Newborn and 5-week-old calves vocalize in response to milk deprivation

Dairy calves are commonly vocal after separation from the cow and during the following weeks while they are fed milk. This study examined the functional and motivational basis for such vocalizations. In one experiment, we found that 14 newborn calves called on average (+/-S.E.M.) 31.4 (+/-7.0) times per day when fed according to conventional management (i.e. twice daily for a total of 51 during 24 h). In contrast, when calves were fed every 4 h and received 81 of milk per day they called only 5.0 (+/-3.4) times over that period. Calls were also higher in fundamental frequency when calves were fed conventionally than when fed more milk, more often (120.6 +/-2.2 versus 109.0 +/-3.1 Hz). In a second experiment, we found that 19 five-week-old calves deprived of milk called on average 9.9 (+/-2.1) times during a 3 h period compared to 0.3 (+/-0.5) times when they had ad libitum access to milk. These results indicate that the vocalizations of milk-fed calves are related to milk feeding practices and that vocal behaviour may be useful in developing methods of separation and weaning that are less distressing for the calf. Analysis of call duration, fundamental frequency and frequency of maximum amplitude indicated that calls of calves in both experiments were individually distinctive, providing a potential basis for recognition of calves by cows. (C) 2001 Published by Elsevier Science B.V.