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New York Holstein herds (1,152) including 75,875 cows were classified by housing system (stanchions, free stalls, and other combinations). Records initiated in these herds from 1964 to 1968 were used to determine the degree to which housing type might affect variance of milk production records in herds with 45 or more cows.
The within-herd variances by lactation for each housing system in each year-season were examined by Bartlett's test for nonhomogeneity among housing systems. Records in the stanchion systems were less variable than those in free-stall systems. This difference was not large enough to require adjustment for type of housing in the present production analysis procedures.