Dr. Ian Duncan continues to study male aggression in broiler breeders, a problem that appears to be on the increase. His lab initiated a study to look at the effects of genetic strain and feed restriction on male aggression. Two broiler breeder strains and one commercial laying strain of males were tested with a restricted versus an ad-libitum feeding regime. Their data indicated that male aggression was not the result of feeding regime but rather genetic factors apparent in most broiler breeder males
A further study looked at overall aggression of broiler breeder males. Males were compared to a Game strain as well as to a laying strain of males under similar conditions. Aggressiveness toward a male model was also observed. The researchers concluded from their study that aggressiveness of the broiler breeder strain being tested was not due to it being more aggressive since it did not act as aggressively to a male model as did the Game strain males. An additional study looked at female receptiveness to male courtship advances. If females tend to avoid male courtship this could possibly trigger frustration in otherwise normal males. A number of females were tested in a specific maze system where they had a choice between a broiler male and a laying strain male. It was concluded from the study that females do use male behavior as a basis for their choice of males and not male appearance. Broiler breeders males were found to be deficient in some elements of courtship behaviour. In practice, this means that females are much less likely to crouch when broiler breeder males approach them and this, in turn, leads to the males chasing the females and forcing themselves on them.
Male aggression in broiler breeder flocks leads to increased bird mortality and also reduced fertility in a flock. Since a significant percentage of the approximately 10% of non-fertile eggs, resulting from the average commercial flock, can be the result of male, female negative interaction, further research into obtaining a 1 to 2% increase in fertile eggs from a flock would be a worthwhile research investment in this type of study.