Tonic Immobility and Open Field Responses in Nagoya, White Leghorn, and White Plymouth Rock Chicks

Abstract

Innate fear responses to tonic immobility (TI) and open field (OF) were evaluated in newly hatched chicks of three breeds with distinct breed origin and genetic relationships. The breeds studied were Nagoya (NAG), a native Japanese breed; White Leghorn (WL), a representative of layers; and White Plymouth Rock (WPR), a parental breed of common broilers. The TI test revealed that WL was the most sensitive to extensive fear evoked by the TI test among the three breeds, followed in order by WPR, and NAG. In contrast, the OF test revealed that NAG was the most sensitive to mild fear evoked by the OF test, followed in order by WPR, and WL. The different fear responses between NAG and WL were supported by minimal phenotypic correlations between TI and OF traits in each breed. These results demonstrated that NAG and WL breeds exhibit extreme and opposite responses to TI and OF fears.

Genetic Architecture of Innate Fear Behavior in Chickens

“…To understand the genetic architecture of innate fear behavior, we aimed in this study to identify QTL for innate responses to TI and OF fears in an F 2 intercross population of newly hatched chicks between NAG and WL breeds by construction of a dense genetic linkage map based on single nucleotide polymorphism (SNP) markers obtained by restriction site-associated DNA sequencing (RAD-seq). The two breeds were previously found to exhibit opposite responses to TI and OF fears, as described above (Sakaguchi and Ishikawa 2020). To the best of our knowledge, the present study is the first QTL analysis for innate fear behavioral traits in newly hatched chicks before establishment of social hierarchy.…”

“…The same NAG and WL breeds as those used in our previous study (Sakaguchi and Ishikawa 2020) were used in this study as grandparental breeds to develop an F 2 mapping population for QTL analysis. Five females of WL were crossed with a male of NAG, producing 42 F 1 birds.…”

“…Seven females and six males of the F 1 birds obtained were crossed inter se, producing 266 F 2 birds. Incubation of the F 1 and F 2 hatching eggs and the husbandry of all hatched chicks were performed as previously described (Sakaguchi and Ishikawa 2020).…”

“…TI and OF tests were performed by the same experimenter on newly hatched chicks in a quiet room at a temperature of approximately 30 °C, as described by Sakaguchi and Ishikawa (2020). Briefly, on the hatching day, the TI test was performed using a V-shaped cradle covered with black felt.…”

“…Abe et al (2013) reported differences in an innate response to fear evoked by a tonic immobility (TI) test between two breed chicks at 1-2 days of age in WL and Nagoya (NAG), a native Japanese breed with high-quality production of meat and eggs. Using chicks at 0-1 days of age in three genetically distinct breeds of NAG, WL and White Plymouth Rock (WPR), a parental breed of common broilers, we recently revealed opposite responses to strong and mild fears induced by TI and OF tests, respectively (Sakaguchi and Ishikawa 2020). That is, WL is the most sensitive to strong TI fear among the three breeds, followed in order by WPR and NAG, whereas NAG is the most sensitive to mild OF fear, followed in order by WPR and WL.…”