|Dennis, Rachel -|
|Cheng, Heng Wei|
Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 6, 2011
Publication Date: November 1, 2011
Citation: Dennis, R.L., Cheng, H. 2011. The dopaminergic system and aggression in laying hens. Poultry Science. 90:2440-2448. Interpretive Summary: Aggression and cannibalistic pecking in laying hens presents a serious welfare concern for the hens as well as an economic hardship to the producer. Currently the detrimental and harmful effects of these behaviors are lessened through beak trimming, a practice that also has the potential to cause pain and reduce animal well-being. Breeders are attempting to breed hens with reduced pecking behaviors; however, due to a limited understanding of the genetic mechanisms mediating aggression they have met with limited success. This study was designed to better understand the heritable differences in neurochemical mediation of aggression between high and low aggressive strains of laying hens. Our data show evidence of heritable differences in neurotransmitter regulation of aggression in chickens. The data from the present study can be used by breeders, producers in management practices and other scientists when planning or interpreting their studies.
Technical Abstract: Aggression and pecking behavior in laying hens is a serious concern to the production and well-being of the hens. Current breeding programs attempt to reduce aggression in hens without altering production have had limited success. Improved understanding of the neural mediation of aggression, will better allow for more efficient breeding of layer hens through selection against aggressive behaviors. In the present study we investigated the effects of antagonism of serotonin (5-HT) 1A and 1B and dopamine (DA) D1 and D2 receptors on aggressive behaviors and central neurotransmitter response in dominant hens of high (DXL and LGPS) and low aggressive (HGPS) strains. Aggression was decreased and hypothalamic 5-HT and epinephrine were elevated in hens from all strains treated with D2 receptor antagonist (P<0.05). Antagonism of the D1, 5-HT1A, and 5-HT1B receptors elicited different behavioral and neurotransmitter responses based on the aggressive phenotype of the genetic strain. Aggressive strains DXL and LGPS decreased aggressiveness following antagonism of the D1 receptor (P<0.05). Antagonism of 5-HT1A receptor increased aggressiveness in DXL strain only (P<0.05), while 5-HT1B receptor antagonism caused a decrease in aggressiveness in the low aggressive HGPS strain (P<0.05). Our data provide evidence of heritable differences in dopaminergic and serotonergic mediation of aggression in chickens.