Bovine mastitis and optimal disease management: Dynamic programming analysis.

Wise decision-making for coping with infectious diseases is a key to the success of farming, agriculture, as well as public health. Mastitis of dairy cows causes large economic burden to dairy farmers. Here, we study the optimal operation for a dairy farmer to manage cows infected by mastitis. In the simple model, we considered cows with different number of breasts (quarters) infected by mastitis. In the detailed model, we considered additional complexities: a cow produces milk only after the first birth of a calf, old cows are culled, milking is not practiced for 10 weeks prior to expected calf-birth, and a newborn calf provides an economic benefit. By fitting the parameters to the Japanese dairy farming situation, the dynamic programming analysis reveals whether an infected cow should receive medical treatment depends on the number of breasts infected, age, and season. Cows should be culled if many breasts are infected, they are old, and it is not close to the next calf-birth. The optimal management policy depends critically on milk price, maintenance cost, and recovery rate from mastitis infection, but not on infection rate.