Effect of a Single Nucleotide Polymorphism in the Cholecystokinin Type A Receptor Gene on Growth Traits of the Miyazaki Jitokko Chicken

The Miyazaki Jitokko chicken, native to the Miyazaki Prefecture in southern Kyushu Island, Japan, is the product of a three-way cross involving the Jitokko, White Plymouth Rock, and Kyushu Rhode breeds. In the present study, associations between a single nucleotide polymorphism (SNP; AB604331, g.420 C>A) of the chicken cholecystokinin type A receptor gene and growth traits in Miyazaki Jitokko chickens were investigated. Unrelated male birds (n=120) that had hatched on the same day were raised in the same chicken house and fed the same diet ad libitum from day 0 to 17 weeks of age. Body weight was recorded at 0, 1, 2, 3, 4, 5, 7, 9, 11, 13, 15, and 17 weeks and the average daily gain of each interval was calculated from the body weight data. SNP genotyping of each bird was performed using the mismatch amplification mutation assay. The associations between the SNP and growth traits were examined using the Thesias program. The genotype frequencies of AA, AC, and CC were 0.525, 0.383, and 0.092, respectively. AA birds were significantly heavier than CC birds from 4 to 17 weeks of age. In the estimated effect of alleles, body weight from 1 to 17 weeks of age in birds with the A allele was greater than that in birds with the C allele. During the rearing period, the effect of the A allele on average daily gain in the first half was greater than that in the second half. We conclude that the g.420 C>A SNP can be used as a selection marker for the parent stock lines of the Miyazaki Jitokko chickens to increase their growth performance.