Screening of the Behavioral Tests for Monitoring Agonistic Behavior of Layer Chicks

Abstract

Chicken agonistic behavior, a type of social behavior related to threatening and fighting, is among the most serious problems in the poultry industry. However, due to luck of effective models for investigating the brain mechanisms of the behavior, no effective measures have been taken. This study, therefore, aimed to select the behavioral tests available for monitoring chicken agonistic behavior. Two behavioral tests, resident-intruder (R-I) test and social interaction (SI) test, were performed for 10 minutes in 10 pairs of male layer chicks at 8, 12, 16, 20, and 24 days of age, and total agonistic frequencies (TAF: Sum of the frequencies of agonistic displays like pecking, biting, kicking, threatening, and leaping) and latency (the period of time from the beginning of the behavioral test to the occurrence of the first agonistic behavior) were measured as indices of agonistic behavior. Two-way repeated measures ANOVA revealed significant differences in TAF and latency between aggressors and opponents in both the behavioral tests. In the R-I test, the TAF of aggressors significantly increased from 8 to 20 days of age, and the latency significantly decreased from 8 to 24 days of age. In the SI test, however, the TAF of aggressors significantly increased and the latency significantly decreased only from 16 to 20 days of age. When the criterion of high agonistic behavior was defined as the TAF, where aggressors showed more than 30 times of TAF and the opponents did less than one-third TAF of aggressors, the aggression establishment rate (AER), which is equal to the number of aggressors showing high agonistic behavior per total behavioral trials, was significantly higher in the R-I test than in the SI test. These results suggest that the R-I test, rather than the SI test, is an effective tool for monitoring agonistic behavior of layer chicks.

Effects of Testicular and Non-Testicular Testosterone on Territorial and Isolation-induced Aggressive Behavior of Male Layer Chicks

“…The R-I test was performed at 29 and 30 days of age and the SI test at 31 and 32 days of age. The TAFs and AER were calculated according to the protocols of Raihan et al (2017) and Yan et al (2019). The TAFs are defined as the sum of the frequencies of pecking, biting, kicking, threatening, and leaping.…”

“…In general, the R-I test is used to monitor territorial aggression induced by invasion of another conspecific to the experimental territory of an animal (Koolhaas et al, 2013), and the SI test is used to study social behavior between two animals, such as sniffing, grooming, and isolation-induced aggressive behavior (Silverman et al, 2010). In our behavioral trials, the resident chicks in the R-I test showed aggressive behavior more frequently than the intruder ones from eight days of age (Raihan et al, 2017). These s results suggest that territorial aggression in chickens is T-independent, because the plasma concentration of T in male chicks is reported to be low until 28 days of age (Tanabe et al, 1979).…”

“…In order to establish effective behavioral models that quantitatively monitor chicken aggressive behavior, we observed the aggressive behavior of male layer chicks using the resident-intruder (R-I) and social interaction (SI) tests (Raihan et al, 2017). In general, the R-I test is used to monitor territorial aggression induced by invasion of another conspecific to the experimental territory of an animal (Koolhaas et al, 2013), and the SI test is used to study social behavior between two animals, such as sniffing, grooming, and isolation-induced aggressive behavior (Silverman et al, 2010).…”

Blood Testosterone Concentration and Testosterone-induced Aggressive Behavior in Male Layer Chicks: Comparison between Isolated- and Grouped-Raising

“…The SI test was performed with 32-day-old male layer chicks as described by Raihan et al (2017). After measuring body weight with an electronic scale (HF-2000, A&D Co. Ltd., Tokyo, Japan), a pair of chicks, T-implanted (as an aggressor) and intact (as an opponent), were simultaneously transferred by hand to the diagonal corners of the observation cage (44×30×24 cm, length×width×height), and aggressive behavior of the aggressor and opponent was recorded using a video camera (GZ-R470, JVC KENWOOD Corporation, Kanagawa, Japan).…”

“…The R-I test is used to study the territorial aggression induced by intrusion of another conspecific to the experimentally reproduced territory of animals (Koolhaas et al, 2013). To develop effective behavioral models that quantitatively estimate aggressive behavior in chickens, we previously monitored the aggressive behavior of male layer chicks from 8 to 24 days of age using the SI and R-I tests (Raihan et al, 2017). The chicks in the R-I test showed aggressive behavior more frequently than those in the SI test, indicating that the R-I test, rather than the SI test, is more effective in monitoring the aggressive behavior of male layer chicks.…”