Chondrodystrophy in Rhode Island Reds

Abstract

This abnormality appeared for the first time in this flock in the offspring of one mating pen consisting of 10 [female][female] mated to 1 [male] that was a full brother to 2 and a half brother to 8 of the [female][female]. 7 [female][female] gave 172 normal to 54 abnormal offspring. 3 [female][female] gave no abnormal offspring. The abnormality appeared to depend on a single recessive gene since all parents were normal in appearance. The character behaved as a lethal when homozygous and was partially lethal in heterozygous progeny. The morph. characters exhibited by chicks having the abnormality were very uniform. The head was short and flat with both mandibles greatly shortened to produce very blunt beaks that did not open readily to take food and water. The shape was normal, except for being very short. No evidence of "parrot beak" was observed. Long bones of both upper and lower limbs were much shortened with some thickening in humerus and ulna and extreme thickening in the tarsometatarsus. The femur was very crumbly and lacked a complete periosteum. All long bones were straight. In body \vt. chicks were almost normal.