Influence of artificial vs. mother-bonded rearing on sucking behaviour, health and weight gain in calves

In artificial rearing, calves are often fed via an automatic milk feeder and have no opportunity to perform natural sucking behaviour. The majority of these calves show abnormal oral behaviours (e.g. cross-sucking). Furthermore, diseases are also a main problem in artificial rearing of calves, and weight gain prior and after weaning is often suboptimal. The aim of this study was to investigate sucking behaviour, health and weight gain in calves that were reared artificially or with unrestricted or restricted contact to their mother, respectively. Two groups of calves suckled by their mothers (unrestricted contact, n = 14; twice daily for 15 min before milking, n = 15) were compared to two control groups that were both fed via an automaticmilk feeder (six times daily, n = 14; twice daily, n = 14). The calves of the four treatment groups were kept in the same barn and cows were milked twice daily. To analyse sucking behaviour, the calves were observed three times (at ages of 4, 10 and 15 weeks). All calves were weaned at 13 weeks of age. The health state of each animal was assessed daily and veterinary treatments were counted until weaning. The animals were weighed weekly until 3 weeks after weaning. For statistical analyses, linear mixed-effects models were used. Only one mother-fed calf (twice suckled) performed cross-sucking, while 13 of 14 calves in both automatic fed treatments performed crosssucking (p< .001). The health state of both mother-fed groups was poorer (p = 0.046, caused mostly by diarrhoea), but the number of animals that had to be treated by a veterinarian did not differ. During the milk feeding period, weight gain was better in mother-fed calves (p< .001). After weaning, the weight gain of all four treatment groups was diminished. This effect was stronger in mother-fed calves than in automatic fed calves (p< .001). The higher weight gain in mother-fed calves before weaning can be explained by the large milk amounts the calves received. Mother-bonded rearing prevented the development of cross-sucking, even when calves only met their mothers twice daily for 15 min each. Thus, we assume that calves can deal with housing conditions common in artificial rearing when contact with the mother is possible, even if this contact is very limited. We conclude that artificial milk feeders are not able to satisfy sucking motivation completely. Altogether, we reason that permanent and restricted contact with the mother has great behavioural advantages.