The objective was to estimate metabolizable energy requirements for maintenance (ME_m), energy efficiency of weight gain (EEWG) and fat deposition, in Pelibuey and Katahdin ewes in Yucatan, Mexico. Eight non pregnant, non lactating, multiparous ewes, with average live weight and standard deviation of 35 ± 2 kg, were distributed in a complete randomized design with a 2 × 3 factorial arrangement, 2 breeds and 3 feed levels (100, 120 kcal of ME kg^0.75 and ad libitum), during 3 periods of 28 d each; the diet were composed of 50% ground Panicum maximum hay and 50% of a concentrate, based on corn, wheat and soybean meal, containing 2.0 Mcal/Kg⁻¹ of ME and 10% of CP. Feed intake was measured by offered-rejected daily food weighing, to asses ME intake (MEI), ewes were weighed every 14 d, to asses changes in live weight (CLW) and thickness of subcutaneous fat (SF) was measured between 12th and 13th dorsal vertebra. The EM_m was estimated by regressing values of CLW against MEI (Y = B0 + B1 × X), EEWG was estimate as gram of weight gain (WG) per Mcal of MEI. There were no differences (P > 0.05) between breeds in EM_m (110 ± 4 and 122 ± 4 kcal/kg^0.75, for Pelibuey and Katahdin; MEI [kcal/kg^0.75] = 119.748 + 0.264107 × WG, r = 0.81) and EEWG (33 ± 8 and 17 ± 8 g/Mcal of MEI, for Pelibuey and Katahdin); differences were found (P < 0.01) in average SF despite ewe breed (5.6 ± 0.2 and 4.7 ± 0.2 mm, for Pelibuey and Katahdin). There are not difference between breeds in energy requirements for maintenance and weight gain, but difference in body composition could be advantageous for Pelibuey ewes, fat reserves could be used with high efficiency for maintenance and lactation during dry season, in sheep systems in tropical Mexico.