Optimum young bull number in Iranian Holstein under simultaneous selection for milk, fat and protein production

The objective of this study was to determine the optimum number of young bull for progeny test program in Iranian Holstein dairy cattle population with the use of deterministic simulation. Three traits including milk yield, fat and protein yield were considered as selection goal traits. In the simulated programs, number of young bulls were variable, but number of daughters per young bull was kept constant equal to 70 heads so, selection accuracy was constant, but selection intensity was different. The economic efficiency of each progeny test program was considered as the ratio of discounted return to the discounted cost. Maximum economic efficiency, genetic economic gain, discounted cost and discounted return were equal to 5.46, 416223.75, 7307144667 (Rials) and 19766307238 (Rials), respectively, which were achieved by progeny testing of 29, 93, 120 and 100 young bulls. The study of optimum progeny test economic efficiency and the young bull number per %20 changes in model’s economic parameters showed that economic efficiency had the maximum sensitivity to changes in discounted rate and milk yield economic value. %20 fluctuations in discount rate and %20 decrease in young bull purchasing and maintenance cost were led to change in progeny test structure while %20 fluctuations in other economic parameters had no effect on the structure of optimum progeny test structure.