Date of this Version
Over 1,000 Holstein herds in New York's Dairy Herd Improvement Cooperative were classified as to housing system. The two housing systems considered were stanchions and free stalls. First-lactation records (21,285) produced in these herds by daughters sired through artificial insemination were analyzed to determine if housing system would affect sire ranking. The study covered records started in 1964 through 1967.
The sire component of variance was estimated for each housing system for deviations of these records from their adjusted herdmate averages. The covariance between the means of daughters in each housing system was computed. The genetic correlation between sire effects in the two systems was determined by dividing this covariance by the geometric mean of the sire components of variance for the two housing systems. The estimated correlation was near unity for each year of the study, indicating essentially complete agreement between sire rankings in the two housing systems.