Abstract: The effect of separating, dominant and subordinate cows on production, behaviour and the relationships between dominance and production parameters, was studied using 80 grazing cows, offered-forage supplements in experiment 1. Dominance was principally related to body weight, but in the pooled data it was also positively correlated with lactation number and negatively correlated with grazing time. In experiment 2, seventy two spring calving cows were classified as dominant or subordinate on the basis of aggressive interactions and further divided by two factors: dominant and subordinate cows grazed together or apart, and with or without a hay supplement. Dominant cows produced more milk. Both dominant and subordinate cows gained more weight and lay down for longer, when kept apart. However, when no hay was offered, dominant cows produced more milk and had a faster pasture biting rate when grazed together with subordinates. Cows high in the dominance order were more likely to enter the parlor first, but not to begin grazing first. The results suggest that production can increase, when dominant and subordinate cows in a competitive situation are separated and there is no benefit to separate them if they are at pasture all the day.