Selective Breeding for Aggressiveness in Chickens

EXCEPT for Game breeds, the domestic fowl has not been consciously selected for behavior traits. However, poultrymen have been aware of some breed differences in behavior, especially between the so-called light and heavy breeds. Some preliminary tests with two breeds and their reciprocal crosses by the senior author (unpublished) gave good evidence of a genetic background for aggressiveness. Komai, Craig and Wearden (1959) have estimated the heritability of social aggressiveness in the domestic fowl to average near 0.30, when data for six strains were analyzed. Breed differences were observed in social dominance relations (Potter, 1949; Holabird, 1955; Tindell and Craig, 1959) and in the effects of androgen on aggressiveness (Allee and Foreman, 1955). Breed differences in the fighting behavior of cocks treated with androgen were reported by Hale (1954), and Siegel (1959) obtained significant differences between aggressiveness and sex drive among cocks of inbred lines. In the experiment reported here, …