Relationships between time budgets, cortisol metabolite concentrations and dominance values of cows milked in a robotic system and a herringbone parlour

Abstract

In the present study we investigated the relationships between time budgets, concentrations of cortisol metabolites in the faeces, and dominance values in two groups of 30 dairy cows. One group was milked in a single-box robotic milking system with partially forced cow traffic (R-group). The other group was milked twice daily in a 2x6 herringbone-parlour (HP-group). Both groups consisted of Brown Swiss and Austrian Simmental cows and were housed in identical conditions. Direct observations of social behaviour and 24-hour video recordings were conducted during six two-day blocks. The dominance value (DV) of each cow was calculated from the antagonistic interactions observed directly. The time budget (lying, feeding, other activity) of each cow was calculated from scan samples of the video tapes. On the day after each observation block, faeces of all individual cows were collected to determine the concentration of cortisol metabolites as an indicator of baseline adrenocortical activity and possible chronic stress (CC). The groups did not differ significantly (MWU tests, alpha=0.05) in lying or other activity. Cows in the R-group spent significantly less time feeding than cows in the HP-group (9.9%±0.4% vs 10.6%±0.3%). The Pearson correlation matrix for the time budget parameters and DV within groups indicated negligible relationships among the parameters. In a between-group comparison for the subset of lactating cows only, the groups did not differ significantly in feeding behaviour. The results were otherwise similar to those for the full data set. There were no group differences with regard to CC. Within the R-group, CC of lactating cows was significantly correlated with lying (rp=-0.56, p=0.007) and other activity (rp=0.57, p=0.005). Relationships between DV, time budget and CC were otherwise negligible. Social rank did not influence the relationship between CC and time budget in either group.