The aim of the present research was to study the relationship between the femur and gestational age and thus generate an equation which would be able to estimate fetal age in cows. 23 dairy cows were examined every after one week transrectally using B−mode real−time ultrasound scanner with a 7.5MHz linear probe (Mindray DP 6600, Mindray Szechuan, China). The dairy cows were examined at Large Animal Research Unit of Massey University New Zealand between day 60 and day 120 of pregnancy. Ultrasonography examination commenced the 20th of July 2015 and was finished in September 2015. The predicted gestation age in dairy cows had a chance of being 21.7 days greater and 21.6 days less than actual gestational age. The findings from this study show there is a moderate positive linear correlation between femur length and gestational age in the dairy cows (R2 =0.64). However, this relation did not have good agreement to justify the use of equation developed to be used in estimation of gestational age.