Evaluation of Culling and Replacement rate in two different optimization systems for reproductive and reproductive traits and reproductive and health traits in dairy herds

The purpose of this study was to evaluation the culling rate in two different optimization systems for reproductive and reproductive traits and reproductive and health traits in dairy herds based on data collected from dairy herds in Ardabil province according to market conditions in a production period from 2017 to 2018. One of the most important management decisions affecting livestock profit is timely replacement with young heifers. By analyzing the economic system of the dairy herd system, they were broken down into income and cost components, and each of these components was subdivided into other sub-sections. Then, using mathematical models, a simulation of a bioeconomic model was performed and optimized using MATLAB's Compecon toolbox and dynamic programming. Dairy cows were treated by status variables at three levels (low productivity, medium and high productivity) and reproductive performance at four levels (ideal calving interval, 50,100 and 150 days delay) and health performance at three conditions (no disease, The curable disease, a disease that causes involuntary eradication, was categorized and evaluated in the planning horizon with 10 lactation cycles. The results of the production and reproductive model showed that in the low-production group, the present value increased up to the fourth abdomen and then decreased. And in the intermediate group the present value is increased to the second abdomen and then decreases automatically and in the high productive group the first abdominal value decreases. The results of the production and health models were similar to those of the production and reproductive models in terms of present value changes. Future value is the value of an asset or cash at a specified future date, which is equal to the present value at a present value. It was observed that the trend of future value changes in both systems in different breeding and reproductive status and health and production status decreased with increasing lactation and with increasing cow age. The difference between the future value and the present value under the discount of 20% showed that this difference is further increased by the level of production. Regardless of the present and future value, cows are removed sooner than the optimal deadline, which leads to a decrease in the profitability of the herd. The optimum lifetime determined by dynamic programming was obtained using the Markov simulation for the reproduction and reproduction models of 4.99 years and for reproduction and health of 4.83 years, So that culling of dairy cows older than the optimum age leads to increased profitability of livestock units.