Growth and reproduction are 2 economically important traits in the poultry industry. Janus kinase 2 (JAK) participates in the JAK2/signal transducer and activator of transcription 5 growth hormone signaling pathway, which plays important roles in the processes of growth and reproduction. The present study was designed to investigate the association of JAK2 SNP and haplotypes with growth as well as with reproductive traits in chickens. Fourteen JAK2 SNP were identified by pooled DNA sequencing, and 5 of these were genotyped for 768 Beijing You hens by using a matrix-assisted laser desorption/ionization-time of flight mass spectrometry assay. For 5 growth traits, BW at 17 wk of age was significantly associated with JAK2 C28109928T and A28135099G (P < 0.05). The 2 SNP were strongly related to BW at first egg, egg weight at first egg, and egg weight at 36 wk of age (P < 0.05). The SNP JAK2 C28122751T was found to be associated with BW at first egg and egg weight at 36 wk of age (P = 0.041 and P = 0.046, respectively), whereas JAK2 G28132240C was related to egg number at 40 wk of age (P < 0.01). Further haplotype analyses showed that 4 haplotypes checked in the population had no distinct influence on growth traits but were associated with 7 reproductive traits, namely, age at first egg; BW at first egg; egg weight at first egg; egg weight at 36 wk of age; and egg numbers at 32, 36, and 40 wk of age (P < 0.05). The results indicated that the JAK2 polymorphisms could be potential molecular markers to improve laying performance and growth traits in chickens.

Using data on age at 100 kg of three pig breeds (Large White, Landrace and Duroc) the connectedness between herds in China was evaluated by the connectedness rating (CR) method. The results show that most herds in China have low average CR (0-3.59%) with other herds. In Large White, of the 36 herds analyzed there are 20 herds, which are connected with at least one other herd. In Landrace and Duroc, of the 27 and 18 herds analyzed, only four and five herds, respectively, were found having connectedness with other herds. Generally, the connectedness exists only among two or few herds in the same region. A certain degree of connectedness between herds is a precondition for cross-herd genetic evaluation. A national or regional cross-herd genetic evaluation is not practicable at the present time in China. More intense efforts are needed to establish and enhance the connectedness between herds by means of extensively using artificial insemination (AI) in the swine industry in China.

Bovine placental lactogen (bPL) is structurally related to prolactin (PRL) and growth hormone (GH). In synergism with steroid and thyroid hormones, bPL is crucial in stimulating the development of the mammary gland, mammary cell differentiation and function. To further explore whether bPL gene is associated with milk production traits, we herein analyzed single-nucleotide polymorphisms (SNPs) within eight regions of bPL gene, which are potentially associated with five milk production traits on 1028 Chinese Holstein cows. Among these, two SNPs, NT7409(T-C) and Nt11246(G-A), were identified. The former is within exon 2; it induces an alteration of amino acid from Val to Ala. The later is within exon 4. It is a synonymous mutation. We found that there were significant associations between NT7409(T-C) and milk and protein yield. Cows of the AA genotype yielded less milk ( P 5 0.001) and less protein ( P 5 0.003) than those of genotypes AB and BB. However, on the NT11246(G-A) locus, no significant association was observed in the five milk production traits studied. In addition, bPL has been localized near markers RM185 and CC549051 with a distance of 23.2 cR on BTA 23. It is at the same position as the region including quantitative trait loci (QTLs) affecting milk and protein yields by previous linkage analysis. In summary, our findings demonstrated that the SNP within exon 2 of bPL (NT7409(T-C)) is associated with two milk production traits, and this provided further evidence that bPL could be a major gene-controlling milk production trait in Holstein dairy cattle.