Investigation of the effect of certain paragenetic factors on fertility traits of bull dams of Simmental breed

Investigation included bull dams of Simmental breed selected on farms of agricultural producers on the territory of the Republic of Serbia. Method of Least Squares - LSMLMW (Harvey 1987) was used for analysis of the effect of region and order of lactation on reproductive traits. Obtained results indicate the justification for investigation of paragenetic factors, since the knowledge of their effect can contribute to more objective evaluation of random effects. Regions had highly significant effect (P 0.05). The effect of region of breeding many factors are included and most important one is nutrition. Order of lactation as second factor investigated in this research had no effect on any of the fertility traits (p>0.05). General average of mean values of least squares for fertility was: for age at first conception 517.61 days, duration of pregnancy 285.51 days, duration of service period 108.98 days, interval between calving 395.34 days.