Abstract:
The objective of this experiment was to determine the differences in behavioural changes observed in 6-month-old beef calves at weaning in relation to milk yield availability from their dams. Eighteen Hereford or Hereford × Angus crossbred primiparous cows from a single herd remained with their calves suckling until the beginning of the experiment (194.1 ± 1.9 days after calving). On day 0, calves were moved to a 100-m2 corral far from their mothers, which were taken to a field more than 1000 m away, and returned to the original paddock on day 1. Milk production was determined monthly during the lactation period in 14 of the 18 cows. Calves' behaviour was recorded using instantaneous sampling of individual animals in each group every 10 min from 0800 to 0950, 1200 to 1350, and 1600 to 1750 hours. Recordings were performed from day –3 to day 5, except on day 0. The calves from the five cows with higher milk yield (HMY) and the calves from the five cows with lower milk yield (LMY) were considered for data analysis. Milk yield was greater in HMY than LMY cows throughout all the lactation. HMY calves tended to suckle more frequently than LMY calves. There were no differences in average daily gain after weaning between HMY and LMY calves. However, HMY calves were heavier at weaning than LMY calves. The frequency of grazing, ruminating, walking and standing differed between HMY and LMY calves, and was affected by weaning. For example, calves from HMY cows spent less time grazing before and after weaning than calves from LMY cows. There were also interactions between group and time on the frequency of these behaviours. Overall, we conclude that the behaviour of 6-month-old beef calves at weaning differed according to their mothers' milk yield, and their developmental growth stage.