ESTIMATION OF THE ECONOMIC VALUE OF CONCEPTION RATE IN DAIRY-CATTLE

The economic value of fertility in dairy cattle was estimated using dynamic programming. The expected future cash flow of a cow, given the average conception rate of the herd, was determined and maximized with a model similar to that of van Arendonk, which was used to optimize the replacement policy. The marginal cost of a decrease in fertility in the herd was then estimated as the ratio of the difference between the expected cash flow of a heifer at calving to the difference of respective average conception rates in the herd. The estimated result was a minimum value but took into account all the consequences of a change in fertility, i.e. on culling rate, on the current and each subsequent lactation and on immediate costs. In the present French conditions, the marginal value of 1% absolute change in conception rate was estimated to be between 10 and 20 FF. This value decreased when the average fertility level increased or when the conditions for culling and replacement were more favourable, i.e. when the culling value was high or the replacement costs were low. © 1990.