Cross-sucking and gradual weaning of dairy calves

To examine the effect of gradually weaning calves off milk on cross-sucking, and the relationship between cross-sucking and energy intake, 32 Holstein calves were housed in groups of four and allowed 12 L/d of milk until the process of weaning began. The process of weaning was either abrupt at 41 d of age or gradual, taking place over 22 d, 10 d or 4 d so that weaning was completed at 41 d of age. Digestible energy intake (DE) was calculated from milk and starter intakes. The calves were observed for 6 d before weaning was complete and for 3 d after weaning was complete, and the duration of all instances of cross-sucking during 8 h/d was recorded. The frequency of vocalizations during 2 h/d after weaning was also recorded. There were no differences between male and female calves in the duration of cross-sucking. Before weaning began and the calves were drinking their full allowance of milk, very little cross-sucking occurred. However, when calves began to be weaned, cross-sucking increased, and cross-sucking during the period before weaning was completed was highest for calves gradually weaned over 22 d compared to the other three treatments (median duration = 12 min/d vs <3 min/d). The duration of cross-sucking was negatively correlated with DE intake (r = −0.62, P < 0.001). After weaning was complete, the duration of cross-sucking increased but this was not affected by weaning duration, and was unrelated to DE intake, which was low for all calves. The duration of cross-sucking was negatively correlated with the frequency of vocalization (r = −0.45, P < 0.01). Cross-sucking is a response of calves to a reduced energy intake due to weaning off milk. However, weaning at the ages typical of dairy production may be too early to allow the calves to obtain sufficient energy from solid food, which may explain the sharp rise in cross-sucking when calves are fully weaned. Cross-sucking and vocalizing appear to be alternative responses of calves to a reduced DE intake occurring once calves are weaned off milk.