Sniffen et al. (1993) reviewed research that evaluated optimal group numbers on a dairy farm. Shifting a herd from one to two groups of cows increased FCM production by 1 to 3%. Moving to three groups improved FCM production by up to 2% versus two groups, but shifting to four groups from three only resulted in a 0 to 1% increase in FCM. Overall, marginal return to additional groups declined beyond three. Most researchers have concluded that the milking herd should be divided into three groups with three different diets for optimal efficiency (Grant and Albright, 1997). The actual grouping
system selected will depend on herd size, facilities available, and other specifics of the farm situation. The minimum number of groups for a herd would be two: a milking plus a dry cow group. Nutritionally, three feeding or production groups plus two dry cow groups are often preferable. A fresh cow group for the first 3 wk of lactation can serve as a transition from the dry to high-milk production groups.