Dwarfism in Diverse Genetic Backgrounds: Diet-Egg Production Relationships

The effect of diet on phenotypic expressions of the sex-linked dwarf gene, dw, was studied in lines of chickens selected for high and for low juvenile body weight. The relative reduction of body weight and shank length due to dw was consistently greater in the low-weight than in the high-weight line regardless of diet. The hen-day egg production of high-weight dwarf pullets was greater than that of their normal siblings while the opposite relationship was found in the low-weight line. Feeding a diet containing increased levels of protein, calcium, phosphorus, and metabolizable energy increased the egg production of dwarf pullets, regardless of their background genome, but did not significantly affect the egg production of normal pullets. This diet also partially prevented the reduction in shell thickness associated with dwarfism in the low-weight line. In addition, the tendency of dw to reduce the incidence of defective eggs in the high-weight line and to increase the incidence of the low-weight line varied with diet. Dwarf pullets of both rapid and slow growing populations require different diets for the maximum realization of their genetic potential.