Incidence of Mortality in Two Strains of Single Comb White Leghorn Chickens

EXPERIMENTS to determine if viability can be decreased or increased in the domestic fowl through selective breeding have been in progress at this station for several years. At the beginning of the study selected but non-pedigreed S. C. White Leghorn females were mated to pedigreed males of the same breed. From these matings, families showing either extremely high or extremely low mortality among their offspring were selected. These represent the high and low mortality strains referred to in this paper. Selection within the strains continued each year with the object of increasing the viability of the birds in one strain and decreasing the viability of those in the other. All chicks hatched from the birds in this project were kept for the first eight weeks. At that time the cockerels were separated from the pullets. These were later marketed except for a few that were retained as breeders. The pullets . . .