The study investigated the effect of forage type on maintenance energy (ME_m, MJ/kg BW^0.75 per day) requirement and the efficiency of utilization of metabolizable energy intake for milk production (k_l). A database containing 652 observations was assembled from calorimetry studies. The data was subdivided into six sets. These were grass silage 1, maize silage 2, fresh grass 3, mixed silage 4, dried grass 5, and straw 6, based diets. Meta-analysis estimated the values of ME_m and k_l to be 0.54, 0.56, 0.56, 0.60, 0.72, 0.59, 0.54, 0.58, 0.55, 0.58 and 0.61, 0.60 for subsets 1-6, respectively. There was no significant difference in the estimate of fasting heat production (FHP) in all subsets except fresh grass. This resulted in a significant difference in ME_m when compared to cows fed other diets. Although differences in k_l were observed when data were fitted with fixed FHP, unconstrained fitting showed that k_l was about 59%.