Unexpected results when assessing underlying aggressiveness in Japanese quail using photocastrated stimulus birds.

JACKELYN KEMBRO; RAUL MARIN; MARTIN CALIVA; DIEGO A. GUZMÁN; STEFANIA PELLEGRINI

Orlando

Congreso; Poultry Science Association 106th Annual Meeting; 2017

Poultry Science Association

Aggressive behaviors can affect both animal welfare and productivity.Because the expression of aggressive behaviors is dependent on thequality of the opponent, they reflect relative rather than absolute levelsof underlying aggressiveness. This study was aimed to characterizethe aggressive responsiveness of photostimulated adult Japanese quail(16 wk old) when interacting with a photocastrated (6:18h light:darkphotoperiod) counterpart in a novel test environment. This was basedon the assumption that photocastrated birds will not actively provokean aggressive confrontation. Birds were reared in male-female pairs.Frequencies of aggressive behaviors (i.e., pecks, threats, chases) weredetermined during 10 min social interactions in a novel environment.A first experiment evaluated 78 encounters between a photostimulatedmale or female with either a photocastrated male or female (photocastrationstarted at 11 wk of age). A wide variety frequency of aggressivebehaviors was observed and in general, highly aggressive birds receivedlittle or no aggression from their opponent. However, unexpectedly,we also found that 37 and 32% of photocastrated males and females,respectively, performed aggressions toward their photostimulatedcounterparts, and even a similar number of photocastrated and photostimulatedmales initiated the aggressive interactions (Proportion test;P > 0.05). The higher aggressiveness in the photocastrated birds wasattributed to their social experience before photocastration. Therefore, asecond experiment evaluated 53 encounters between a photostimulatedmale or female and a naive photocastrated male (photocastration startedat 4 wk of age, before sexual development). In this trial, photocastratedmales performed no aggression toward their photostimulated counterparts.Consistently with previous studies, our findings show that naivephotocastrated males can be used as a non-aggressive stimulus duringa social interaction aimed to assess expression of aggressiveness inphotostimulated birds. However, caution should be taken when applyingthe photocastration protocol considering that prior fighting and sexualexperience or other physiological changes related to maturation caninterfere during subsequent aggressive testing.