The effect of protein level on the performance of dwarf and normal crossbred layers

Abstract

Dwarf and normal crossbred layers from Australorp dams by White Leghorn sires that were heterozygous for a sex-linked recessive dwarfing gene were compared at four protein levels (15, 17, 18 and 19 per cent). Relative to normal birds, dwarfs laid 19.1 per cent fewer eggs at 11.2 per cent lighter egg weight to give a reduction of 28.0 per cent in average egg mass per bird. Dwarfs consumed 28.2 per cent less feed than their normal relatives but showed no difference in the conversion of feed to eggs. Analyses of the effect of protein level of the rations, which included a wider range of protein levels than those used in the comparison of dwarfs and normals, showed that both genotypes had similar responses to increased protein level with, in general, no significant responses in production characters past a level of about 17 per cent protein.