Feeding is the predominant behavior of ruminants, as il-lustrated by the observation that feeding activity has priority over rumination whenever the causal factors of the two activi-ties conflict (Metz, 1975). Feed intake is the major factor in-fluencing milk production and body condition change during lactation. Consequently, grouping strategy and subsequent group feeding behavior that influence DMI potentially have a tremendous impact on cow productivity, animal well-being, herd health, and farm profitability. The design of the feeding system, feeding management, and dietary formulations must recognize the dynamic nature of dairy cow psychology and physiology, nutrient requirements, and variability in feedstuff composition (Sniffen et al., 1993). Improperly grouping dairy cows may perturb their normal behavioral routines and time
budgets. In essence, dairy cows spend 3 to 5 h/d eating, con-suming 9 to 14 meals per day. In addition, they ruminate 7 to 10 h/d, spend approximately 30 min/d drinking, 2 to 3 h/d being milked, and require approximately 10 h/d of lying and (or) resting time (Grant and Albright, 2000). Management de-cisions on a dairy must not interfere with the cow’s ability to perform these activities which comprise her daily routines.
Grouping should not only minimize negative social interac-tions and encourage positive interactions, but proper grouping strategy will also decrease within-group variation and increase across-group variation. A more homogeneous group of cows makes proper ration formulation easier and also decreases nutrient excretion, thus reducing the impact on the environ-ment and land use (St-Pierre and Thraen, 1999).