Variations in Amount of Culling from D. H. I. A. Herds
S. A. Asdell · Journal of Dairy Science · 1951
The figure usually supplied was the 'average number of cows on test.'This is the sum of the monthly totals of milking and dry cows in D. H. I. A. herds divided by 12. ~rirginia reported the number of ' cow years.'This is the number of days a cow is milking divided by 365.The Wisconsin data did not show the nature of the total for that state ; it was described as a sample of 10,000 cows.Since the numbers for these states are a small portion of the grand total, no attempt was made to modify them.The grand total represents the sum of the numbers of cows on test for each year.