Verification of the Effectiveness of an SNP Marker in the Cholecystokinin Type A Receptor Gene for Improving Growth Traits in Okumino-kojidori Chickens

Abstract

sA significant association was reported between a single nucleotide polymorphism (SNP; AB604331, g. 420 C > A) in the cholecystokinin type A receptor gene and growth traits in some Japanese slow-growing chickens. Demonstration tests of the genetic improvement effect by comparing the superior allele-A fixed chickens with conventional ones were carried out considering the effect of different seasons on growth traits in other slow-growing chickens. Meat-type Okumino-kojidori chickens from Gifu Prefecture are a three-way cross of Gifu-jidori improved, White Plymouth Rock, and Rhode Island Red breeds. We used a total of 468 meat-type Okumino-kojidori: 264 individuals from a private hatchery as conventional chickens and 204 A-allele fixed individuals from the Gifu Prefectural Livestock Research Institute as improved chickens. We performed fattening experiments over two seasons: summer and winter. In each season, experimental birds of both sexes were hatched on the same day, raised in the same chicken house, and fed the same diet ad libitum for 12 weeks. Body weight was recorded at 3, 6, 9, and 12 weeks of age. SNP genotypes were determined using the mismatch amplification mutation assay. Association between the SNP and growth traits was analyzed using generalized linear models built on sex-based, seasonal, additive, and dominance genetic effects. The observed AA, AC, and CC genotype frequencies in the conventional chickens were 0.158, 0.479, and 0.363, respectively; body weight at 12 weeks and average daily gain from 3 to 12 weeks was superior for the A allele compared to the C allele. The improved chickens were heavier than the conventional ones at 12 weeks. Body weight at 12 weeks in allele-A fixed chickens increased by 3.2% compared to the conventional chickens. We concluded that g. 420 C > A is a good selective marker that increases slaughter weight in the meat-type Okumino-kojidori chickens.

Practical Application of Miyazaki Jitokko Chickens Selected for a Superior Allele at a Single Nucleotide Polymorphism Site in the Cholecystokinin Type A Receptor Gene

“…For example, in the distal region of chromosome 4 where CCKAR is located, the CCKAR SNPs— other than g.420 C>A ( Dunn et al , 2013 ) and the SNPs in other candidate genes ( Lyu et al , 2017 )—have been suggested to affect growth traits by studies on resource populations of White Leghorn×commercial broilers ( Dunn et al , 2013 ) and New Hampshire×White Leghorn ( Lyu et al , 2017 ), respectively. Regardless, without doubt, the g.420 C>A SNP is a quality marker for marker-assisted selection to improve growth traits with a wide application range in chickens, since a significant association is reported between the SNP and growth traits in other commercial slow-growing chickens (Amakusa Daioh cross chicken, Takahashi et al , 2019 ; Miyazaki Jitokko chicken, Horinouchi et al , 2019 ; Hinai-jidori chicken, Rikimaru et al , 2019 ; Okuminokojidori chicken, Ishikawa et al , 2020 ).…”

“…The National Agriculture and Food Research Organization (NARO) and the Akita Prefectural Livestock Experiment Station have reported that a SNP site (AB604331, g.420 C>A in DDBJ; rs313822901 in NCBI dbSNP) in the 5 ′ -untranslated region of the cholecystokinin type A receptor gene ( CCKAR ) is associated with growth traits in the Hinai-dori breed of the Akita Prefecture in Honshu, Japan (Rikimaru et al , 2013). The effectiveness of the g.420 C>A SNP as a selection marker for improved growth traits has been investigated in other commercial slow-growing chickens (Amakusa Daioh cross chicken, Takahashi et al , 2019 ; Miyazaki Jitokko chicken, Horinouchi et al , 2019 ; Hinaijidori chicken, Rikimaru et al , 2019 ; Okumino-kojidori chicken, Ishikawa et al , 2020 ). These studies conclude that the A allele of the g.420 C>A SNP is superior for improving growth traits.…”