Changes in Milk Production in Relation to Changes in Feeding and Management Practices in Dairy Herd Improvement Association Herds

All Holstein herds of over 20 cows which had automated data processed dairy herd improvement association (DHIA) records from Cornell laboratory for two consecutive years from 1960 to 1964 were used to determine production, feeding, and management changes. The average number of herds for the four 2-yr comparisons was 2,688, 60% in New York and the remainder in neighboring states. Results in the two locations agreed. The yearly changes and standard deviations of changes per cow for the New York herds were milk production, + 157 ± 400 kg; grain feeding, + 88 ± 241 kg; succulent forage, + 0.13 ± 1.76 metric ton; dry forage, - 0.04 ± 0.50 metric ton; net energy from pasture, - 0.60 ± 6.10%; herd size, + 1.8 ± 5.65 cows; days in milk, + 0.24 ± 2.93%. Only two factors were closely correlated with change in milk production - change in grain fed and change in per cent days in milk. Multiple regression analysis, using the six factors above, indicated that a change of I kg in grain feeding resulted in a change of 0.84 kg of milk and a 1% change in days in milk gave a change of 45 kg of milk