Abstract: Five faunated and five defaunated sheep were fed diet containing 70:30 concentrate to roughage (oat hay) ratio and energy balances were determined by carbon and nitrogen balance method.Intake and nutritive value of the diet did not differ between faunated and defaunated sheep. Loss of carbon in urine and methane as percent of intake was significantly (p<0.01) less in defaunated sheep but energy balance and efficiency of utilisation of ME for maintenance was similar in both faunated and defaunated animals. The energy cost per g protein and fat synthesis in defaunated sheep was 13.9 and 12.3 kcal ME, respectively. It was inferred that high concentrate to roughage ratio and maintenance type roughage like oat hay in ration of defaunated Muzaffarnagari sheep does not yield any additional benefit from energetic point of view, compared to faunated sheep.