Abstract
Egg production traits are economically important both for egg-laying and broiler lines of chicken. In sheep, the Q249R mutation in BMPR-IB is associated with ovulation rate. The present study cloned a partial chicken BMPR-IB fragment which contained the corresponding ovine Q249R mutation, including partial exon 6 and exon 7 and full-length intron 6. Five nucleotide changes were identified by alignment of the fragment amplified from Jining Bairi and Zang chickens. Among these nucleotide substitutions, the C/T transition at the base position of 35 and the A/G transition at the base position of 287 were found to be highly polymorphic, and named as SNPs C35T and A287G, respectively. For the SNP C35T, 331 hens of a synthetic broiler line were genotyped by a PCR-SSCP approach and allele C was found to be dominant. For the SNP A287G, 604 birds from the synthetic broiler line, a commercial egg-laying line, as well as three Chinese indigenous chicken breeds were genotyped by a PCR-RFLP technique. The associations of these two SNPs with egg production traits in the broiler line were analyzed. The results indicated that both the C35T and the A287G SNPs were not associated with egg production at 33wks and from 33wks to 42 wks (p>0.1), whereas the SNP A287G was associated with egg production from 47 to 56 wks (p<0.05). The dominance genetic effects on this latter trait and on egg production from 33 to 42 wks were significant (p<0.05).
Highlights
Egg production traits are economically important both for egg-laying and broiler lines of chickens
The Q249R mutation in Booroola Merino sheep was not detected in chickens
Some DNA markers have been found to be associated with variations in reproduction traits, such as polymorphisms in the estrogen receptor gene with litter size in pigs and Q249R mutation in the bone morphogenetic protein receptor IB (BMPR-IB) gene with ovulation rate in sheep
Summary
Egg production traits are economically important both for egg-laying and broiler lines of chickens. Chinese indigenous chicken breeds, such as Zang, Wenchang and Jining Bairi, generally have a lower egg production compared to commercial egg-laying lines. Breeding companies have tended to use Chinese indigenous chicken breeds as breeding materials to improve meat quality of commercial broiler lines. Egg production of such crossbred lines is generally much lower than commercial egg-laying or broiler lines. Approaches to increasing egg production in indigenous chicken breeds, or in such crossbred broiler lines, are essential both for breeding and for egg and meat production in chickens. A non-conservative substitution (Q249R) in the intracellular kinase domain of bone morphogenetic protein receptor IB (BMPR-IB) was found to be fully associated with the increased ovulation rate of highly prolific Booroola Merino sheep (Mulsant et al, 2001; Souza et al, 2001; Wilson et al, 2001). It is suggested that the Q249R mutation partially inactivates ovine BMPR-IB receptor activity, leading to a precocious differentiation of granulosa cells and of follicular maturation
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