Data of 3943 fortnightly test day milk yield (FTD¬MY) records during first lactation of 208 Rathi cattle calved during 1985-2014 at the Livestock Research Station, Nohar were used in the present investigation. The least squares means of the FTDMYs ranged from 3.85 kg to 8.4 kg. The relative efficiency of four lactation curve models viz. Exponential function, Parabolic function, Inverse Polynomial function and Gamma function were compared. Inverse polynomial function described the highest coefficient of determination (R2 = 99.92%) and with least value (0.0604 kg) of root mean squares error (RMSE), suggesting inverse polynomial function being best mathematical model for prediction of fortnightly test day milk yields in Rathi Cattle.