The effects of part-time dam-contact and stepwise weaning and separation on the voluntary human approach behaviour of dairy calves

Abstract

Dairy calves are commonly reared without contact with their dam, which facilitates a human-animal relationship based on close human contact and feeding. Dam-contact may negatively affect calves’ relationship with humans. The current study investigates the effect of dam-contact and weaning method on calves’ response to humans. A total of 69 dairy calves were allocated to one of three dam-contact treatments [Control (separated from dam after 24 h), Whole-day (housed with dam for 23 h/d), and Half-day (housed with dam for 10 h/d)]. Within each treatment, calves were allocated to one of two weaning treatments [Stepwise (weaning off milk at eight weeks, dam-separation/pen change at nine weeks) or Simultaneous (weaning off milk and dam-separation/pen change simultaneously at nine weeks), i.e Control were weaned in the same manner but only the pen change was possible at the separation step, as calves were already separated from the dam]. All animals received a similar amount of human contact, except control calves who were additionally fed milk by teat bucket twice a day. Calves were tested in a random order within block using a human approach test followed by an animal approach test conducted in a 2.5 m x 10 m arena at 10 weeks of age. Stepwise-Control calves had shorter latencies to first approach the test person than Stepwise-Whole-day (p < 0.05, median survival time of Stepwise-Control: 11 s, Stepwise-Whole-day: 111 s and Stepwise-Half-day: 52 s). Among Simultaneous calves, no dam-contact treatment differences were detected for the latency to first approach. Similarly, Stepwise-Control calves had an odds ratio (95% CI) of 24.2 (1.6–365.9, p < 0.05) for coming within 1 m of the test person vs Stepwise-Whole-day calves and 12.5 (1.1–141.1, p < 0.05) vs Stepwise-Half-day calves. Throughout the test period Simultaneous-Control vocalised less [estimated mean no. of vocalisations (95% CI), 3.6 (2.1–6.4)] than both Simultaneous-Whole-day [18.2 (12.8–25.9), p < 0.01] and Simultaneous-Half-day [15.7 (11.0–22.5), p < 0.01] while there was no difference under Stepwise. As expected, Control approached faster and were more likely to come close to the test person than dam-reared calves, but exclusively after the stepwise weaning and separation. For calves tested one week after simultaneous weaning and separation no effect of the dam-contact treatments was found, except a higher frequency of vocalisations for dam-reared calves. This implies that controlling for the stress level related to weaning and separation from the dam is important when interpreting human-animal relationship tests, as dam-contact treatment effects appeared to be affected by high levels of weaning stress.