The leptin receptor (LEPR) gene is a member of the class I cytokine receptor family, which plays an important role in weight regulation, fat accumulation and neuroendocrine function in animals. This study aimed to explore the association of single nucleotide polymorphisms (SNPs) of the LEPR gene with growth and carcass traits in meat-type quail by PCR amplification and DNA direct sequencing. In this study, genomic DNA was extracted from blood samples of 36 female Savimalt (SV) quails and 49 female French Giant (FG) quails. Growth traits (measured at 3 or 5 wk) and carcass traits (measured at 5 wk) were used for LEPR gene association analysis. The results showed the existence of 9 SNPs (T81C, G90T, C187A, A191G, A219G, G258A, C286T, G346A, and G373A) of the LEPR gene in the 2 quail strains. The statistical analyses indicated that these SNPs of LEPR gene was significantly associated with shank circumference (SC), shank length (SL), breastbone length (BBL), heart rate (HR), and whole net carcass rate (WNCR) of FG (P < 0.05); chest width (CW), body length (BL), leg muscle rate (LMR), whole net carcass rate (WNCR), and heart rate (HR) of SV (P < 0.05). While haplotypes showed significant effect on SL, BBL, heart weight (HW), WNCR, and HR of FG (P < 0.05). Therefore, the LEPR gene may serve as a molecular genetic marker for improving growth and carcass traits in quails.

Insulin-like growth factor 1 receptor (IGF-1R) gene is the main effector of insulin-like growth factor (IGF), which plays an important role in growth, development and reproduction of the animal organism. This study aimed to investigate the association of IGF-1R gene single nucleotide polymorphisms (SNPs) with egg quality and carcass traits of quail by direct sequencing. In this study, genomic DNA was extracted from quail blood samples of 46 Chinese yellow (CY) quail, 49 Beijing white (BW) quail and 48 Korean (KO) quail strains. Egg quality and carcass traits were measured and used for IGF-1R gene analysis in 3 quail strains. The results showed that 2 SNPs (A57G and A72T) of the IGF-1R gene were detected in 3 quail strains. The A57G was significantly associated with yolk width (YWI) in BW strain (P < 0.05). Whereas A72T was significantly associated with egg shell thickness (EST) in BW strain (P < 0.05), and significantly associated with egg weight (EW), egg long (EL), and egg short (ES) in KO strain (P < 0.05). Haplotypes based on 2 SNPs showed significant effect on EST in 3 quail strains (P < 0.05), it also has a significant effect on EW in KO strain (P < 0.05). Meanwhile, A72T was significantly associated with liver weight (LW) and dressing percentage (DP) in 3 strains (P < 0.05). Haplotypes showed significant effect on LW (P < 0.05). Therefore, the IGF-1R gene may be a molecular genetic marker to improve egg quality and carcass traits in quails.

This study investigated SNP mutation sites of Gonadotrophin releasing hormone (GnRH) gene in China yellow quail, Beijing white quail and Korean quail through PCR amplification and DNA sequencing technologies. Moreover, polymorphism of GnRH gene and its association with growth traits of quail were analyzed, aiming to get molecular markers associated to growth traits of quail, which could provide references for breeding of new quail species. According to research results, a total of 14 SNP mutation sites of GnRH were detected in China yellow quail, Beijing white quail and Korean quail, which were C71T, C108T, C168T, C178T, A184G, C206T, A209C, C215T, A252G, A279T, C281T, C293G, C339T and C458T. Except that only 2 genotypes were detected for A209C and C281T in China yellow quail and Beijing white quail, 3 genotypes were detected for all of the remaining 12 SNP mutation sites in three quail species. Of the 14 SNP sites, C71T, A209C, C215T, C281T, C293G, C339T and C458T were significantly associated with body weight (p<0.05), C71T, C108T, C168T, C178T, A184G, C206T, C215T, A252G, C293G, C339T and C458T were significantly associated with shank length (p<0.05), C71T, C215T, C293G and C458T were significantly associated with breastbone length (p<0.05), A209C and C281T were significantly associated with shank circumference (p<0.05).

This study aimed to analyze the polymorphism of the vasoactive intestinal peptide receptor-1 (VIPR-1) gene and its association with growth traits in quail using the PCR-RFLP and sequencing techniques. Genomic DNA was extracted from blood samples of 36 female Savimalt (SV) quails and 49 female French Giant (FG) quails. Growth traits were measured and used for VIPR-1 gene analysis, as body weight (BW), tibia length (TL), chest width (CW), chest depth (CD), sternum length (SL), body length (BL), and tibia circumference (TC). The results showed that 2 SNPs (BsrD I and HpyCH4 IV) were detected in exon 4 to 5 and exon 6 to 7 of the VIPR-1 gene, respectively. The results of association showed that the BsrD I site was not significantly associated with growth traits at 3 or 5 wk of age in the SV strain (P < 0.05), while the BsrD I site was significantly associated with BL at 3 or 5 wk of age in FG (P < 0.05). The HpyCH4 IV site was significantly associated with TL, CW, CD, SL, and BL at 3 wk of age in the SV strain (P < 0.05), while the HpyCH4 IV site was significantly correlated with BW, CW, SL, and BL at 5 wk of age in SV (P < 0.05). The HpyCH4 IV site was significantly associated with TL and TC at 3 wk of age in FG (P < 0.05), while the HpyCH4 IV site was significantly associated with TC at 5 wk of age in FG (P < 0.05). Four haplotype combinations based on 2 SNPs showed significantly association with BW, CW, CD, SL, BL, and TC at 3 or 5 wk of age in SV (P < 0.05). There was not significant association between 3 haplotype combinations with growth trait at 3 or 5 wk of age in FG (P > 0.05). In conclusion, the VIPR-1 gene could be used as a molecular genetic marker to improve growth traits in quail.

In this study, POU1F1 gene polymorphism was detected in five sheep populations (large-tailed Han, small-tailed Han, Yuxi fat-tailed, Lanzhou large-tailed, and Mongolian sheep), using DNA pooling and sequencing, to provide theoretical basis for the breeding of excellent sheep varieties. Three single-nucleotide polymorphism (SNP) loci of POU1F1 gene were detected in five sheep populations, namely C355T (C/T), C71G (C/G), and C330G (C/G). C and T frequencies of C355T were 0.67/0.33, 0.81/0.19, 0.67/0.33, 1.00/0.00, and 0.93/0.07, respectively, in large-tailed Han, small-tailed Han, Yuxi fat-tailed, Mongolian, and Lanzhou large-tailed sheep. C of C355T locus was the dominant allele in five sheep populations. C and G allele frequencies of C330G locus were detected in Yuxi fat-tailed sheep; their frequencies were 0.75 and 0.25, respectively. C and G allele of C71G locus were only detected in Yuxi fat-tailed and large-tailed Han sheep; their frequencies were 0.87/0.13 and 0.87/0.13, respectively. The cluster analysis based on POU1F1 gene sequence showed that bactrian camel, dromedary, and wild camel clustered first, and dolphin and killer whales clustered according to taxonomy. Although the four species Tibetan antelope, buffalo, goat, and sheep were alone, they got close and the relative genetic relationship was intimate according to the dendrogram. The mutation site analysis of the POU1F1 gene in five sheep populations in this study would be favorable for uncovering the function of POU1F1 gene deeply.

This study aimed to identify polymor-phisms of gonadotropin-releasing hormone (GnRH) gene and their association with growth traits in quail by PCR and direct sequencing. Genomic DNA was extracted from quail blood samples of 36 from Savimalt (SV) and 49 from French Giant (FG). Growth traits were measured and used for candidate gene analysis, as body weight (BW), shank length (SL), chest width (CW), chest depth (CD), breastbone length (BBL), body length (BL), and shank circumference (SC). The results showed that a total of 20 SNPs were detected in GnRH gene, whereas 8 SNPs were significantly associ-ated with growth traits (P < 0.05). The T215C, G279A, C458T, A520G, and C547G were significantly associated with SL at 3 wk of age in the FG strain, whereas A583T was significantly related to BBL and BL, and C591T was significantly related to SL, BBL, and BL, whereas A592G was significantly correlated with SL, CW, CD, BBL, and BL (P < 0.05). The 8 SNPs were significantly related to CW, CD, and BBL at 3 wk of age in the SV strain, whereas A583T, C591T, and A592G were signifi-cantly associated with BW (P < 0.05). The G279A showed significant correlations with SL at 5 wk of age in FG, whereas A583T showed significant associations with SC in FG, and C591T was significantly associated with BW and SC in FG, whereas A592T was signifi-cantly related to BW, SL, and CD in FG (P < 0.05). The T215C, G279A, C458T, A520G, and C547G were significantly correlated with BW, CW, BBL, and BL at 5 wk of age in SV, whereas A583T, C591T, and A592G were significantly related to BW, SL, CW, BBL, and BL (P < 0.05). Haplotypes based on 8 SNPs showed signifi-cant correlation with BW, SL, CW, CD, BBL, BL, and SC in FG (P < 0.05). In conclusion, the GnRH gene could be used as a molecular genetic marker to provide theoretical foundation to improve growth traits in quail.