Associations among antimicrobial use, calf management practices, and antimicrobial resistance in Escherichia coli from a pooled fecal sample in calves on Canadian dairy farms: A cross-sectional study.

The objective of this cross-sectional study was to determine associations between calf management practices, the number of antimicrobial treatments, and antimicrobial resistance in preweaning heifers on Canadian dairy farms. A composite of 5 fecal samples from preweaning calves was collected from 142 dairy farms in 5 provinces and analyzed for phenotypic antimicrobial susceptibility with the microbroth dilution method. Questionnaires were used to capture herd characteristics and calf management practices used on the farm. Calf treatment records were collected during the farm visits. Escherichia coli was isolated from all 142 fecal samples with the highest resistance to tetracycline (41%), followed by sulfisoxazole (36%), streptomycin (32%), chloramphenicol (28%), ampicillin (16%), trimethoprim-sulfamethoxazole (15%), ceftriaxone (4.2%), cefoxitin (2.8%), amoxicillin-clavulanic acid (2.1%), ciprofloxacin (2.1%), nalidixic acid (2.1%), azithromycin (1.4%), and gentamicin (1.4%). Multidrug resistance was observed in 37% of E. coli isolates. Three-quarters of farms used fresh colostrum as the most common type of colostrum fed to calves. Colostrum quality was checked on 49% of farms, but the transfer of passive immunity was only checked on 32% of farms in the last 12 mo. Almost 70% of farms used straw or hay or a combination as the bedding material for calves. Among the 142 farms, a complete set of calf records were collected from 71 farms. In a multivariable logistic regression model, farms with ≥1.99 to 32.57 antimicrobial treatments/calf-year were 3.2 times more likely to have multidrug resistant E. coli in calf feces compared farms with <1.99 antimicrobial treatments/calf-year. Farms using hay or straw beddings were 5.1 times less likely to have multidrug resistant E. coli compared with those with other bedding materials including shavings or sawdust. Bedding management practices on farms may need to be investigated to reduce the potential effect on disseminating multidrug resistant bacteria.

Associations of calf management practices with antimicrobial use in Canadian dairy calves.

The objective of this cross-sectional study was to investigate the relationship between management practices and antimicrobial use in heifer calves on Canadian dairy farms. Questionnaires on calf management practices, herd characteristics, and calf treatment records were administered on 147 dairy farms in 5 provinces during annual farm visits in a multiyear, nationwide research project (Canadian Dairy Network for Antimicrobial Stewardship and Resistance: CaDNetASR). Questions focused on the calf caregiver, calving pen, colostrum management, milk feeding, grouping, bedding management, and age when male calves were sold. Antimicrobial treatment records were collected on each farm from either an electronic herd management system or paper-based records. Newborn heifers born in the last 12 mo were identified retrospectively and followed to 60 d of age, with antimicrobial treatments and dates of sale or death extracted for further analysis. A multivariable linear regression model was developed with the natural log of the number of antimicrobial treatments per calf-year as the dependent variable, and categorized calf management practices and farm characteristics as the independent variables. A complete data set of records on 7,817 calves was retrieved from 74 farms based on completeness of calf records. A total of 2,310 calves were treated at least once with an antimicrobial, and 7,307 individual antimicrobial treatments were recorded. Among the reasons for antimicrobial use, respiratory disease (54%) was most common, followed by diarrhea (20%), presence of a fever (3%), and umbilical disease (2%). Florfenicol (33% of recorded treatments), penicillin (23%), and trimethoprim-sulfamethoxazole (18%) were commonly used, whereas fluoroquinolones (4%), and ceftiofur (1%) were used less commonly. Farms (31%) commonly had 0-1.0 antimicrobial treatments/calf-year (median: 2.2 treatments/calf-year; interquartile range: 0.64-6.43 treatments/calf-year). Defined daily dose (DDD) per calf-year was calculated based on the Canadian bovine standards. Among the 74 farms, florfenicol (1.35 DDD/calf-year) and macrolides (0.73 DDD/calf-year) were used most, whereas ceftiofur (0.008 DDD/calf-year) was the lowest. The final multivariable linear regression model indicated that farms that fed transition milk had fewer than half the number of antimicrobial treatments per calf-year than those who did not feed transition milk. The number of antimicrobial treatments per calf-year in preweaning calves was low on many farms, and there was low use of highly important drugs for human medicine. The effect of feeding transition milk should be investigated regarding potential effects on antimicrobial use and disease prevention.

Occurrence of extended-spectrum ß-lactamase and AmpC-producing Escherichia coli in retail meat products from the Maritime Provinces, Canada.

This study was conducted to determine the occurrence of antimicrobial resistance to the extended-spectrum cephalosporins (ESC) in Escherichia coli isolates. The isolates were collected from retail meat products collected in the Maritime Provinces of Canada. Our analyses involved the use of both selective and traditional culture methods; we also conducted genotype analyses using multiplex polymerase chain reactions. ESC-resistant (ESC-R) E. coli were detected in 33 of 559 samples (5.9%) using the traditional culture method, compared with 151 of 557 samples (27.1%) using the selective culture method. We recovered more isolates of ESC-R E. coli from poultry compared with beef and pork (P < 0.001). Multidrug resistance, extended-spectrum ß-lactamase (ESBL), and AmpC phenotypes were more common in chicken-derived isolates than other retail meat products (P < 0.001). From the 98 isolates examined, 76 isolates (77.6%) were positive for either ESBL and AmpC ß-lactamases or both. Among the 76 isolates, blaCMY-2 (78.9%), blaCTXM (46.1%), blaTEM (21.1%), and blaSHV (1.3%) genes were detected. Among the blaCTXM-producing isolates, blaCTXM-1, blaCTXM-2, and blaCTXM-9 phylogenetic groups were detected. ß-lactamase genes were more commonly detected in chicken-derived isolates compared with other meat types (P < 0.01). This study demonstrates the occurrence of ESBL- and AmpC-resistance genes in retail meat products in the Maritime Provinces of Canada. We found that selective culture significantly improved the recovery of ESC-R E. coli isolates from retail meat samples.

Accuracy of direct and indirect methods for assessing bovine colostrum quality using a latent class model fit within a Bayesian framework.

Feeding high-quality colostrum is essential for calf health and future productivity. Therefore, accurate assessment of colostrum quality is a key component of dairy farm management plans. Direct and indirect methods are available for assessment of colostrum quality; however, the indirect methods are rapid, inexpensive, and can be performed under field settings. A hierarchical latent class model fit within a Bayesian framework was used to estimate the sensitivity (Se) and specificity (Sp) of the radial immunodiffusion (RID) assay, transmission infrared (TIR) spectroscopy, and digital Brix refractometer for the assessment of low-quality bovine colostrum in Atlantic Canada dairy herds. The secondary objective of the study was to describe the distribution of herd prevalence of low-quality colostrum. Colostrum quality of 591 samples from 42 commercial Holstein dairy herds in 4 Atlantic Canada provinces was assessed using RID, TIR spectroscopy, and digital Brix refractometer. The accuracy of all tests at different Brix value thresholds was estimated using Bayesian latent class models to obtain posterior estimates [medians and 95% Bayesian credibility intervals (95% BCI)] for each parameter. Using a threshold of <23% for digital Brix refractometer and <50 g/L for RID and TIR spectroscopy, median (95% BCI) Se estimates were 73.2 (68.4-77.7), 86.2 (80.6-91.0), and 91.9% (89.0-94.2), respectively. Median (95% BCI) Sp estimates were 85.2% (81.0-88.9) for digital Brix refractometer, 99.4% (97.0-100) for RID, and 90.7% (87.8-93.2) for TIR spectroscopy. Median (95% BCI) within-herd low-quality colostrum prevalence was estimated at 32.5% (27.9-37.4). In conclusion, using digital Brix refractometer at a Brix threshold of <23% could reduce feeding of low-quality colostrum to calves and improve colostrum and calf management practices in Atlantic Canada dairy herds. The TIR spectroscopy showed high Se in detection of low-quality colostrum. However, the RID assay, which is used as the reference test in several studies, showed limited Se for detection of low-quality colostrum.

Characterization of the microbiota and resistome of bulk tank milk samples from Prince Edward Island dairy farms.

Bulk tank milk (BTM) is regularly used for surveillance on dairy farms for disease conditions such as mastitis and Johne's disease. In this study, we used 16S rRNA sequencing and bait-capture enrichment to characterize the microbiota and resistome of BTM, and investigate potential differences between the cream or pellet fractions. A total of 12 BTM samples were taken from 12 Prince Edward Island dairy farms, in Atlantic Canada, in duplicates. The DNA was analyzed by high-throughput sequencing of the 16S rRNA gene and a suite of antimicrobial resistance (AMR) genes. Target-capture enrichment of AMR genes was conducted before shotgun sequencing. The bioinformatics pipelines QIIME 2 and AMR++ were used for microbiota and resistome analysis, respectively. Differences between microbiotae were evaluated qualitatively with nonmetric multidimensional scaling and quantitatively with permutational ANOVA of UniFrac distances. A total of 47 phyla were present across the BTM samples. Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria were the most abundant phyla. At the genus level, Corynebacterium, Acinetobacter, Lactobacillus, and Turicibacter were the most abundant. There was no significant difference in the Faith's phylogenetic diversity between the cream and pellet fraction. Faith's phylogenetic diversity differed marginally by stall type. There were 10,217 hits across 80 unique AMR genes, with tetracycline resistance being the most common class.

Development and implementation of a risk assessment and management program for enzootic bovine leukosis in Atlantic Canada.

Over the past 30 yr, the prevalence of bovine leukemia virus (BLV) infection has increased in North America, including Atlantic Canada, at both the herd and individual cow levels. This has occurred despite increased awareness of the disease and its deleterious effects and despite implementation of management practices aimed at reducing disease transmission. Our objectives were to identify risk factors associated with the within-herd prevalence of BLV-infected cows by using a risk assessment and management program workbook, as well as to determine the current level of BLV prevalence in the Atlantic Canada region. We hypothesized that previously established risk factors, including management practices associated with calf rearing and fly control, would affect within-herd BLV prevalence. Bulk tank milk (BTM) samples were collected in January and April of 2016 and again during the same months in 2017 and 2018 from all dairy farms shipping milk in the region. Samples were tested with ELISA for levels of anti-BLV antibodies to estimate within-herd prevalence. Regional BLV prevalence at the herd level was 88.39% of dairy herds infected in 2016 and 89.30% in 2018. All dairy farms shipping milk and who had BTM samples collected in 2017 (n = 605) were eligible to participate in the risk assessment and management program questionnaire (RAMP), which was developed and distributed to all bovine veterinarians in Atlantic Canada. One hundred and six RAMP were returned, with representation from all 4 provinces. The RAMP results were combined with the mean BTM ELISA results, and univariable logistic regression followed by multivariable logistic regression was performed to investigate the association between RAMP risk factors and the estimated within-herd BLV prevalence. Factors in the multivariable model significantly associated with the odds of a herd being classified as >25% estimated within-herd prevalence included history of diagnosis of clinical BLV and calves receiving colostrum from cows with unknown BLV status. Differences in within-herd prevalence were not associated with hypodermic needle and injection practices, rectal sleeve practices, or using bulls for natural breeding, based on these 106 dairy farms.

Using serum and plasma samples to assess failure of transfer of passive immunity in dairy calves.

The objectives of this study were (1) to determine the differences in IgG and total protein (TP) content of serum and plasma samples collected from the same calves; (2) to evaluate the correlation between calf serum and plasma IgG levels, Brix scores, and TP concentrations; (3) to determine whether different cut-off values should be used for plasma and serum to assess failure of transfer of passive immunity (FTPI) in dairy calves; and (4) to evaluate the level of agreement between results obtained from using serum and plasma samples of the same calves to assess FTPI using optimal cut-off values. Blood samples (n = 217) were collected from Holstein calves at 3 to 10 d of age on 30 commercial dairy farms in Nova Scotia and Newfoundland, Canada. Paired serum and plasma samples were analyzed for IgG concentration by the reference radial immunodiffusion assay, transmission infrared (TIR) spectroscopy, digital and optical Brix refractometers, and optical TP refractometer. The IgG concentrations measured by RID and TIR spectroscopy in serum were similar to those in plasma. However, the Brix and TP refractometer readings were significantly higher in plasma than in serum. The prevalence of FTPI in serum and plasma samples based on a RID-IgG concentration <10 g/L was 43.3 and 46.5%, respectively. The RID-IgG concentration was correlated with TIR-IgG (r = 0.92 and 0.89), digital Brix (r = 0.80 and 0.80), optical Brix (r = 0.77 and 0.77), and optical TP (r = 0.75 and 0.77) refractometers in serum and plasma, respectively. The correlations between paired serum and plasma IgG content were 0.85 by TIR spectroscopy, 0.80 by digital Brix, 0.77 by optical Brix, and 0.79 by optical TP refractometer. The optimal cut-off values for TIR spectroscopy, digital Brix, optical Brix, and TP refractometers to assess FTPI using serum were 13.1 g/L, 8.7% Brix, 8.4% Brix and 5.1 g/dL, respectively; and the optimal cut-off values with plasma were 13.4 g/L, 9.4% Brix, 9.3% Brix and 5.8 g/dL, respectively. When using these optimal cut-off values, the level of agreement (88.1%) between results derived from testing serum and plasma by TIR spectroscopy was substantial, with a kappa (κ) value of 0.76. The results derived from testing serum and plasma by digital Brix refractometer showed substantial agreement (83.4%), with a κ value of 0.65, which is higher than the agreement and κ value (74.7% and 0.51) reported for the optical Brix refractometer. Substantial agreement (81.6%) between serum and plasma TP was also obtained when using the optical TP refractometer, with a κ value of 0.63. In conclusion, serum or plasma samples can be used interchangeably for measuring IgG concentrations and assessing FTPI in dairy calves. However, different cut-offs must be used to assess FTPI depending on the sample matrix. Furthermore, results obtained from serum samples showed higher agreement with the reference RID assay than those obtained from plasma samples.

Observational study on the occurrence of surgical glove perforation and associated risk factors in large animal surgery.

OBJECTIVE: To determine the incidence of and associated risk factors for glove perforation in large animal surgery. STUDY DESIGN: Prospective observational cohort study. SAMPLE POPULATION: Surgical gloves (n = 917) worn during 103 large animal surgical procedures. METHODS: Gloves worn by personnel involved in sterile preparation and surgical procedures were tested for perforation by 2 previously validated methods, water leak test (WLT) and electroconductivity testing (ECT). The association between surgical and glove-related variables and glove perforation was assessed by using a multivariable mixed-effect logistic regression model. RESULTS: At least 1 glove perforation was detected in 66% of surgical procedures, and 17.9% (164/917) of gloves tested were identified as perforated. All perforations were detected by ECT, whereas only 110/178 (61.8%) were detected by WLT. All perforations detected by WLT were also detected by ECT. The risk of glove perforation increased with duration of wear (>60 minutes odds ratio [OR] 2.3, 95% CI 1.4-3.7; P < .001) and with invasiveness of procedures (OR 7.9, 95% CI 3.2-19.5; P < .001). Primary surgeons were at higher risk for glove perforation than first (OR 1.7, 95% CI 1.1-2.5; P = .008) and second (OR 3.4, 95% CI 2-6.7; P < .001) assistants. Only 25% of glove perforations were detected intraoperatively by the wearer. CONCLUSION: Incidence of glove perforation is similar in large animal, human, and small animal surgery and is influenced by duration of wear, invasiveness of the surgery, and role of the wearer. ECT is more sensitive than WLT for detection of glove perforation.

Antimicrobial resistance in bacteria isolated from horses from the Atlantic Provinces, Canada (1994 to 2013).

This study determined the antimicrobial susceptibility patterns and trends for selected bacteria isolated from horses using diagnostic data from the Atlantic Veterinary College Diagnostic Services Bacteriology Laboratory, Charlottetown, Prince Edward Island over a 20-year period. Streptococcus equi subsp. zooepidemicus and Escherichia coli were the most commonly isolated bacteria over the study period. Clinical samples were most frequently submitted from respiratory and reproductive systems. Most bacterial isolates were susceptible to ceftiofur. Resistance was most common in Gram-negative enteric bacteria, while streptococci were frequently susceptible to most of the antimicrobials tested including penicillin and trimethoprim-sulfamethoxazole. The antimicrobial resistance trends over the study period were relatively stable. Multi-drug resistance was observed in 9% of the bacterial isolates. Information provided in this study could be used to help guide rational, empirical antimicrobial treatment selection in equine practices in Atlantic Canada.

Résistance aux antimicrobiens dans les bactéries isolées des chevaux dans les provinces de l'Atlantique, au Canada, de 1994 à 2013. Cette étude a déterminé les modèles et les tendances de susceptibilité antimicrobienne pour certaines bactéries isolées des chevaux en s'appuyant sur des données diagnostiques du Laboratoire de bactériologie des services diagnostiques de l'Atlantic Veterinary College à Charlottetown, à l'Île-du-Prince-Édouard, pendant une période de 20 ans. Streptococcus equi ssp. zooepidemicus et Escherichia coli ont été les bactéries les plus communément isolées pendant la période à l'étude. Des échantillons cliniques des systèmes respiratoires et reproducteurs étaient les plus fréquemment soumis. La plupart des isolats bactériens étaient susceptibles au ceftiofur. La résistance était la plus courante chez les bactéries entériques à Gram négatif, tandis que les streptocoques étaient fréquemment susceptibles à la plupart des antimicrobiens testés incluant la pénicilline et le triméthoprime-sulfaméthoxazole. Les tendances de résistance aux antimicrobiens pendant la période à l'étude étaient relativement stables. Une multirésistance aux médicaments a été observée dans 9 % des isolats bactériens. Les renseignements fournis dans cette étude pourraient servir à guider un choix rationnel et empirique pour les traitements antimicrobiens dans les pratiques équines des provinces de l'Atlantique.(Traduit par Isabelle Vallières).

Antimicrobial resistance in mastitis, respiratory and enteric bacteria isolated from ruminant animals from the Atlantic Provinces of Canada from 1994-2013.

Diagnostic laboratory antimicrobial susceptibility data for bacteria isolated from clinical samples of cattle, sheep, and goats from 1994 to 2013 were evaluated retrospectively. Among bacteria from bovine mastitis, Staphylococcus aureus and Streptococcus uberis were the most commonly isolated organisms. Pasteurella multocida, Mannheimia haemolytica, and Histophilus somni were commonly isolated from the respiratory tract, while Escherichia coli isolates were frequently recovered from the intestinal tract. Isolates from mastitis were generally highly susceptible to the antimicrobials tested, except neomycin and oxytetracycline. Respiratory tract isolates were highly susceptible to trimethoprim-sulfamethoxazole, penicillin, florfenicol, and ceftiofur, while enteric bacteria were frequently susceptible to ceftiofur. Antimicrobial resistance trends over the study period were generally stable for small ruminant and cattle isolates. Multi-drug resistance was more common among respiratory isolates from small ruminants compared to those from cattle but more common in enteric bacteria from cattle compared to those from small ruminants. This information may guide clinicians when they are choosing empirical therapies for the treatment of ruminant animals in Atlantic Canada.

Résistance antimicrobienne des bactéries respiratoires et entériques et de la mammite isolées des ruminants dans les provinces de l'Atlantique de 1994 à 2013. Les données de susceptibilité antimicrobienne des laboratoires diagnostiques, de 1994 à 2013, pour les bactéries isolées d'échantillons cliniques de bovins, de moutons et de chèvres, ont été évaluées rétrospectivement. Parmi les bactéries trouvées en lien avec la mammite bovine, Staphylococcus aureus et Streptococcus uberis ont été les organismes les plus communément isolés. Pasteurella multocida, Mannheimia haemolytica et Histophilus somni ont été communément isolés de l'appareil respiratoire, tandis que des isolats d'Escherichia coli étaient fréquemment récupérés du tractus intestinal. Les isolats de la mammite étaient généralement hautement susceptibles aux antimicrobiens testés, sauf pour la néomycine et l'oxytétracycline. Les isolats de l'appareil respiratoire étaient hautement susceptibles au triméthoprime-sulfaméthoxazole, à la pénicilline, au florfénicol et au ceftiofur, tandis que les bactéries entériques étaient fréquemment susceptibles au ceftiofur. Les tendances d'antibiorésistance pendant la période de l'étude étaient généralement stables pour les isolats des petits ruminants et des bovins. La multirésistance aux médicaments était plus commune pour les isolats respiratoires provenant des petits ruminants comparativement à ceux des bovins et plus commune dans les bactéries entériques des bovins par rapport à celles des petits ruminants. Ces données pourront guider les cliniciens qui choisissent des thérapies empiriques pour le traitement des ruminants dans les provinces de l'Atlantique.(Traduit par Isabelle Vallières).

Rapid assessment of bovine colostrum quality: How reliable are transmission infrared spectroscopy and digital and optical refractometers?

The objectives of this study were to evaluate the performance of the transmission infrared (IR) spectroscopic method and digital and optical Brix refractometers for measurement of colostral IgG concentration and assessment of colostrum quality of dairy cows. Colostrum samples (n = 258) were collected from Holstein cows on 30 commercial dairy farms in Nova Scotia and Newfoundland, Canada. Colostral IgG concentrations of 255 samples were measured by the reference radial immunodiffusion (RID) assay and IR spectroscopy. The Brix scores were determined on 240 of these samples using both the digital and optical Brix refractometers. Approximately half (48%) of the colostrum samples had RID IgG concentrations <50 g/L, which was the cut-point for poor quality. The correlation between RID and IR IgG concentrations was 0.88. The correlations between RID IgG concentration and Brix scores, as determined by the digital and optical refractometers, were 0.72 and 0.71, respectively. The optimal cutoff levels for distinguishing good- and poor-quality colostrum using IR spectroscopy, and digital and optical Brix refractometers were at 35 g/L and 23% Brix, respectively. The IR spectroscopy showed higher sensitivity (90%) and specificity (86%) than the digital (74 and 80%, respectively) and optical (73 and 80%, respectively) Brix refractometers for assessment of colostrum quality, as compared with RID. In conclusion, the transmission-IR spectroscopy is a rapid and accurate method for assessing colostrum quality, but is a laboratory-based method, whereas Brix refractometers were less accurate but could be used on-farm.

Short communication: Extended-spectrum cephalosporin-resistant Escherichia coli in colostrum from New Brunswick, Canada, dairy cows harbor blaCMY-2 and blaTEM resistance genes.

Dairy calves are colonized shortly after birth by multidrug resistant (MDR) bacteria, including Escherichia coli. The role of dairy colostrum fed to calves as a potential source of MDR bacteria resistance genes has not been investigated. This study determined the recovery rate of extended-spectrum cephalosporin-resistant (ESC-R) E. coli in colostrum from cows. The ESC-R E. coli isolates were further investigated to determine their phenotypic antimicrobial resistance pattern and the genes conferring ESC-R. Fresh colostrum was collected from 452 cows from 8 dairy herds in New Brunswick, Canada. The ESC-R E. coli was isolated from the colostrum by using the VACC agar, a selective media for extended-spectrum ß-lactamase producing Enterobacteriaceae. Minimum inhibitory concentration was determined for all the suspected ESC-R E. coli isolates using a commercial gram-negative broth microdilution method. Two multiplex PCR were conducted on all the suspected ESC-R E. coli isolates to determine the presence of the blaCTX-M (groups 1, 2, 9, and 8/25) blaCMY-2, blaSHV, and blaTEM resistance genes. The ESC-R E. coli were detected in 20 (4.43%) of the colostrum samples. At least 1 ESC-R E. coli isolate was detected in 6 (75%) of the dairy herds. All ESC-R E. coli had MDR profiles based on minimum inhibitory concentration testing. No blaCTX-M groups genes were detected; however, the blaCMY-2 gene was detected in 9 or 20 (45%) and blaTEM was detected in 7 of 20 (35%) of the ESC-R E. coli. No ESC-R E. coli had both blaCMY-2 and blaTEM resistance genes. This is the first report of blaCMY-2 and blaTEM genes found in E. coli isolates cultured from dairy colostrum to our knowledge.

Occurrence and antimicrobial resistance of Escherichia coli in oysters and mussels from Atlantic Canada.

Acquiring antimicrobial-resistant (AMR) bacteria through consuming contaminated animal food products is an emerging public health concern, though the sources of contamination are not always clear. This study characterized the occurrence of AMR in Escherichia coli from bivalve molluscs and assessed for the possible sources in the Hillsborough river complex of Prince Edward Island, Canada in areas overlapping with an oyster fishery. Multivariable statistical analysis indicated that the probability of detecting E. coli increased as the estimated dosage of animal effluent contamination decreased. Isolates with AMR were only found from sampling sites closest to untreated human effluent sources. Twenty-seven percent (n=6 of 22) of the isolates were pathogenic, with virulence factors consistent with extraintestinal E. coli of human origin. Though there is more evidence of contamination arising from human effluent, more research is needed to identify driving sources.

Listeria monocytogenes cholangiohepatitis in a lactating Holstein cow.

OBJECTIVE: To describe a unique presentation of systemic Listeria monocytogenes infection in a lactating adult Holstein cow. ANIMAL: 3-year-old second-parity female Holstein, 200 days in milk. CLINICAL PRESENTATION, PROGRESSION, AND PROCEDURES: A 3-year-old Holstein dairy cow was presented for decreased appetite, decreased milk production, and pyrexia. Blood work displayed marked abnormalities in liver-associated parameters. A diagnosis of L monocytogenes cholangiohepatitis was made following liver biopsy, histopathology, and bacterial culture. TREATMENT AND OUTCOME: The cow was treated with systemic antimicrobial and antipyretic therapy. The cow was discharged to continue treatment on farm, and at time of last communication with the owner, the cow was doing very well, with full resolution of clinical signs. CLINICAL RELEVANCE: This case report describes a novel presentation of L monocytogenes infection in an adult bovine. L monocytogenes cholangiohepatitis should be considered a rare differential diagnosis in cattle presenting with evidence of pyrexia and liver disease.

The associations of early-life health and performance with subsequent dairy cow longevity, productivity, and profitability.

Selecting and raising dairy animals that are more likely to reach their potential is a strategy to increase milk production efficiency and overall profitability. However, indicators are necessary for the early identification of animals that are less likely to perform well, allowing for their early culling and ensuring that resources are allocated to those with the highest potential. The objective of this study was to analyze the association between early-life animal health and performance with longevity, production, and profitability. After data cleaning, the following early-life measures (i.e., predictors) were available for 363 female calves born between June 2014 and November 2015 in eight dairy herds from New Brunswick, Canada (average: 45 calves/farm; SD: 26.1 calves/farm; median: 42 calves/farm; range: 15-95 calves/farm): birth weight, weaning weight, weaning age, weaning average daily gain (weaning ADG), immunoglobulin G (IgG) serum concentration, the occurrence of navel infection, diarrhea, and pneumonia, and if animals received antibiotic treatment between birth and weaning. Their subsequent length of life (LL), length of productive life (LPL), lifetime cumulative energy-corrected milk (ECM), and lifetime cumulative milk value (i.e., response variables) were provided by the Canadian dairy herd improvement agency. Bayesian Additive Regression Tree models were trained for each response variable using 5-fold cross-validation. Models were evaluated using the RMSE and R2. The three most important predictors were identified using permutation, and the relationship between response variables and important predictors was assessed using accumulated local effect plots. The RMSE for LL, LPL, ECM, and milk value were 1.43 years, 1.37 years, 16 314.94 kg, and $CAD 11 525.68, respectively, whereas the R2 values were 0.30, 0.25, 0.29, and 0.29, respectively, indicating a moderate relationship between predictors and response variables. Non-linear relationships were found between the response variables and important predictors. Animals born with low or high birth weights were associated with decreased LL, LPL, ECM, and milk value. The highest LL, LPL, and milk value was observed for calves weaned between 1.9 and 2.0 months old, followed by a decline for calves weaned at older ages. The lowest LL and ECM were associated with weaning ADG of 0.786 kg/day, while 0.787 kg/day was associated with the lowest LPL. Lastly, both ECM and milk value were highest when serum IgG values were 1 659 mg/dL. These findings provide valuable insights for optimizing early culling decisions and enhancing the productivity and profitability of dairy farms.

Effects of storage conditions on the microbiota of fecal samples collected from dairy cattle.

Microbiota analyses are key to understanding the bacterial communities within dairy cattle, but the impact of different storage conditions on these analyses remains unclear. This study sought to examine the effects of freezing at -80°C immediately after collection, refrigeration at 4°C for three days and seven days and absolute ethanol preservation on the microbiota diversity of pooled fecal samples from dairy cattle. Examining 16S rRNA gene sequences, alpha (Shannon, Pielou evenness, observed features and Faith PD indices) and beta (Bray-Curtis, ßw and Weighted UniFrac) diversity were assessed. The effects of storage conditions on these metrics were evaluated using linear mixed models and PERMANOVA, incorporating the farm as a random effect. Our findings reveal that 7d and E significantly altered the Shannon index, suggesting a change in community composition. Changes in Pielou evenness for 3d and 7d storage when compared to 0d were found, indicating a shift in species evenness. Ethanol preservation impacted both observed features and Faith PD indices. Storage conditions significantly influenced Bray-Curtis, ßw, and Weighted UniFrac metrics, indicating changes in community structure. PERMANOVA analysis showed that these storage conditions significantly contributed to microbiota differences compared to immediate freezing. In conclusion, our results demonstrate that while refrigeration for three days had minimal impact, seven days of refrigeration and ethanol preservation significantly altered microbiota analyses. These findings highlight the importance of sample storage considerations in microbiota research.

Differences in diversity and community composition of the shell microbiome of apparently healthy lobsters Homarus americanus across Atlantic Canada.

Host-microbe dynamics are of increasing interest in marine research due to their role in host health and productivity. Changes in the shell microbiome of American lobsters have been associated with epizootic shell disease, a syndrome that is spreading northwards across the eastern U.S. and Canadian Atlantic coast. This study analyzed differences in alpha and beta diversity, as well as differentially abundant taxa, in the shell-associated bacterial community of apparently healthy lobsters from four lobster fishing areas (LFAs) in Atlantic Canada. Over 180 lobsters from New Brunswick, Nova Scotia and Prince Edward Island (PEI) were sampled during seven sampling events over four sampling months. The bacterial community was identified using novel PacBio long-read sequencing, while alpha and beta diversity parameters were analyzed using linear regression models and weighted UniFrac distances. The bacterial richness, diversity and evenness differed by sampling location, sampling month, and molt stage, but not by lobster sex or size, nor sampling depth. Similarly, based on LFA, sampling month, year and lobster molt stage, the shell microbiome differed in microbial community composition with up to 34 out of 162 taxa differing significantly in abundance between sampling groups. This large-scale microbial survey suggests that the shell microbial diversity of apparently healthy lobsters is influenced by spatial and temporal factors such as geographic location, as well as the length of time the carapace is exposed to the surrounding seawater.

Impacts of preweaning colostrum feeding practices and health measures on dairy cow production, while accounting for genetic potential.

Calf management and health are essential for setting up the foundation of a productive cow. The objectives of this study were to estimate the impact of preweaning practices on milk production parameters while accounting for an animal's genetic potential in New Brunswick, Canada. A retrospective cohort study was performed on 220 heifer calves from eight herds born in 2014-2015. Preweaning practices and health data were recorded by producers and reviewed by the herd veterinarian for each calf. The herd veterinarian also visited the farms to collect serum samples from calves and frozen colostrum samples. The production outcomes assessed were milk, protein and fat yields, standardized to 305 d for the first lactation (L1) and a combined group of lactations two and three (L2 + 3). The genomic potential was determined as genomic parent averages (GPA) for the associated production parameters. Analysis was performed with multivariable linear (L1) and linear mixed (L2 + 3) regression models. In L1, for every 1.0 kg increase in weaning weight, milk, protein, and fat yield increased by 25.5, 0.82, and 1.01 kg, respectively (P < 0.006). Colostrum feeding time (CFT) positively impacted L1 milk and protein production, with feeding between 1-2 h of life producing the greatest estimates of 626 kg of milk and 18.2 kg of protein yield (P < 0.007), compared to earlier or later CFT. Fat yield production was decreased by 80.5 kg (P < 0.006) in L1 when evaluating animals that developed a preweaning disease and were not treated with antibiotics compared to healthy untreated animals. Impacts on L2 + 3 were similar across all production outcomes, with a positive interaction effect of CFT and weaning weight. Compared to CFT < 1 h, the later CFT groups of 1-2 h and > 2 h produced greater yield outcomes of 68.2 to 72.6 kg for milk (P < 0.006), 2.06 to 2.15 kg for protein (P < 0.005), and 1.8 to 1.9 kg for fat (P < 0.045) for every 1 kg increase of weaning weight, respectively. The fit of all models was significantly improved with the inclusion of GPA. These results indicate that colostrum management and preweaning health measures impacted production parameters as adults. The inclusion of GPA significantly improved the accuracy of the models, indicating that this can be an important parameter to include in future studies.

The impact of calf management and health events have been predominately investigated during the preweaning period. However, calfhood events could also impact the animal's health and productivity as an adult. Results from this study indicate that colostrum feeding time and weaning weight were associated with production outcomes (milk, protein, and fat yields) across the first three lactations, and disease and antibiotic treatment can be detrimental to fat yield in the first lactation. By including genetic potential in the assessment of preweaning colostrum practices and health measures on production outcomes, we can more precisely identify areas to optimize calf management.

Herd-level relationship between antimicrobial use and presence or absence of antimicrobial resistance in gram-negative bovine mastitis pathogens on Canadian dairy farms.

Concurrent data on antimicrobial use (AMU) and resistance are needed to contain antimicrobial resistance (AMR) in bacteria. The present study examined a herd-level association between AMU and AMR in Escherichia coli (n=394) and Klebsiella species (n=139) isolated from bovine intramammary infections and mastitis cases on 89 dairy farms in 4 regions of Canada [Alberta, Ontario, Québec, and Maritime Provinces (Prince Edward Island, Nova Scotia, and New Brunswick)]. Antimicrobial use data were collected using inventory of empty antimicrobial containers and antimicrobial drug use rate was calculated to quantify herd-level AMU. Minimum inhibitory concentrations (MIC) were determined using Sensititre National Antimicrobial Resistance Monitoring System (NARMS) gram-negative MIC plate (Trek Diagnostic Systems Inc., Cleveland, OH). Isolates were classified as susceptible, intermediate, or resistant. Intermediate and resistant category isolates were combined to form an AMR category, and multivariable logistic regression models were built to determine herd-level odds of AMR to tetracycline, ampicillin, cefoxitin, chloramphenicol, trimethoprim-sulfamethoxazole combination, sulfisoxazole, streptomycin and kanamycin in E. coli isolates. In the case of Klebsiella species isolates, logistic regression models were built for tetracycline and sulfisoxazole; however, no associations between AMU and AMR in Klebsiella species were observed. Ampicillin-intermediate or -resistant E. coli isolates were associated with herds that used intramammarily administered cloxacillin, penicillin-novobiocin combination, and cephapirin used for dry cow therapy [odds ratios (OR)=26, 32, and 189, respectively], and intramammary ceftiofur administered for lactating cow therapy and systemically administered penicillin (OR=162 and 2.7, respectively). Use of systemically administered penicillin on a dairy farm was associated with tetracycline and streptomycin-intermediate or -resistant E. coli isolates (OR=5.6 and 2.8, respectively). Use of cephapirin and cloxacillin administered intramammarily for dry cow therapy was associated with increasing odds of having at least 1 kanamycin-intermediate or -resistant E. coli isolate at a farm (OR=8.7 and 9.3, respectively). Use of systemically administered tetracycline and ceftiofur was associated with cefoxitin-intermediate or -resistant E. coli (OR=0.13 and 0.16, respectively); however, the odds of a dairy herd having at least 1 cefoxitin-intermediate or -resistant E. coli isolate due to systemically administered ceftiofur increased with increasing average herd parity (OR=3.1). Association between herd-level AMU and AMR in bovine mastitis coliforms was observed for certain antimicrobials. Differences in AMR between different barn types and geographical regions were not observed.