Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/12/2004
Publication Date: 7/12/2004
Citation: Dennis, R., Zhang, H., Bacon, L.D., Esteves, I., Cheng, H. 2004. Behavioral and physiological features of chickens diversely selected for resistance to avian disease. 1. Selected inbred lines differ for behavioral and physical responses to social stress. Poultry Science. 83(9):1489. Interpretive Summary: Chronic social stress in chickens reared in high-density environments, such as a battery cage system, may be a major problem in the modern poultry industry since social stress has a large impact in both chickens' welfare and performance. An inability of chickens to adapt to their social environment results in a greater susceptibility to disease and increases the frequency of hostile behaviors, such as cannibalism, aggression, and feather pecking. The present study using genetically selected chickens has revealed that selection of chickens for greater resistance to pathogen infections associated with less aggressive behavior is one solution to improve animal well-being. The method could be adapted by producers to improve chicken well-being and reduce mortality resulting from social stress, and the method can be used by other scientist in their farm animal research to develop strains with specific characteristics.
Technical Abstract: To test the hypothesis that genetic variations in response to social stress modulate susceptibility to disease in poultry, we measured social stress-induced aggressive behaviors in chickens of different inbred lines selected for disease resistance or susceptibility as well as two recombinant congenic strains. At 15 wk of age, roosters from each genetic line or strain were randomly assigned to pairs for intraline male-male aggression tests (n = 8/ per line). Based on the results of the intraline aggression tests, the roosters were divided into two groups, winners and losers. At 16 wk of age, the roosters were randomly paired as winners vs. winners and losers vs. losers for interline aggression tests, i.e., lines 63 vs. 72 and 15I5; 73 vs. 15I5; and strain X vs. B. Similarly, at 17 wk of age, lines 63 vs. strains X and B; and 72 vs. stains X and B were tested. The tests were conducted in a novel cage that was similar to their home cage, to provide a neutral space for both roosters being tested. Each pair was video taped for fifteen minutes. Aggressive behaviors were analyzed using the Nodlus Observer. Male-male interaction-induced aggressive behaviors were markedly different among the genetic lines. Compared to roosters of lines 15I5 and 72, line 63 roosters generally showed lower aggressive behaviors including aggressive pecks and fights as well as durations (P<0.05). Roosters of the recombinant congenic stains X and B, each possess a unique random 87.5% genome of line 63, also exhibited low aggressive behaviors which were similar or equal to the level of line 63 in both intraline and interline aggression tests (P=0.05). These results may indicate that some of the gene(s) commonly carried between strains X and B as well as line 63 likely played an important role in governing their lower levels of aggression. The impact of differential social stress-induced aggressiveness in each line's unique disease resistance has been discussed. The results suggest that the present chicken lines may provide a valuable animal model for investigating the effects of genetic-environmental interactions on the behavioral and physiological homeostasis in response to stress and disease.