Two comparative slaughter studies using 24 male goats and 40 Omani male sheep lambs were carried out to determine the effects of various levels of metabolisable energy (ME) on chemical composition of carcass and non-carcass portions. Eighteen goats and 30 lambs were divided randomly into four groups. Group 1 (6 goats and 10 lambs) was slaughtered at the onset of the trial, while the remaining groups were fed one of three diets containing 8.67, 9.95 or 11.22 MJ ME/kg DM from weaning until slaughter. The feeding trial continued for 141 d for goats and 123 d for sheep. Dietary energy density had a significant effect on the slaughter weight in both sheep and goats. Carcass water and fat percentages were affected significantly by the dietary energy density. Non-carcass water, protein and fat were also affected significantly by the dietary energy density. With increasing age and body weight (comparing the initial slaughter group and those slaughtered at the end of the trial), content of water, crude protein and ash decreased whereas that of fat increased in carcass portions of both goat and sheep. Goat carcasses contained more water than sheep. On a dry matter basis, goat carcasses contained significantly lower fat and ash but higher protein levels than sheep. This emphasises the ability of goats to produce leaner carcasses than sheep, which is a preferable meat characteristic to consumers. Responses to dietary energy manipulation were quite different between goats and sheep in terms of carcass and non-carcass composition as interactions between species and diet were significant.