Evaluation of Criteria Used to Group Lactating Cows Using a Dairy Production Model

¹ Agricultural Research Service, USDA, Roman L. Hruska US Meat Animal Research Center, Clay Center, NE 68933
² Department of Animal Science, Cornell University, Ithaca, NY 14853

A dairy herd production simulation model was used to evaluate the effectiveness of seven grouping strategies in terms of annual income over feed cost per cow. The strategies (1 to 7) were characterized by the criteria used to rank individual lactating cows for placement into feeding groups: 1, required nutrients (energy and protein) per kilogram of DMI; 2, required nutrients (energy and protein) per kilogram of NDF intake capacity; 3, DIM; 4, test day milk; 5, test day FCM; 6, dairy merit (kilograms of FCM per kilogram of BW^.75); and 7, dairy merit weighted by DIM. In terms of annual income over feed cost per cow, strategies 1 and 2 were found to be the most effective and strategy 4 the least effective, with average potential production levels of 8000, 9000, and 10,000 kg of milk per 305-d lactation, using two of three feeding groups. With the milk-feed price relationships used, mean annual income over feed cost per cow for grouping strategies 1 and 2 with three feeding groups was $21, $33, and $40 geater than with two feeding groups for potential production levels of 8000, 9000, and 10,000 kg of milk per 305-d lactation, respectively.

Key Words: grouping criteria • computer model • dairy

Submitted on November 19, 1990
Accepted on July 24, 1991