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In Japan, the majority of chicken meat is obtained from fast-growing broiler chickens. Because most Japanese chicken breeds have a low meat yield and egg production, many of these breeds are endangered. Recently, the palatability of meat and eggs of native chickens has been reevaluated in the Japanese market. Jidori, which means chicken from the local, is an indigenous local chicken that is more delicious, firmer in texture, and more expensive than the broiler chickens. Most Japanese consumers recognize that the meat of Jidori chicken is richer in flavor than that of the broiler chicken. However, the reason for this rich flavor of the meat of Jidori chicken has not been elucidated. Recently, we found that arachidonic acid (AA) (C20:4n-6), a polyunsaturated fatty acid, is associated with the rich flavor of the meat and eggs of Jidori chicken. The present paper summarizes the discovery of the involvement of AA in the flavor characteristic of the meat and eggs of chicken, and also the genetic regulation of the AA content in the meat and eggs of Jidori chicken.

The objective of the present study was to evaluate the temperament of a native Japanese chicken breed (TosaJidori) using the tonic immobility test for the detection of fearfulness. Each chick (2, 5, 10 or 15-day old) was placed on its back on a table and restrained by hand. Thereafter, if the chick lay still, it was then released and observed. The number of inductions and tonic immobility duration was recorded. The duration in the male was shorter than that in the female at 2-day old, whereas higher than that in the female at 15-day old. The duration of tonic immobility was affected by age in the male (P

The Nagoya breed native to Japan is popular as a dual-purpose breed for eggs and meat. The current study describes a method to discriminate between the Nagoya breed and other breeds and commercial stocks of chicken. Four strains of the Nagoya breed established at the Aichi-ken Agricultural Research Center were analyzed using 25 microsatellite markers. In these strains, 5 of the markers (ABR0015, ABR0257, ABR0417, ABR0495, and ADL0262) had a single allele. Other chicken samples (448) of various breeds and hybrids were analyzed using the same 5 markers. None of these chicken samples had the same allele combination as the Nagoya breed strains. These 5 microsatellite markers provide a practical method to accurately discriminate the Nagoya breed from other chicken breeds.

The concentrations of progesterone, testosterone and estradiol in plasma were determined in Gifujidori hens during natural autumnal moult. The moulting period lasted 16-31 days and the hens lost 22.3-67.0g of their feathers. The plasma sex steroids decreased significantly and attained the lowest levels in the middle period of moult. The mean concentrations dur-ing moult were 86±5pg/ml in progesterone, 132±12pg/ml in testosterone and 38±3pg/ml in estradiol.

It was indicated by the genetical analysis that the short leg trait in Jitokko was controlled by a single dominant autosomal gene which was located at approximately the same locus as Cp gene reported by Landauer (1933a). The length of three leg long bones in heterozygous creeper embryos was about 4/5 of that in normal embryos. The lethal stage of homozygous creeper embryos obtained from the mating of Cp (WL-G) inter se was between 3 to 5 days of incubation. From histological and histochemical observations and counting of mitotic figures in tibiae, it was suggested that the Cp gene may precociously accerelate the differentiation of chondrocytes accompanied by the suppression of their proliferation.