The criteria used by farmers to assign animals to the different groups do not only concern nutritional aspects, implying that each group is not homogeneous with regards to nutrient requirements. The food intake and feeding behaviour of 12 loose-housed Charolais cows (6 dry and 6 lactating), given hay ad libitum were compared in homogeneous (Hom) and heterogeneous (Het) groups according to their physiological states: Hom groups were comprised of cows in similar physiological states (dry or lactating) and Het groups were comprised of cows in different physiological states (dry + lactating). No difference was detected in daily intake level in Hom and Het groups: 14.8 and 14.5 kg DM for dry cows, 15.4 and 15.3 for lactating cows, respectively, nor for daily time of eating: 4 h 53 and 4 h 44 for dry cows, 5 h 50 and 5 h 34 for lactating cows. In Het groups, lactating cows ate more at night: from midnight to 10.00 hours, they had already spent 2 h eating vs. 1 h 30 in Hom groups. Cows had significantly more short meals (< 1 h) in Het groups: 11.1 vs. 9.0 for dry cows and 12.4 vs. 10.6 for lactating cows in Het and Hom groups, respectively. This fractionising of the eating activity concerned particularly submissive dry cows and high producing lactating cows.
