The development of behaviour patterns and an assessment of temperament of dairy heifers
Dennison, Sheila Ganson Copley
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The main aims of this study were 1) to describe the development of behavioural patterns in dairy heifers, 2) to investigate individual differences in behaviour and temperament, 3) to assess the temperament of each during milking and 4) to determine whether measures of early behaviour are related to temperament at a later age or to production measurements.Time based focal animal samples of twenty Friesian heifer calves over a period of two years recorded the activity of the calf and its nearest neighbour. A study of beef suckler calves reared with their dams was available for comparison of early development. The animals reactivity to being touched was tested approximately weekly and its temperament during milking was assessed. Data on liveweight measurements and daily milk yields were available.Development of the heifer's behavioural activities is shown graphically, either as proportion of time spent or frequency of occurrence. The development is considered in two ways 1)development in relation to chronological age, and ?_)development in relation to period of time within a particular rearing condition. However, the development was similar in both cases. Testing of the mean values of the activities for each separate rearing condition, normally experienced by dairy calves during their rearing, showed significant changes. Diagrams of significant sequential changes of activities show the development of the context of these behavioural actions. These results are compared with those obtained for field calves to indicate where environmental conditions may be affecting the development of the dairy calves behaviour patterns.The animals were then considered individually. Individual differences in the proportion of time spent in different activities was not consistent in each rearing period. The heifers social profile is represented by histograms of the frequency of expression of two categories of social behaviour, social licking and aggression. Associations between heifers, measured as the most time spent as its nearest neighbour, was only observed between a pair of twins. The reactivity of the heifers to being touched showed that most of the heifers were consistent in their reaction from an early age. Investigation of position within the herd and ease of entry to the parlour during the milking routine showed that heifers were recorded more often in the in the last third of milking group which was also associated with being pushed into the parlour by the dairyman. investigation of correlation between the behavioural measurements and between the behavioural and production measurements (i.e. growth rate of the heifers and the mean daily milk yield) is discussed. For the behavioural measurements, only the correlation between the frequency of initiating aggression and milking temperament was significant at p <0.05 level. However, three other correlations approached significance i.e. correlation of proportion of time spent passively as a calf with frequency of initiating aggression, frequency of initiating social licking with proportion of times pushed into parlour and proportion of times pushed into parlour with milking temperament. This led to the hypothesis of a trend in the development of behaviour characteristics of dairy heifers.There appeared to be little relationship between the behavioural measures of the heifers and measures of their productivity with only the correlation between frequency of initiating social licking and mean daily milk yield reaching the p <0.05 level of significance.Finally, a discussion of these findings in relation to theories of development(e.g. effect of environment, early experiences) and their implications for animal husbandry is presented.