Other Diseases of Chickens 311 



fully mature bird the breast bone is completely ossified but 

 at hatching it is almost entirely cartilaginous. 



Normally the keel of the bone is straight and perpendicular 

 to the basal portion of the bone. In many individuals, 

 however, it is bent to one side or first to one side and then 

 the other forming an S-^shaped curve. Also it may be in- 

 clined at the base at an abnormal angle. 



Poultr\Tiien usually attribute these abnormalities to the 

 fact that the birds go to roost too young. They believe that 

 they are caused by the pressure of the hard roost on the soft 

 bone. About fifty years ago Rottiger ^ called attention to 

 the fact that crooked breast bones occur in chicks showing 

 retarded growth before they have ever roosted and also in 

 wild birds kept in captivity and prevented from early roost- 

 ing. He also found these malformations associated with 

 diseased conditions, especially catarrh. He believed that 

 they were due not to external pressure but to a lack of bone 

 forming elements in the diet or to a derangement of the 

 digestive apparatus which prevented the proper assimilation 

 of these elements. 



Our own experience is in accord with this view. Crooked 

 breast bones often occur in cases of malnutrition or disease 

 without reference to whether the birds have or have not 

 roosted. In utility stock the crooking of the bone in itself 

 may not be of great importance, though it lowers the sale 

 value of a bird greatly. Some good layers have crooked 

 breast bones. However, w^hen large numbers having this 

 malformation occur in the flock there is something wrong 

 w4th the feeding or care of the chicks and such mistakes 

 should be looked into and corrected. 



1 Rottiger, The Poultry World, Vol. 5, p. 298. (Translated 

 from Ztschr. f. Gegliigel u. Singvogelzucht by W. G. Todd), 1876. 



