Use of System Dynamics to Evaluate Shortening of the Calving-to-Conception Interval in Japanese Black Cattle

Abstract

Beef cattle numbers in Japan are decreasing with the loss of farmers. Improvement of productivity is necessary to allow the remaining farmers to stabilize cattle production and management. The calving-to-conception interval, which has increased in recent years, must be reduced. We made a system dynamics model to evaluate the improvement of productivity by reducing the calving-to-conception interval. The model focuses on the growing stage and sets an upper limit to the number of cows. Our simulation reduced the interval from calving to first service from the default 80 days to 60 or 70 days, and the number of artificial inseminations from the default 1.6 to 1.0 or 1.3. For every 1 day reduction of the calving-to-conception interval, a farm with 100 head of cattle would increase the annual number of calves by 0.23, increasing its profit by 128,000 JPY.