The effects of regrouping and stocking density on social behaviour, lying behaviour and locomotor activity of mid and late lactation dairy cows

In free-stall systems cows are frequently moved among pens and regrouped. This practice involves individuals being mixed with unfamiliar cows, and stocking density often varies from before to after regrouping. Two separate lines of evidence suggest that regrouping and changing densities have negative impacts on cows welfare; but no study to date has assessed the combined effects. The aim of this study was to test the effect of changes in stocking density at the time of regrouping on the competition, feeding and lying behaviours and locomotor activity of dairy cows. By manipulating group size (6 vs. 12 cows) and pen size (12 vs. 24 stalls) three different stocking densities were created (25 %, 50 % and 100 %). Four groups of Holstein cows were regrouped weekly for 4 weeks and the stocking density changed from before to after each regrouping. The change in density varied from a decrease by a factor of 4 (100% to 25%), a decrease by a factor of 2 (100% to 50% or 50% to 25%), no change (50% to 50%), an increase by a factor of 2 (25% to 50% or 50% to 100%) and an increase by a factor of 4 (25% to 100%). Displacement at the feeding area, feeding time, lying time and the number of steps were scored. The daily means for each group were used to calculate the difference in responses from one day before to one day after each regrouping. Competition at the feed bunk changed after regrouping. The nature of the change was dependent upon the change in stocking density; when density decreased the number of displacements decreased. Changes in lying behavior and locomotor activity after regrouping also varied with changes in stocking density; when stocking density decreased lying time increased and number of steps increased. In conclusion, results of this experiment show that the change in competition behaviour from one day before to one day after regrouping varies with the change in stocking density at regrouping; and this change in competition results in changes in lying time and locomotor activity of cows.Land and Food Systems, Faculty ofGraduat