14 (Group 2) tested at 2 and 6 weeks of age, on an Open Field, a Novel Object and a Startle test, as well as a discrimination learning task requiring the animal to locate the single teat in a three-teat feeder that delivered milk. Eleven behavioural variables were measured across the four tests, as well as heart rate pre- and post-exposure to the behavioural tests. Using Bonferroni t-test ( α = 0.0045), the only statistically significant difference in behaviour due to age was in latency to interact with novel object in the Novel Object test. Notwithstanding the very conservative Bonferroni-adjusted error rate, there was a trend for calves at 2 weeks of age to withdraw less from the startle object in the Startle test than at 6 weeks of age ( P = 0.008), to interact less with the novel object in the Novel Object test ( P = 0.046) and to require more trials to reach the learning criterion ( P = 0.031). Interestingly, heart rate showed a significant increase with age in all three behavioural tests ( P < 0.005) and with age combined with experience ( P < 0.005). There was also a relatively large decrease in the number of defecations (38%, P = 0.030) in the Open Field test, and latency to interact with objects in the Novel Object test showed a substantial but not significant increase (41%, P = 0.044), possibly because of relatively large variances. Learning rate within Group 2 decreased substantially, but not significantly, between 2 and 6 weeks of age (21%, P = 0.009). Within the context of the very conservative error rate used, together with the small sample size and relatively large individual differences in the present study, the results provide some limited evidence that calves become more behaviourally, and possibly more physiologically, responsive to potentially stressful situations as they age from 2 to 6 weeks and that the changes may be moderated by experience.