In this study, our aim was to compare estimated metabolizable energy (ME) and net energy lactation (NEL) contents in dried alfalfa samples in their different growth stages, using models such as NRC-2001, HohenheimMenke and University of California at Davis (UC Davis). A total of 73 alfalfa hay samples obtained during three different growth stages (Vegetative, Bud and Bloom) were used. Chemical analyses were performed for each sample. Energy values of the alfalfa hay samples were calculated with NRC-2001 equations from chemical analysis results, and with HohenheimMenke and UC Davis equations from in vitro gas production volumes. Gas production in alfalfa samples in vegetative period (S1) was higher than other periods (P<0.001). Again, ME values calculated with all three methods in the alfalfa hay samples of this period were significantly higher than the samples in bud and bloom periods (P<0.001). In addition, energy values obtained with HohenheimMenke equation in all periods were found to be higher than the averages obtained with NRC-2001 and UC Davis equations. It is concluded that, for the alfalfas in vegetative period, a correlation of 85.6% between energy values obtained with NRC-2001 and HohenheimMenke equations, a correlation of 81.8% between energy values obtained with UC Davis and NRC-2001 equations, and over 99% correlation between energy values obtained with HohenheimMenke and UC Davis equations were determined (P<0.000).