Morphological and reproductive characteristics of the Ryujin-Jidori, an endangered chicken breed and their implications for breed conservation

The Ryujin-Jidori (RJ) is one of the native Japanese chicken breeds reared mainly in Tanabe-City (formerly Ryujin-Village), Wakayama Prefecture, Japan, where it has been kept by a few private breeders with a small population size and exposed to high risks of extinction. Hence, timely conservation action and intervention seemed imperative for this breed. To insure the future conservation of this breed, this study investigated morphological and reproductive characteristics of the RJ, along with its present rearing situation. The number of RJ adult birds was 68 (27 males and 41 females) around Tanabe-City in April 2012. The plumage color of both chicks and adults of the RJ was basically similar to that of the wild type. However, chicks had additional black markings on the lateral sides of the neck. In adult males, black pigmentation was conspicuous in the region along with the feather axis of the sickles and saddle hackles. Adult females had black lacing-like markings at the tips of the individual feathers, differing from the wild-type female plumage. Fertility and hatchability of the RJ were approximately 83 and 72%, respectively. When the body weight data up to 30 weeks of age were adapted to the Gompertz function, the asymptote values of males and females were 980 and 854 g, respectively. The RJ reached sexual maturity at 18-24 weeks and 26-38 weeks of age in males and females, respectively. The egg production rate during 31-35 and 41-50 weeks of age was approximately 10-25 and 10-50%, respectively. The survival rate of up to 5 and 30 weeks of age was 70 and 41%, respectively. Irrespective of the small individual number, the reproductive performance of this breed is relatively high. Thus, it is important for the RJ to be propagated immediately by taking advantage of its reproductive performance.