The objectives of the research were to determine the association of Dopamine Receptor D2 type (DRD2) and Vasoactive Intestinal Peptide (VIP) on egg production in 281 high egg strain of Pradu Hangdum Chiangmai chickens (HPHC). PCR-RFLP protocols were used to identify polymorphisms of both genes. The frequencies of TT, TC and CC genotypes of DRD2 were 0.05, 0.40, and 0.55, respectively. The frequencies of T and C alleles of DRD2 were 0.25 and 0.75, respectively. Regarding VIP, the frequencies of II, ID and DD genotypes were 0.59, 0.28, and 0.13, respectively. The frequencies of I and D alleles of VIP were 0.73 and 0.27, respectively. The association of DRD2 polymorphism were detected on egg number at 360 days (EN360) and egg per month (EM) (P<0.05). The chickens carrying the CC genotype had higher EN360 and EM (189.82 eggs and 15.81 eggs) and the ones carrying the TC (180.98 eggs and 15.08 eggs) and the TT genotype (176.38 eggs and 14.69 eggs) was non-significant. The VIP polymorphism were associated on egg number at 270 days (EN270), EN360 and EM (P<0.01). The DD genotype had higher EN270, EN360 and EM when compared to the ID and II genotypes. The DRD2 and VIP genes were moderate polymorphism and their alleles could be the potential genetic markers for chickens' selection to improve egg number.
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