A genome-wide association analysis for susceptibility of pigs to enterotoxigenic Escherichia coli F41

Enterotoxigenic Escherichia coli (ETEC) is a type of pathogenic bacteria that cause diarrhea in piglets through colonizing pig small intestine epithelial cells by their surface fimbriae. Different fimbriae type of ETEC including F4, F18, K99 and F41 have been isolated from diarrheal pigs. In this study, we performed a genome-wide association study to map the loci associated with the susceptibility of pigs to ETEC F41 using 39454 single nucleotide polymorphisms (SNPs) in 667 F₂ pigs from a White Duroc×Erhualian F₂ cross. The most significant SNP (ALGA0022658, P=5.59×10⁻¹³) located at 6.95 Mb on chromosome 4. ALGA0022658 was in high linkage disequilibrium (r²>0.5) with surrounding SNPs that span a 1.21 Mb interval. Within this 1.21 Mb region, we investigated ZFAT as a positional candidate gene. We re-sequenced cDNA of ZFAT in four pigs with different susceptibility phenotypes, and identified seven coding variants. We genotyped these seven variants in 287 unrelated pigs from 15 diverse breeds that were measured with ETEC F41 susceptibility phenotype. Five variants showed nominal significant association (P<0.05) with ETEC F41 susceptibility phenotype in International commercial pigs. This study provided refined region associated with susceptibility of pigs to ETEC F41 than that reported previously. Further works are needed to uncover the underlying causal mutation(s).     

Leaf meristems: an easily ignored component of the response to human disturbance in alpine grasslands

Grazing and fencing are two important factors that influence productivity and biomass allocation in alpine grasslands. The relationship between root (R) and shoot (S) biomass and the root:shoot ratio (R/S) are critical parameters for estimating the terrestrial carbon stocks and biomass allocation mechanism responses to human activities. Previous studies have often used the belowground:aboveground biomass ratio (M_b/M_a) to replace the R/S in alpine ecosystems. However, these studies may have neglected the leaf meristem biomass, which belongs to the shoot but occurs below the soil surface, leading to a significant overestimation of the R/S ratio. We conducted a comparative study to explore the differences between the R/S and M_b/M_a at both the species (Stipa purpurea, Carex moorcroftii, and Artemisia nanschanica) and community levels on a Tibetan alpine grassland with grazing and fencing management blocks. The results revealed that the use of the M_b/M_a to express the R/S appeared to overestimate the actual value of the R/S, both at species and community levels. For S. purpurea, the M_b/M_a was three times higher than the R/S. The M_b/M_a was approximately two times higher than the R/S for the species of C. moorcroftii and A. nanschanica and at the community level. The relationships between the R‐S and M_b‐M_a exhibited different slopes for the alpine plants across all the management practices. Compared to the fenced grasslands, the plants in the grazing blocks not only allocated more biomass to the roots but also to the leaf meristems. The present study highlights the contribution of leaf meristems to the accurate assessment of shoot and belowground biomasses. The R/S and M_b/M_a should be cautiously used in combination in the future research. The understanding of the distinction between the R‐S and M_b‐M_a may help to improve the biomass allocation mechanism response to human disturbances in an alpine area.     

Heterotopic Renal Autotransplantation in a Porcine Model: A Step-by-Step Protocol

Kidney transplantation is the treatment of choice for patients suffering from end-stage renal disease. It offers better life expectancy and higher quality of life when compared to dialysis. Although the last few decades have seen major improvements in patient outcomes following kidney transplantation, the increasing shortage of available organs represents a severe problem worldwide. To expand the donor pool, marginal kidney grafts recovered from extended criteria donors (ECD) or donated after circulatory death (DCD) are now accepted for transplantation. To further improve the postoperative outcome of these marginal grafts, research must focus on new therapeutic approaches such as alternative preservation techniques, immunomodulation, gene transfer, and stem cell administration.Experimental studies in animal models are the final step before newly developed techniques can be translated into clinical practice. Porcine kidney transplantation is an excellent model of human transplantation and allows investigation of novel approaches. The major advantage of the porcine model is its anatomical and physiological similarity to the human body, which facilitates the rapid translation of new findings to clinical trials. This article offers a surgical step-by-step protocol for an autotransplantation model and highlights key factors to ensure experimental success. Adequate pre- and postoperative housing, attentive anesthesia, and consistent surgical techniques result in favorable postoperative outcomes. Resection of the contralateral native kidney provides the opportunity to assess post-transplant graft function. The placement of venous and urinary catheters and the use of metabolic cages allow further detailed evaluation. For long-term follow-up studies and investigation of alternative graft preservation techniques, autotransplantation models are superior to allotransplantation models, as they avoid the confounding bias posed by rejection and immunosuppressive medication.     

Inhibition of the Arp2/3 complex impairs early embryo development of porcine parthenotes

The Arp2/3 complex, which nucleates actin filaments, comprises a stable assembly of seven-protein subunits including two actin-related proteins (Arp2 and Arp3). Previous work showed that Arp2/3 binds to the sides of actin filaments and is concentrated at the leading edges of motile cells. In the present study, we show that the Arp2/3 complex is critical for cytokinesis during early embryonic development in porcine parthenotes. The Arp2/3 complex is concentrated at the cortex of each cell at the 1-, 2-, and 4-cell stages, and at the periphery at the morula stage. The amount of Arp2/3 significantly decreased at the blastocyst stage in parthenogenetically activated porcine embryos. Inhibition of the Arp2/3 complex in the pig embryos by the Arp2/3-specific inhibitor CK666 resulted in abnormal cell division, a decrease in developmental rate and total cell numbers, and an increase in the ratio of trophectoderm cell number to inner cell mass number in blastocyst-stage embryos. In addition, 4-cell stage embryos subjected to CK666 treatment exhibited significantly decreased expression of ZGA genes (Pou5f1, Sox2, and Nanog), suggesting that the Arp2/3 complex plays an important role in early porcine embryo development. Thus, our data demonstrate that the Arp2/3 complex is required for early embryonic development in pigs and appears to regulate the expression of pluripotency genes.     

A modified framework for the regional assessment of climate and human impacts on net primary productivity

Improving models that depict the components of net primary production (NPP) in ecosystems will help us to better understand how climate change and human activities affect the biosphere. In this study, NPP_gap was introduced into the present human appropriation of net primary production (HANPP) framework. We introduced NPP_gap in this study as potential NPP (NPP_pot) minus the sum of ecosystem NPP (NPP_eco) and HANPP, which relates to the ability of models to depict NPP components. Using the Lhasa River region of the Tibetan Plateau, we examined temporal and spatial variations in the components of NPP over a 10-year period. Results showed that NPP_pot, HANPP and NPP_eco increased from 2000 to 2010, but at different rates and with different spatial patterns. NPP_gap each year ranged from −9.2% to 13.1% for each site and on average composed 1.2% of the total NPP_pot. NPP_gap was significantly correlated with precipitation, plant biodiversity, plant height and soil properties. NPP_gap increased if either of the previous 2 years had been wet years with relative high precipitation. An increase in the richness of palatable species would lead to a larger NPP_gap through more compensatory growth. The large fluctuation level of NPP_gap reflected the higher stability of vegetation productivity, which is caused by higher plant heights and soil maximum water capacity. This study showed the potential of the HANPP framework in regional assessment of climate and human impacts on net primary productivity. The use of the NPP_gap measure reflects the gap in our knowledge and our ability to accurately estimate the components of NPP.     

Comparison of boosted regression tree and random forest models for mapping topsoil organic carbon concentration in an alpine ecosystem

Soil organic carbon (SOC) plays an important role in soil fertility and carbon sequestration, and a better understanding of the spatial patterns of SOC is essential for soil resource management. In this study, we used boosted regression tree (BRT) and random forest (RF) models to map the distribution of topsoil organic carbon content at the northeastern edge of the Tibetan Plateau in China. A set of 105 soil samples and 12 environmental variables (including topography, climate and vegetation) were analyzed. The performance of the models was evaluated using a 10-fold cross-validation procedure. Maps of the mean values and standard deviations of SOC were generated to illustrate model variability and uncertainty. The results indicate that the BRT and RF models exhibited very similar performance and yielded similar predicted distributions of SOC. The two models explained approximately 70% of the total SOC variability. The BRT and RF models robustly predicted the SOC at low observed SOC values, whereas they underestimated high observed SOC values. This underestimation may have been caused by biased distributions of soil samples in the SOC space. Vegetation-related variables were assigned the highest importance in both models, followed by climate and topography. Both models produced spatial distribution maps of SOC that were closely related to vegetation cover. The SOC content predicted by the BRT model was clearly higher than that of the RF model in areas with greater vegetation cover because the contributions of vegetation-related variables in the two models (65% and 43%, respectively) differed significantly. The predicted SOC content increased from the northwestern to the southeastern part of the study area, average values produced by the BRT and RF models were 27.3 g kg⁻¹ and 26.6 g kg⁻¹, respectively. We conclude that the BRT and RF methods should be calibrated and compared to obtain the best prediction of SOC spatial distribution in similar regions. In addition, vegetation variables, including those obtained from remote sensing imagery, should be taken as the main environmental indicators and explicitly included when generating SOC maps in Alpine environments.     

A molecularly imprinted polymer based chemiluminescence array sensor for one‐step determination of phenothiazines and benzodiazepines in pig urine

The residues of phenothiazines and benzodiazepines in foods of animal origin are dangerous to consumers. For inspection of their abuses, this study for the first time reported on the use of a chemiluminescence array sensor for the simultaneous determination of four phenothiazines and five benzodiazepines in pig urine. Two molecularly imprinted polymers were coated in different wells of a conventional 96‐well microtiter plate as the recognition reagents. After sample loading, the absorbed analytes were initiated directly by using an imidazole enhanced bis(2,4,6‐trichlorophenyl)oxalate–hydrogen peroxide system to emit light. The assay process consisted of only one sample‐loading step prior to data acquisition, so one test was finished within 10 min. The limits of detection for the nine drugs in the pig urine were in a range of 0.1 to 0.6 pg/mL, and the recoveries from the fortified blank urine samples were in a range of 80.3 to 95%. Furthermore, the sensor could be reused six times. Therefore, this sensor could be used as a simple, rapid, sensitive and reusable tool for routine screening for residues of phenothiazines and benzodiazepines in pig urine.     

Factors affecting piglet mortality during the first 24 h after the onset of parturition in large litters: effects of farrowing housing on behaviour of postpartum sows

The present study aimed to identify the factors that affect immediate (within 24 h after farrowing onset) postnatal piglet mortality in litters with hyperprolific sows, and investigate their associations with behaviour of postpartum sows in two different farrowing housing systems. A total of 30 sows were housed in: (1) CRATE (n=15): the farrowing crate closed (0.80×2.20 m) within a pen (2.50×1.70 m), and (2) OPEN (n=15): the farrowing crate open (0.80×2.20×1.80 m) within a pen (2.50×2.40 m) with a provision of 20 ls of hay in a rack. A total of 518 live born piglets, produced from the 30 sows, were used for data analyses during the first 24 h after the onset of parturition (T24). Behavioural observations of the sows were assessed via video analyses during T24. Total and crushed piglet mortality rates were higher in OPEN compared with CRATE (P<0.01, for both). During T24, the OPEN sows tended to show higher frequency of postural changes (P=0.07) and duration of standing (P=0.10), and showed higher frequencies of bar-biting (P<0.05) and piglet trapping (P<0.01), when compared with the CRATE sows. During T24, the mortality rates caused by crushing were correlated with the piglet trapping event (r=0.93, P<0.0001), postural changes (r=0.37, P<0.01), duration of standing (r=0.32, P<0.01) and frequency of bar-biting behaviour (r=0.51, P<0.01) of the sows (n=30). In conclusion, immediate postnatal piglet mortality, mainly due to crushing, may be associated with potential increases in frequency of postural changes, duration of standing and incidence of piglet trapping in postpartum sows in the open crate system with large litters.     

Economic weights of maternal and direct traits of pigs calculated by applying gene flow methods

Multiple trait selection indexes in pig breeding programmes should take into account the population structure and time delay between parent selection and expressions of traits in all production levels next to the trait impacts on economic efficiency of production systems. Gene flow procedures could be used for the correct evaluation of maternal and direct traits of pig breeds involved in breeding or crossbreeding systems. Therefore, the aim of this study was to expand a previously developed bioeconomic model and computer program to calculate the marginal economic values by including a gene flow procedure to calculate the economic weights for maternal and direct traits in pig breeds. The new program was then applied to the three-way crossbreeding system of the Czech National Programme for Pig Breeding. Using this program, the marginal economic values of traits for dam breeds Czech Large White in the dam position and Czech Landrace in the sire position, and for the sire breed Pietrain were weighted by the number of discounted gene expressions of selected parents of each breed summarised within all links of the crossbreeding system during the 8-year investment period. Economic weights calculated in this way were compared with the approximate economic weights calculated previously without a gene flow procedure. Taking into account the time delay between parent selection and trait expression (using discounting with half-year discount rates of 2% or 5%) and including more than one generation of parent progeny had little impact on the relative economic importance of maternal and direct traits of breeds involved in the evaluated three-way crossbreeding system. These results indicated that this gene-flow method could be foregone when estimating the relative economic weights of traits in pig crossbreeding systems applying artificial insemination at all production levels.