It is a general believe that the local sheep breed Churra da Terra Quente (CTQ), reared in the Northeast of Portugal is well adapted to the conditions of its production system. However, there are large gaps on our knowledge to allow understanding of such claimed adaptation. Splanchnic tissues (ST) can account for 35-50% of body energy expenditure, this high demand for energy being positively related with the protein and cell turnover, which in turn allows adaptability and flexibility so that animals can respond to multiple physiological and environmental challenges. The objective of the present study was to compare ST weights of lambs from CTQ and from an exotic breed (Ile de France, IF) at the same mature body weight (MBW) and fed two diets differing in roughage level. The study was carried out with 15 female lambs from each of the two breeds. Initial body weight was 20.7±1.3 and 34.0±0.7 kg, for CTQ and IF respectively, corresponding to ca 45% of their MBW. Animals were assigned to be slaughtered as an initial group or when they reached ca 65% of their MBW, after being fed ad libitum a high (HR, 70% of meadow hay) or a low-roughage diet (LR, 25% of meadow hay), according to a 2x2 factorial design. ST were removed and weighed. Per kg empty BW, CTQ had higher weights of small intestine, large intestine, liver and total ST (P