The present study was conducted on first lactation monthly test day milk yield records of 466 Holstein Friesian× Sahiwal crossbred cattle maintained at Directorate of Livestock Farms, GADVASU, Ludhiana. Four mathematical models viz. Mixed Log (MLF), Exponential (EF), Inverse Polynomial (IPF) and Polynomial Regression functions (PRF) were compared for monthly test day milk yield records. The adjusted R2 values of these functions were 88.80, 86.68, 99.90 and 99.31%, respectively; whereas the root means squares error (RMSE) with these functions were 0.161, 0.176, 0.172, and 0.035 kg, respectively. The PRF was adjusted best fit based on adjusted R2 and root mean squares error (RMSE) values. The best fit lactation curve functions will be helpful for milk yield prediction as well as genetic evaluation and selection of superior sires using records of their daughters.