Strain differences in aggressiveness of male domestic fowl in response to a male model

The objective of this experiment was to determine if the unusually high lev els of aggression shown by male broiler breeder domestic fowl towards femal es is due to a higher overall level of aggressiveness in this strain. We co mpared the aggressive behaviour of broiler breeder (BR) males with that of males of an Old English Game strain (GA) which had been bred for fighting. Also, by rearing males of a commercial laying strain (LR) under the same le vel of feed restriction recommended for broiler breeder males, we examined the effects of feed restriction during rearing on aggressive behaviour at m aturity. Full-fed commercial laying strain (LA) males were used as a contro l. The behaviour of individual males, nine from each treatment group, towar ds a model of a male conspecific was recorded for 15 min. The test was repe ated 4 weeks later, after the males had received some limited sexual experi ence. Game strain males reacted most aggressively to the model, waltzing (P < 0.001) and crowing (P < 0.05) more than males from the other treatment g roups which did not differ significantly from each other. Waltzing and crow ing also increased significantly from the first to the second test in GA ma les (P < 0.005), but not in males from the other treatment groups. Frequenc y and duration of ground pecking was significantly less in BR males than in GA or LA males (P < 0.005) and significantly less in GA and LA males than in LR males (P < 0.05). Frequency of wing flapping was significantly greate r in BR and LR males than in GA or LA males (P < 0.005). In conclusion, bro iler breeder males did not behave aggressively towards a male model relativ e to game strain males. Whereas feed restriction during the rearing phase d id affect behaviour of adult males, aggressiveness towards a male model did not increase. (C) 2000 Elsevier Science B.V. All rights reserved.