Litter uniformity, which is usually represented by within-litter weight coefficient of variation at birth (CVB), could influence litter performance of sows and the profitability of pig enterprises. The objective of this study was to characterize CVB and its effect on other reproductive traits in Large White sows. Genetic parameters and genetic correlation of the reproductive traits, including CVB, within-litter weight coefficient of variation at three weeks (CVT), total number born (TNB), number born alive (NBA), number born dead (NBD), gestation length (GL), piglet mortality at birth (M₀), piglet mortality at three weeks (M₃), total litter weight at birth (TLW0), and total litter weight at three weeks (TLW₃) were estimated for 2 032 Large White litters. The effects of parity and classified litter size on CVB, CVT, TNB, NBA, NBD, GL, M₀, M₃, TLW₀, and TLW₃ were also estimated. The heritabilities of these reproductive traits ranged from 0.06 to 0.17, with the lowest heritability for CVB and the highest heritability for TLW0. Phenotypic and genetic correlations between these reproductive traits were low to highly positive and negative (ranging from −0.03 to 0.93, and −0.53 to 0.93, respectively). The genetic correlations between TNB and CVB, and between M₀ and CVB were 0.32 and 0.29, respectively. In addition, CVB was significantly influenced by parity and litter size class (P<0.05). All the results suggest that piglet uniformity should be maintained in pig production practices and pig breeding programs.

   Ear size exhibits remarkable diversity in pig breeds. LEM domain-containing 3 (LEMD3) on chromosome 5 is considered as an important candidate for porcine ear size. This is the first study on cloning and characterization of LEMD3 cDNA. The complete cDNA contains 4 843 bp, including a 2 736-bp open reading frame (ORF), a 37-bp 5´-untranslated region (UTR) and a 2 070-bp 3´-UTR. The complete LEMD3 gene is 126 241-bp and contains 13 exons and 12 introns. The ORF encodes a deduced LEMD3 protein of 911 amino acids, which shares 82–94% nucleic acid and 51–96% amino acid identity with other species. A phylogenetic tree constructed based on the amino acid sequences revealed that the porcine LEMD3 protein was closely related with cattle LEMD3. Resequencing of the ORF and promoter of LEMD3 from Minzhu pig and Large White revealed three single nucleotide polymorphisms (SNPs): L964C>A in the complete coding region, L4625A>G in the 3´ UTR, and L-394T>C in the promoter region. Genome-wide association study (GWAS) revealed that all of SNPs were shown significant association with ear size in Large White×Minzhu pig intercross population. With conditional GWAS, –log₁₀(P-value) decreased by more than 80% when each of three SNPs was included as a fixed effect. These results suggested direct involvement of LEMD3 or close linkage to the causative mutation for ear size. The findings of this study might form the basis for understanding the genetic mechanism of ear size variation in pigs and provide potential molecular markers for screening ear size diversity in pig breeds.

Although quantitative trait loci (QTLs) for number of thoracic-lumbar vertebrae have been identified on Sus scrofa chromosomes (SSCs) 1 and 7, the influence of these QTLs on the thoracic and lumbar vertebrae is not clear. The aim of this study was to identify single nucleotide polymorphisms (SNPs) associated with total number of thoracic-lumbar vertebrae and for each trait (number of thoracic and lumbar vertebrae) separately. A total of 581 individuals from an F2 Large White×Minzhu population were genotyped using an SNP60K chip. Performing a genome-wide association study (GWAS) for total number of thoracic-lumbar vertebrae, 38 significant SNPs were identified in two QTL regions located on SSC1 and SSC7. Performing a GWAS for number of thoracic vertebrae only, 72 significant SNPs were located on SSC7. While performing a GWAS for number of lumbar vertebrae only, 17 significant SNPs were identified on SSC1. Gene mining suggested that the gene encoding orphan nuclear receptor, germ cell nuclear factor (NR6A1) on SSC1 was a strong candidate affecting the number of lumbar vertebrae in pigs. Additionally, genes encoding vertnin (VRTN), prospero homeobox 2 (PROX2), Finkel-Biskis-Jinkins murine osteosarcoma viral oncogene homolog (FOS), and transforming growth factor beta 3 (TGFB3) may be important candidates affecting the number of thoracic vertebrae in pigs. QTLs on SSC1 and SSC7 independently influenced the numbers of thoracic and lumbar vertebrae. These results shed light on the complex genetic background of vertebrae development in pigs.

Spring maize is one of the most popular crops planted in northeastern China. The cropping systems involving spring maize have been maintaining high production through intensive management practices. However, the high rates of nitrogen (N) fertilizers application could have introduced a great amount of nitrous oxide (N2O) into the atmosphere. It is crucial for sustaining the maize production systems to reduce N2O emissions meanwhile maintaining the optimum yields by adopting alternative farming management practices. The goal of this study was to evaluate effects of alternative fertilization and crop residue management practices on N2O emission as well as crop yield for a typical maize field in northeastern China. Field experiments were conducted during the 2010-2011 maize growing seasons (from early May to late September) in Liaoning Province, northeastern China. N2O fluxes were measured at the field plots with six different treatments including no N fertilizer use (CK), farmers’ conventional N fertilizer application rate (FP), reduced N fertilizer rate (OPT), reduced N fertilizer rate combined with crop straw amendment (OPTS), slow-release N fertilizer (CRF), and reduced N fertilizer rate combined with nitrification inhibitor (OPT+DCD). The static chamber method combined with gas chromatography technique was employed to conduct the measurements of N2O fluxes. The field data showed that N2O emissions varied across the treatments. During the maize growing season in 2010, the total N2O emissions under the treatments of CK, FP, OPT, OPTS, and CRF were 0.63, 1.11, 1.03, 1.26, and 0.98 kg N ha-1, respectively. The seasonal cumulative N2O emissions were 0.54, 1.07, 0.96, 1.12, and 0.84 kg N ha-1, respectively, under CK, FP, OPT, OPTS, and OPT+DCD in 2011. In comparison with FP, CRF or OPT+DCD reduced the N2O emissions by 12 or 21%, respectively, while the crop yields remained unchanged. The results indicate that the reduction of N-fertilizer application rate in combination with the slow-release fertilizer type or nitrification inhibitor could effectively mitigate N2O emissions from the tested field. The incorporation of crop residue didn’t show positive effect on mitigating N2O emissions from the tested cropping system. The field study can provide useful information for the on-going debate on alternative N fertilization strategies and crop straw management in China. However, further studies would be needed to explore the long-term impacts of the alternative management practices on a wide range of environmental services.

Porcine carcass traits and organ weights have important economic roles in the swine industry. A total of 576 animals from a Large White×Minzhu intercross population were genotyped using the Illumina PorcineSNP60K Beadchip and were phenotyped for 10 traits, specifically, backfat thickness (6-7 libs), carcass length, carcass weight, foot weight, head weight, heart weight, leaf fat weight, liver weight, lung weight and slaughter body weight. The genome-wide association study (GWAS) was assessed by Genome Wide Rapid Association using the mixed model and regression-genomic control approach. A total of 31 single nucleotide polymorphisms (SNPs) (with the most significant SNP being MARC0033464, P value=6.80×10-13) were located in a 9.76-Mb (31.24-41.00 Mb) region on SSC7 and were found to be significantly associated with one or more carcass traits and organ weights. High percentage of phenotypic variance explanation was observed for each trait ranging from 31.21 to 67.42%. Linkage analysis revealed one haplotype block of 495 kb, in which the most significant SNP being MARC0033464 was contained, on SSC7 at complete linkage disequilibrium. Annotation of the pig reference genome suggested 6 genes (GRM4, HMGA1, NUDT3, RPS10, SPDEF and PACSIN1) in this candidate linkage disequilibrium (LD) interval. Functional analysis indicated that the HMGA1 gene presents the prime biological candidate for carcass traits and organ weights in pig, with potential application in breeding programs.

Agricultural production plays an important role in affecting atmospheric nitrous oxide (N2O) concentrations. Field measurements were conducted in Dalian City, Liaoning Province in Northeast China from two consecutive years (2009 and 2010) to estimate N2O emissions from a spring maize field, a main cropping system across the Chinese agricultural regions. The observed flux data in conjunction with the local climate, soil and management information were utilized to test a process-based model, DeNitrification-DeComposition (DNDC), for its applicability for the cropping system. The validated DNDC was then used for exploring strategies to reduce N2O emissions from the target field. The results showed that the major N2O pulse emissions occurred with duration of about 3-5 d after fertilizer application in both years 2009 and 2010, which on average accounted for about 60% of the total N2O emissions each year. Rainfall and fertilizer application were the major factors influencing the N2O emissions from spring maize field. The average N2O fluxes from the CK (control plot, without fertilization) and FP (traditional chemical N fertilizer) treatments were 23.1 and 60.6 μg m-2 h-1 in 2009, respectively, and 21.5 and 64.3 μg m-2 h-1 in 2010, respectively. The emission factors (EFs) of the applied N fertilizer (270 kg N ha-1) as N2ON were 0.62% in 2009 and 0.77% in 2010, respectively. The comparison of modeled daily N2O emission fluxes against observations indicated that the DNDC model had a good performance even if without adjusting the internal parameters. The modeled results showed that management practices such as no-till, changing timing or rate of fertilizer application, increasing residue incorporation, and other technically applicable measures could effectively reduce N2O emissions from the tested fields. Our study indicated that avoiding application of N fertilizers at heavy rainfall events or splitting the fertilizer into more applications would be the most feasible approaches to reduce N2O emissions from spring maize production in Northeast China.

The erythropoietin receptor (EPOR) has shown to play an important role in fetal survival by promoting the maturation of red blood cells in many studies of uterine capacity and litter size in swine. In this study, we screened the porcine EPOR gene for mutations and identified five single nucleotide polymorphisms (SNPs): g.705G>T in intron 1, g.2 373C>T in intron 4, and g.2 882C>T, g.3 035A>G, and g.3 132A>T in intron 6. We then genotyped 247 Beijing Black (BB) sows and compared the polymorphism data with the litter sizes of 1 375 parities among the sows. At first parity, there was no association of g.2 882C>T and g.3 132A>T with litter sizes. However, the CT sows in g.2 882C>T had 2.13 higher total number born (TNB) (PT had the highest litter size when compared to the two homozygotes for the later parities (PG SNP,for the later parities, the TNB of the sows with the GG genotype was 3.81 higher (PT SNP was associated with a greater litter size at both the first parity (PT SNP was significantly more common in the more prolific Chinese breeds. These results indicated that the EPOR could be an important candidate gene for litter size and g.705G>T can serve as a useful genetic marker for improving litter size in both first and later parities in swine.