A total 159 milk samples from NDRI herd were collected for analysis of milk compositions. Milk compositions were determined by Lacto Star apparatus and Pyne's method. The objective of the present investigation was to assess the effect of non-genetic factors on test day milk yield and constituent traits, and least-square analysis was used for analysis. Overall least-squares means for TDMY(kg), fat%, protein%, SNF%, TS%, casein% and casein protein ratio were 8.62±0.36, 5.15±0.07, 3.71±0.02, 9.92±0.04, 5.34±0.03, 15.01 ±0.09, 2.85±0.02 and 0.767±0.002, respectively. ANOVA revealed that the differences were statistically significant for non-genetic factors on some of the constituent traits.