To compare the energy estimates of mixed diets obtained from rumen in vitro incubation for gas production (RIVIGP) and digestion trial (DT) in NariSuwarna x Kenguri F1 sheep, twenty four sheep were divided into six groups of five each. Six mixed diets were prepared by using sugarcane trash and concentrate feed mixture in the ratio of T-1 80:20, T-2 70:30, T-3 60:40, T-4 50:50, T-5 40:60 and T-6 30:70 2,3,4, 5 and 6 were 6.7, 6.9, 7.4, 7.2, 7.8 and 9.4 respectively. The corresponding ME values obtained from RIVIGP were 5.3, 5.9, 6.2, 7.5, 8.6 and 9.4 respectively. The difference between the ME obtained from DT (digestion trial) and ME predicted from RIVIGPT was found to be 10.7 per cent. The mean ME output (Maintenance + weight gain) for the diets-1, 2, 3, 4, 5 and 6 were 6.37, 6.34, 7.38, 7.70, 8.06 and 8.27 respectively. The ME intake estimated from ME obtained from DT and RIVIGP for the diets-1, 2, 3, 4, 5 and 6 were 4.91 and 3.79, 5.02 and 4.22, 7.63 and 6.46, 7.74 and 8.13, 8.76 and 9.81, 11.42 and 11.85 IntroductionThe metabolisable energy content of feed or diets were estimated by conducting digestion trial in animals.