农林科学最新文献

Runs of Homozygosity (ROH) are commonly used to quantify autozygosity/identity-by-descent (IBD) in an individual or population. However, the method's accuracy at the segment level in livestock populations has only been evaluated in a few studies. Thus, the aim of this study was to determine to what extent ROH are truly IBD and estimate the proportion of IBD segments that go undetected in a simulated livestock population. We simulated a population of randomly mating animals for 100 generations. The genome consisted of a single chromosome with a SNP density of either 46 or 92 SNPs per mega base (Mb). In addition, a set of founder markers tracing IBD was recorded. ROH were detected using four different parameter combinations. Using the two sets of markers, we calculated the true positive rate, power, and overall correlation between true (F_IBD) and estimated inbreeding (F_ROH). Additionally, a new measure for within-ROH inbreeding (F|ROH) was introduced and calculated the level of homozygosity within a ROH compared to the general expectation in the genome. The results indicate that ROH longer than 2 Mb are a reliable indicator of IBD, with the F|ROH being over 0.9 for all ROH lengths and parameter combinations. True positive rates only exceeded 0.9 consistently for ROH over 9 Mb, indicating that many of the identified ROH may be associated with common ancestors more ancient than the base population. The power was mainly controlled by the parameter stringency, that is, allowing for shorter ROH increased the power. The ROH-based individual measure of inbreeding F_ROH was highly correlated to F_IBD while also having regression coefficients close to 1 (i.e., a 1% variation in F_ROH corresponded to a 1% variation in F_IBD). Using stringent ROH parameters resulted in underestimation of the rate of inbreeding in the population. Increasing marker density improved predictions, including a higher true positive rate, power, higher correlations, and less underestimation of inbreeding rates.

This study aimed to evaluate the impact of different genomic prediction approaches on the predictive ability for meat tenderness in Nellore cattle. Phenotypic (n = 73,286), pedigree (n = 4,141,892) and genomic (n = 15,300) data from animals belonging to the genetic improvement program of the National Association of Breeders and Researchers (ANCP) were used. Six models were tested: (1) standard ssGBLUP (Single-step Genomic Best Linear Unbiased Prediction), considering direct additive genetic and residual effects as random, contemporary group (CG) as a fixed effect, and slaughter age as a linear and quadratic covariate; (2) Model 1 + ssGBLUP weighted with SNP effects from the first WssGWAS iteration; (3) Model 1 + ssGBLUP weighted with SNP effects from the second WssGWAS iteration; (4) Model 1 + body weight as a covariate; (5) Model 1 as a bi-trait model with body weight at 450 days (W450); (6) Model 1 as a multi-trait model with carcass traits: ribeye area (REA), backfat thickness (BFT) and rump fat thickness (RFT). Predictive ability was evaluated using linear regression, in which the dataset was divided into a complete and a partial subset (n = 374) dataset. Accuracy ranged from 0.04 (Models 2 and 3) to 0.37 (Model 6). Bias was low for all models, with Models 2 and 3 showing the least bias (-0.001). Model 6 showed the best performance in terms of accuracy and correlation (0.897), suggesting it was more effective in capturing genetic variability of meat tenderness, while reducing bias and increasing the precision of the estimates. Multi-trait models may offer more robust genomic predictions by leveraging trait correlations to increase prediction accuracy.

Procambarus acanthophorus is a freshwater crayfish species endemic to Mexico with high aquaculture potential. Monitoring genetic diversity during the early stages of domestication is crucial to avoid the erosion of adaptive potential and ensure the success of breeding programmes. This study analysed changes in genetic variability across four consecutive populations: a wild founder population (G0) and three captive-bred generations (G1, G2, G3), using five mitochondrial markers (COI, COII, COIII, tRNA-Asn/12S and D-loop) and one nuclear marker (elongation factor 2, EF-2). A total of 21 haplotypes were detected, with decreasing haplotype richness from G0 (n = 10) to G3 (n = 5), although haplotype and nucleotide diversity remained within moderate to high ranges (Hd = 0.65-0.90; π = 0.0020-0.0466), consistent with diversity levels reported in other early-stage domestication studies. AMOVA revealed that 68% of the total genetic variation was among generations, and pairwise Fst values confirmed progressive differentiation. These findings suggest that while some genetic erosion is occurring, the implemented breeding practices have preserved a substantial portion of genetic diversity during early domestication. This study provides a preliminary genetic baseline for the management of P. acanthophorus breeding programmes and underscores the need for continued monitoring using complementary nuclear markers.

Case history: In a 520-cow, spring-calving, pasture-based Waikato dairy farm, the bulk milk somatic cell count (SCC) increased by approximately 20% from 203,000 cells/mL in the 2020/21 season to 245,000 cells/mL in the 2021/22 season. Analysis of herd test SCC data found that the incidence of intramammary infection increased more than 10-fold from 1.8 to 19.2 cows/30 days at the March 2021 and March 2022 herd tests, respectively.

Laboratory findings: Milk sampling of all quarters of 43 cows with a SCC > 200,000 cells/mL following herd testing in March 2022, identified 12 quarters from 10 cows infected with Staphylococcus aureus. Antimicrobial sensitivity testing by disc diffusion testing found nine of these isolates (from seven cows) were methicillin resistant.

Diagnosis: Whole genome sequencing demonstrated the presence of mecA, a gene encoding an alternative penicillin-binding protein (PBP2a) associated with methicillin-resistant Staph. aureus (MRSA). These isolates were sequence type 5, spa type t002, and all were carrying one or more of the immune human immune evasion cluster genes, scn, chp, sak and sea.

Conclusions: Due to concerns for public safety, the Ministry for Primary Industries, the milk processor and the farm's staff were notified. A comprehensive management plan was implemented which focused on reducing the risk of human exposure by wearing gloves, discouraging consumption of raw milk, and smoking or eating in the milking parlour, alongside measures designed to minimise cow-to-cow transmission such as improving teat spray application, milking machine maintenance, additional sampling, and segregation of likely infected (that is, high SCC and confirmed presence of Staph. aureus) cows. Implementation of the plan resulted in a significantly lower bulk milk SCC and reduced incidence rate of new infections in the subsequent two lactations. However, MRSA was isolated from cows for at least a further 13 months, with some cows remaining infected this entire period despite having been treated with cloxacillin-based antimicrobials at the end of lactation. One staff member had a history of being hospitalised during 2021/22 for significant soft tissue infections.

Clinical relevance: Given the sequence type, spa type, and presence of the immune evasion cluster genes, it is probable that the MRSA was introduced into the herd from a human. Veterinarians need to be aware of the possibility of MRSA within dairy herds and the possible human origin for these infections.

Abbreviations: BMSCC: Bulk milk somatic cell count; MRSA: Methicillin-resistant Staphylococcus aureus; NAS: Non-aureus staphylococci; PBP: Penicillin-binding protein; SCC: Somatic cell count; spa: Staphylococcal protein A; ST: Sequence type.

Sucking lice (Anoplura) are highly specific parasites that depend extensively on their mammal hosts for survival. However, the climate to which their hosts are exposed can cause changes in their populations, independent of the protection provided by their hosts. Despite its harsh climate, arid northern Chile is home to a wide variety of rodents, particularly cricetids. This area comprises four distinct ecoregions with different sub-climates. We aimed to evaluate the spatial and seasonal variability of sucking lice (Anoplura) parasitizing rodents in northern Chile. Specifically, we analysed the association of environmental variables and host density with the louse point prevalence (P%), mean abundance (_MA) and mean infestation intensity (_MI). Rodent samples were collected during autumn and spring of 2011 and summer and winter of 2012 in 13 sites representative of the Coastal Desert (CD), Continental (Interior) Desert (ID), Andean Tropical (AT) and Pre-Andean Tropical (PAT) ecoregions. A total of 992 rodents of eight species were captured and anaesthetized, and lice were collected and identified. The P%, _MA and _MI of lice were estimated. The association of climatic variables (temperature, precipitation and relative humidity) and host density (capture success as a proxy) with louse P% and _MA was assessed using Spearman correlation and Fisher's test. Four lice species were identified based on external morphology (Hoplopleuridae: Hoplopleura aitkeni Johnson, Hoplopleura reducta Ferris, Hoplopleura sp. travassosi group; Poliplacidae: Polyplax spinulosa (Burmeister)). Hoplopleura aitkeni and H. reducta showed significant seasonal differences in P%, _MA and _MI in the AT and PAT ecoregions. In contrast, the H. sp. travassosi group showed no significant seasonal variation. Polyplax spinulosa was found exclusively on introduced rodents in the ID ecoregion, with distinct seasonal variations observed in Rattus norvegicus Berkenhout and Rattus rattus Linnaeus (Muridae). We reported 17 new host-parasite associations, and one lice species not previously described in the country. This study demonstrates that seasonal environmental variation does not equally impact all lice species, emphasizing the need for further research into the ecological and biological drivers of these dynamics.

This case describes the diagnosis and treatment of a bilateral caudoventral temporomandibular joint (TMJ) luxation in a 7-year-old intact male Persian cat following a fall from the fourth floor of a building. The patient sustained traumatic brain injury and dental fractures. Diagnostic imaging, including intraoral radiographs and computed tomography, confirmed a bilateral caudoventral TMJ luxation. Surgical intervention was delayed for 10 days due to the patient's neurological status, limiting the chances for a successful joint reduction. A modified surgical approach facilitated precise localization of the condylar process and minimized morbidity. Postoperative outcome was favorable, with the patient resuming voluntary eating within 5 days. Timely and accurate treatment is essential for the successful restoration of joint function in feline patients suffering from traumatic dislocation of the TMJ. This is particularly critical in brachycephalic breeds, which may have a predisposition to such injuries.

Human epidermal growth factor receptor 2 (HER2) gene mutations have been reported in 5% to 38% of canine pulmonary adenocarcinomas (cPACs), most commonly as V659E mutations in exon 20. However, their prognostic and predictive significance remains unclear. This retrospective, single-centre cohort study investigated the frequency of HER2 mutations in surgically resected cPACs and their association with clinical outcomes. Between 2005 and 2021, lung masses histologically diagnosed as cPACs were collected and subjected to direct sequencing of HER2 exons 20 and 21. A total of 72 dogs were enrolled, with successful HER2 gene analysis in 69 cases. HER2 exon 20 missense mutations were identified in 20 dogs (29.0%), including 18 harbouring the previously reported V659E hotspot mutation within the transmembrane domain. Homozygous mutations were detected in 13 dogs. Univariable analysis revealed associations between progression-free interval (PFI) and clinical signs, tumour size classification, lymph node metastasis, surgical margin status, and histologic grade. Overall survival time (OST) was associated with age, clinical signs, tumour size > 7 cm, histologic subtype, lymph node metastasis, and margin status. In multivariable analysis, tumour size classification and margin status remained significantly associated with PFI, while age, tumour size > 7 cm, and histologic subtype were independently associated with OST. Notably, the presence of HER2 mutations was significantly associated with prolonged PFI in both univariable and multivariable analyses, although no significant association with OST was observed. These findings suggest that HER2 mutation status may serve as a favourable prognostic marker for disease progression in surgically resected cPACs.

In the summer of 2023 in southern Brazil, there was a fatal outbreak of acute gastrointestinal disease in calves that ingested Titya abstersa caterpillars. The outbreak affected 6 of the 40 calves raised in an extensive system, with a mortality rate of 15%. The clinical signs included anorexia, hypersalivation, ruminal bloat, fever (39.8-40.5°C), polydipsia, and gastric reflux. Death occurred within 24 to 48 hours after the onset of the clinical signs. Macroscopic and microscopic findings revealed necrotic rumenitis, reticulitis, esophagitis, and longitudinal and transverse sections of golden structures with backward-facing barbs, consistent with intralesional caterpillar setae. This study aimed to characterize the clinical, epidemiological, and pathological aspects from the necropsies of 3 affected calves. To date, there have been no similar reports regarding the ingestion of T. abstersa caterpillars.

Oral mucosal melanomas (OMMs) are the most frequent oral malignancy in dogs, often characterized by aggressive local behavior and a high metastatic rate. The mechanisms that drive canine OMM metastasis are still largely unknown, providing for limited therapeutic approaches once the disease has spread to metastatic sites. The objective of this investigation was to evaluate the differences in gene expression between canine primary OMMs and their matched nodal metastases. Transcriptional profiling of formalin-fixed, paraffin-embedded biopsies of 4 canine OMMs and their respective lymph node biopsies was performed using exon microarrays. Confirmation of the differential expression of selected genes was subsequently sought by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) on 13 paired samples (primary tumor-metastatic lymph node). Results highlight the activation of pathways associated with actin cytoskeleton organization, and cellular motility and migration. In particular, transcriptional data indicated increased expression of genes associated with Rac1 signaling-regulated cell migration, including ELMO1, VAV3, and DOCK2, in nodal metastases. Overall, the results of this investigation point to a significant role for Rac1 signaling in the pathogenesis of OMM metastasis to regional lymph nodes. The Rac1 signaling-associated genes highlighted herein are indeed involved in the activation of cellular migration, and one, or more, may represent a future therapeutic target to prevent metastatic dissemination, or treat OMM with distant metastases.

Intracytoplasmic inclusions in atrial cardiomyocytes of guinea pigs were incidentally identified on routine postmortem evaluation. This study was conducted to assess their location, incidence, morphology, staining properties, ultrastructural appearance, epidemiological characteristics, and pathologic significance. Retrospective cases from 2014 to 2022 with right and/or left atria sampled for histologic examination were selected, and hearts of guinea pigs necropsied in 2023 were systematically formalin-fixed and included. Inclusions were identified in 27 of 28 animals (96%). They were significantly more numerous in the right atrium compared with the left atrium (P < .001, Wilcoxon signed-rank test) and preferentially located as clusters in the subendocardial region. None of these inclusions were detected in the ventricular myocardium. These inclusions were intracytoplasmic, ovoid to linear, frequently fragmented, slightly basophilic to amphophilic in hemalum, eosin, and saffron-stained sections and measured from 1 to 130 µm in length. They stained positively with periodic acid-Schiff, Gomori-Grocott's methenamine silver, and Alcian blue pH 2.5; negatively or unstained with Alcian blue pH 1, toluidine blue, von Kossa, Congo red, and Masson's trichrome; and were amylase resistant. Transmission electronic microscopy revealed slightly electron-dense, non-membrane-bound aggregates of filaments interspersed with granular material compatible with polyglucosan bodies. Animals under 1-year-old had significantly fewer inclusions than older animals (P = .002, Mann-Whitney U test). Inclusion density in the right atrium was not associated with sex, body weight, local heart lesions, or cardiac or systemic disease. Those features are similar to a human condition named basophilic degeneration, reported here for the first time in guinea pigs.