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The present investigation was carried out using data of first lactation monthly test day milk yields (MTDMY) of 191 Murrah buffaloes maintained at Govt. Livestock Farm (GLF), Hisar and Livestock Research Centre (LRC), Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut over a period of 12 years (2003 to 2014). The data were classified according to season, period and age groups to study the effect of non- genetic factors. The mean of MTDMY increased from 4.625±0.145 kg on MTDMY11 to a peak yield of 10.636±0.214 kg MTDMY3 for first lactation. The season of calving had highly significant (P˂0.01) effect on first lactation MTDMY viz. TD1, TD2, TD3 and TD4 in first lactation. However, significant (P˂0.05) effect was found on MTDMY viz. TD5, TD6 and TD7, whereas non significant effect was observed on all remaining monthly test day milk yields. The effect of period of calving on monthly test day yields was highly significant (P˂0.01) on TD2, TD3 and TD7, while significant (P˂0.05) effects was observed on TD1, TD4, TD5 and TD8 monthly test day milk yields. The effect of period of calving on all remaining monthly test day yields was non-significant. The age groups had significant (P˂0.05) effect on TD2 and TD3, whereas non-significant effect on rest of the monthly test day milk yields was observed.