The aim of the present study was to obtain relevant results related to the basic indicators of fertility and milk yield of Simmental cows, in production conditions on farms of agricultural producers, using appropriate mathematical and statistical procedures, i.e. to determine the influence of bull sires originating from Serbia, Austria and Germany on the implementation of the main breeding program and improvement of production traits of Simmental cows on the territory of Šumadija district. The study of the effect of bull sires who are originally from Serbia, Austria and Germany on performance traits of Simmental cows included a total of 303 cows in first three lactations. Milk production of cows descendents of bulls from the German population was higher compared with the production of cows originating from Austria in the first lactation by 58.29 kg and in the third by 67.72 kg, but in the second it was lower by 12.31 kg. The variability of age at first calving ranged from 766.93 (cows progeny of domestic bulls) to 813.06 days (cows progeny Austrian bulls). Average duration of service period had the interval of variation of 86.80 in cows from domestic bulls in the third lactation to 109.88 days in cows originating from Austrian bulls in the first lactation
