Behavioural predictors of the start of normal and dystocic calving in dairy cows and heifers

The individual monitoring of dairy cows around the time of calving is important to identify calving difficulties or health problems as early as possible. This study aims to identify whether there are differences in the behaviour before calving, between heifers and cows, and between those that are assisted at calving and those that are not. Behavioural recordings of Holstein–Friesian cows and heifers were made before and during calving. Video recordings from 12 cows and 12 heifers were selected so that half of each group were observed to have calved without assistance and the other half were identified as having been assisted at calving. To compare the 12 h prior to the calf being expelled with a 12-h control period during late pregnancy, continuous focal observations were made from the video recordings to quantify frequencies and durations of behaviours during 2-h periods. An increased duration of tail raising was observed before calving and this was seen earlier in heifers, from 4 h before calving, compared with only 2 h before calving in cows. Lying frequency increased as calving approached from 6 h before calving in unassisted animals, but only during the final 2 h before calving in assisted animals. These results show important differences between heifers and cows in their pre-calving behaviour which must be taken into account when predicting the time of calving from behaviour. However, for those animals that subsequently required assistance, no behavioural early-warning signs of a difficult calving were identified.