Projecting health cost from research herds

Health costs by categories were summarized from 1,999 lactations of 863 cows in three dairy herds. These costs were projected to Dairy Herd Improvement data. Health categories were mammary, reproduction, locomotion, digestion, respiration, other, and total. The largest estimated total health cost of $67.63 was associated with postpartum length (days in milk and dry) greater than 420 days, an average 98 days dry, and milk production greater than 8,250 kg in fourth or later terminal lactations. The smallest estimated total health cost of $22.25 per lactation was associated with production between 5,750 and 6,999 kg in the nonterminal first lactation with postpartum length less than 300 days. For nonterminal first lactations of intermediate length, the estimated total health cost represented 3 to 6% of the value of milk production. First-calf heifers with milk production less than 5,750 kg and postpartum length 300 to 419 days had the least mammary cost. Cows in their fourth or later lactations with postpartum length greater than 420 days and milk production less than 5,750 kg had the highest reproductive cost. Mammary cost increased and reproductive cost decreased with increased days dry. Cows in terminal lactations had $11.38 more total health cost, $4.33 more mammary cost, and $6.31 more reproductive cost than cows in complete nonterminal lactations. Relatively more reproductive than mammary cost occurred in terminal lactations compared to nonterminal lactations. Mammary cost remained the largest component of total health cost. Multiparous cows had more total health, mammary, and reproductive costs than first parity cows. The repeatibility of total health cost was .12 +2- .03.