Influence of previous medical treatments on social rank in dairy cows.

Animal health can present economic and animal welfare concerns for dairy farmers. However, it is unknown whether changes in behaviour as a result of sickness have long-term effects, and whether there is a relationship between the social rank of cows in the herd at a moment in time and the medical treatment history of these cows. The behaviour of 100 high-yielding cows in the waiting area (collecting yard) before the milking parlour was studied for five milking sessions to assess the interactions between the cows, as the cows waited to be milked. The cows were filmed, and the interactions between cows were recorded using an ethogram. The summated social rank score of each cow was compared with its medical treatment history. In our analysis, a positive relationship was found between medical treatment history and social rank, however this association was discounted when age was accounted for. When a subsample of cows older than 4.0 years was analysed to examine the relationship between social rank and medical treatment history in older cows, no significant correlation existed. These results suggest that the relationship between social rank and medical treatment history identified in the analysis is predominately an effect of age. This finding is contradictory to the hypothesis that 'a higher historical level of medical treatments, and the disruption and setbacks associated with these disease conditions, would result in a lower position in the social rank.' This preliminary study reports the findings from one particular herd, and across one relatively short time span, and because associations between treatment history and behaviour may be of interest in management decisions for producers, it is recommended that further investigation of this subject is carried out.