Associations between polymorphisms in the chicken VIP gene, egg production and broody traits.

1. In this study, the vasoactive intestinal peptide (VIP) gene was screened for variations by cloning and sequencing to analyse the association with chicken egg production and broodiness traits. 2. Sequencing revealed that 69 polymorphisms were found in a 9305-bp length of the chicken VIP gene, of which 39 were located in introns, 28 in 5' regulatory region, 1 in exon 6 (synonymous) and 1 in 3'-UTR. The nucleotide diversity corrected for sample size was 1.96 x 10(-3). 3. Five polymorphisms, C-3134T, "AGG" indel at -2648 to -2650, C + 338T, G + 780T and A + 4691G, were genotyped in 644 individuals of Ningdu Sanhuang chickens to evaluate their effects on egg production and broodiness traits. Marker-trait association analyses showed that the "AGG" indel was associated with total number of eggs from 90 to 300 d of age and total number of qualified eggs from 90 to 300 d of age. In contrast, C + 338T was associated with duration of broodiness.