The Results of Selection Against Expression of the "Short Upper Beak" Mutation in Fowl

Abstract

Breeding experiments in which selection was exercised against the lethal action of and the production of beak defects by the "short upper beak" mutation of fowl yielded the following results. The percentage of hatched chicks became nearly normal. In the final progeny the great majority of chicks had a normal beak at hatching time, and most of those chicks which at first had a slight shortening of the upper beak became normal during growth. In some instances the upper beak at maturity was longer than normal. The effect of the "short upper beak" mutation on long bone length became lessened under the influence of selection against lethal action and beak deformity. The "short upper beak" mutation was found in Houdan stock. The modifiers of this mutation were picked up after outcrosses to White Leghorn fowl. It is concluded that the "modifiers" are part of the normal genic make-up of beak development in the White Leghorn breed.