Ostrich belongs to ratites bird flock. In spite of most morphological similarities of this bird to other birds, there are some differences between them. Large intestine of brids consists of a pair of cecum and a straight short intestine called rectum. In many bird flock, cecums in the form of two right and left closed- base tubes originate from junction of rectum and jejunum. Shape and size of large intestines are very variables. For this study, 36 ostrich chicks from east Africa breed (Struthio camelus, massaicus naumann) were selected randomly in 6 groups, each group having 6 chicks (three male and three female) by different ages. Colon and cecums were observed carefully in terms of colour, size, and proximity, and they were measured three times by digital calipers. Cervix width of cecum was more than width of ileum and colon origin. Inner duct of two right and left cecums with a common pore were opening into colon from back side. About 24-32 annular lines were apparent on external surface of both right and left cecums. Diameter of these rings was shorter than cecum diameter at the same point and it caused both cecum to have saccular state. Plica circulares were located on the internal surface of lumen of both cecums. The number of these plica was equal to the number of annular lines of cecum external surface. There were concave annular lines on external surface of chicks' colon. These appeared from the beginning of colon and extended to middle part of it. Shorter diameter of these rings compared with normal diameter of colon had caused initial and middle parts of colon to be observed as saccular state on the outside. Plica circulares were observed on the internal surface of lumen. These plica circulares were located inside just opposite to external rings of colon. Their number was equal to external rings. In the nearest species such as Rea, secum is relatively long and plica circulares have less compared with ostrich. Secums of Amo and casovari have been developed slightly and they are passive and have saccular structures on external surfaces. In kiwi brid, cecum is large and wide. Saccularation of cecum of this bird is less than ostrich, and cecums with two lateral pores open into colon. Trugopan satyra is they only bird of fowl which has apparently saccular cecum. Depending on diet and colon size, cecum varies in birds. In casovari, condsidering relative size of body, they length of colon is shorter than that of ostrich, but Rea bird has a long colon. Screamer has a large and twisty colon. Ostrich which is a bird with high-fibre diet, has a very large colon and cecum, plica circulares inside their lumen causes facies contactus to increase by fibrous foods.
