Deriving Economic Values for Female Reproductive Traits in Lifetime Carcass Production of Japanese Black Cows Using Deterministic Profit Function

Improving reproductive efficiency is required to strengthen the production base of high-quality Wagyu beef in Japan. We developed a deterministic profit function (P) for lifetime carcass production of Japanese Black cows to calculate economic values (EVs) for representative female reproductive and carcass traits. The total calving number per cow was expressed using the age at first calving (AFC) and calving interval (CI). Revenues and costs were calculated from calf market price (CaP) and carcass unit price (CUP). A cubic regression equation was developed with CaP as the response variable and calf market weight as the explanatory variable. A multiple linear regression equation was developed with CUP as the response variable and five carcass traits as explanatory variables. EVs were calculated using the first-order partial derivatives of P. The first-order partial derivative of CI was a function of CI with the quadratic term of CI in the denominator. Values of EVs for AFC and CI were negative, suggesting that earlier AFC and shorter CI increase the lifetime profit of Japanese Black cows through producing higher numbers of feeder cattle per cow. However, this might bring benefit to only calf-producing farmers. The results would contribute to achieving sustainable high-quality Wagyu beef production.