dynamic programming

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.

The lack of efficient use of water as a production input has led to wastage of a significant amount of this input, which is financed at a great cost. Most provinces of the country have been facing water crisis for decades. Symptoms of this water crisis have been observed in some plains of Khorasan Province since the early 1970s, and this crisis has intensified in the last decade due to the lack of proper management of water resources. Therefore the present study, using a dynamic approach, studies the management of water resources in the Tabarkabad Dam in Quchan.
In this paper we put forward an easy-to-implement methodology for solving deterministic or stochastic dynamic programming problems within a standard optimization package such as GAMS. We found that the use of orthogonal polynomials was especially helpful in implementing approximation methods for the iterative computation of the infinite-horizon value function, due to their superior convergence properties over standard polynomials. This method is described using the case study of Tabarkabad Dam in Quchan city. For this purpose, data related to the Tabarkabad Dam were collected through the National Dams Information System for the years 2008-2016. Also, data relating to the estimation of the agricultural water demand function in Quchan city were obtained through a questionnaire prepared by the Ministry of Jihad-e-Agriculture.
Based on the results, comparing the actual and simulated values for the dam reservoir (state variable) and water release (control variable), it is determined that the simulations performed with orthogonal polynomial Chebyshev approximation were appropriate. Finally, based on the results, the netpresent value of water allocated to agriculture at Tabarkabad Dam in the studied period is 1471205 Rials and the allocation of water is equal to 24.745 million cubic meters per year.
Considering the results obtained and the proper approximation of simulated values, we can use the proposed method of this study to solve stochastic dynamic programming problems, especially in the field of water resource management. Also, by using the annual allocation of water and taking account of other regional constraints, we can provide a suitable cropping pattern for the sustainable use of agricultural water for the coming years in the fields covered by the Tabarkabad Dam.