عنوان مقاله [English]
نویسندگان [English]چکیده [English]
A deterministic model based on milk price system in Iran is used to estimate economic weights for milk production, fat and protein percentages and herd life for Gilan indigenous cattle. Two approaches have been adopted for this estimation: maximization of profit and minimization of costs in the long run where total input is restricted and all costs are variable for cattle unit. By simulating data collected from a sample of 100 heads of cattle in Gilan province the sensitivity of these coefficients has been examined with respect to a 20 percent change (increase or decrease) in forage and concentrate prices, the cost of non food items, milk price, the average of milk production, fat and protein percentages and herd life span. The estimated economic weights of milk production, fat and protein percentages and herd life are 895, -27311, -13901 and 196.6 respectively on the basis of adopting profit maximization approach. When adopting cost minimization approach the coefficients are -1.05, 3.2, 1.6 and -6.9. A 20 percent increase in the forage price has an impact on fat and protein weights that is more than two times increase in the price of concentrate in both approaches. The ratio of economic weight of herd life to milk production is positive in both approaches and in most counties. This trait can rise the economic performance more than others and it is in the same direction as milk production trait. Results show the systems differ considerably with respect to nutritional status and its associated cost, milk production and its related expenses and type of supply arrangement. Thus the economic weight movements are not similar against the changes in production factors in different counties. In addition some of the traits have more stability than others such that for each production system a specific economic weight should be estimated.