HYPER-AGGRESSIVENESS IN MALE BROILER BREEDER FOWL

Suzanne T. Millman, Ian J.H. Duncan and Tina M.Widowski University of Guelph, Guelph, Ontario.

Concerns have been raised by the broiler breeder industry regarding increased levels of aggression in males of certain strains. Males have been reported to savage and even kill females. Our previous work indicated that broiler breeder males were deficient in courtship behaviour and forced copulations more frequently than did commercial laying strain males. To investigate the problem of high levels of aggression, a 3x2 factorial was used to compare males of 3 genetic strains (2 broiler breeder lines and 1 commercial laying strain) at 2 feeding levels (restricted and ad libitum) during the breeding phase. All birds were reared according to the management guidelines for each strain. At 22 weeks of age, 12 pairs of males per strain were each penned with 20 females of a broiler breeder strain. Behaviour was sampled from each pen for six 10-minute periods at weeks 25, 27, 29, 33 and 37. Results indicated that broiler breeder males performed significantly more aggressive behaviour than did laying strains males (P<0.0001). As behaviour was not found to change significantly over time, data was pooled across age. Mean incidences of aggressive behaviour directed at males per 10 minute period were 0.24+/-0.03, 0.52+/-0.06 and 0.49+/-0.05 for the laying strain and broiler breeder strains A and B respectively. Full fed males were significantly more aggressive toward males than were restricted males (P<0.0001). Broiler breeder males showed more aggressive pecking directed at females than did laying strain males, with mean incidences per 10 minute period of 0.09+/-0.02, 0.85+/-0.12 and 0.53+/-0.06 for the laying strain and broiler breeder strains A and B respectively (P<0.0001). From this study, broiler breeder males were found to be more aggressive toward males and extremely aggressive toward females when compared with commercial laying strain males. Full fed males were the most aggressive. Few significant differences were found between the two broiler breeder strains.