Prevalence and Risk Factors Associated With Antimicrobial Resistance in Bacteria Related to Bovine Respiratory Disease-A Broad Cross-Sectional Study of Beef Cattle at Entry Into Canadian Feedlots.

A broad, cross-sectional study of beef cattle at entry into Canadian feedlots investigated the prevalence and epidemiology of antimicrobial resistance (AMR) in Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis, bacterial members of the bovine respiratory disease (BRD) complex. Upon feedlot arrival and before antimicrobials were administered at the feedlot, deep nasopharyngeal swabs were collected from 2,824 feedlot cattle in southern and central Alberta, Canada. Data on the date of feedlot arrival, cattle type (beef, dairy), sex (heifer, bull, steer), weight (kg), age class (calf, yearling), source (ranch direct, auction barn, backgrounding operations), risk of developing BRD (high, low), and weather conditions at arrival (temperature, precipitation, and estimated wind speed) were obtained. Mannheimia haemolytica, P. multocida, and H. somni isolates with multidrug-resistant (MDR) profiles associated with the presence of integrative and conjugative elements were isolated more often from dairy-type than from beef-type cattle. Our results showed that beef-type cattle from backgrounding operations presented higher odds of AMR bacteria as compared to auction-derived calves. Oxytetracycline resistance was the most frequently observed resistance across all Pasteurellaceae species and cattle types. Mycoplasma bovis exhibited high macrolide minimum inhibitory concentrations in both cattle types. Whether these MDR isolates establish and persist within the feedlot environment, requires further evaluation.

Risk factors of digital dermatitis in feedlot cattle.

Digital dermatitis (DD) has been reported in North American feedlots, although risk factors are not well characterized. Our objectives were to analyze: (1) foot and leg conformation and (2) pen hygiene, as potential variables that predispose feedlot cattle to DD. Production parameters in DD-affected cattle were compared with healthy cattle and with those diagnosed with more commonly known infectious lesion foot rot (FR). In total, 2,854 feedlot cattle in 11 pens in 2 feedlots were assessed (bi-weekly pen walks) throughout the feeding cycle. Pen condition was categorized as: "dry," "mud present but has good bedding," "more mud than bedding," and "excessive mud." Gait scoring was competed and cattle with abnormal gait or evident foot lesions (i.e., DD or FR) were restrained in a cattle chute for a close foot inspection (n=280), including scoring of foot angle and claw set and hind and side views of rear feet and legs. Cumulative incidence of DD (present or absent) and FR was 2.5% (71/2,854) and 11.6% (331/2,854), respectively. Foot and leg conformation was not significantly different between left and right sides or between cattle with (n=71) and without DD (n=209). Lameness was diagnosed in only 22% of cattle with DD. Cattle with DD gained 0.27 kg/d less compared with healthy cattle (mean ± SD: 1.29 ± 0.29 vs. 1.56 ± 0.27, P<0.05) and 0.4 kg/d less compared with FR (1.29 ± 0.29 vs. 1.69 ± 0.25). Presence of DD was not significantly different between pens with "dry" and "mud present but has good bedding," but for pens with "more mud than bedding" or "excessive mud," the risk of cattle having DD cases increased significantly [odds ratio (OR)=8.55, confidence interval (CI): 4.0-18.4 and OR=14.1, CI: 5.9-33.8, respectively]. In conclusion, it is important to keep good pen conditions to reduce the risk of DD, which can be managed through proper stocking density and strategic bedding, irrespective of foot and leg conformation.

Economic impact of digital dermatitis, foot rot, and bovine respiratory disease in feedlot cattle.

Digital dermatitis (DD) has emerged in North American feedlots, although production and economic impacts are not fully understood. Objectives of this study were to: (1) estimate the economic impact of a single case of DD, foot rot (FR), and bovine respiratory disease (BRD) in feedlot cattle and (2) determine its impact on average daily gain (ADG). Feedlot cattle health and production records were available from two feedlots for a 3-yr interval. The dataset consisted of 77,115 animal records, with 19.3% (14,900) diagnosed with a disease. Diseased animals were categorized into five groups: DD, FR, BRD, other diseases (OT), and two or more diseases (TM), with a treatment cumulative incidence of 6.0%, 59.1%, 10.7%, 12.7%, and 11.5%, respectively. FR was the disease with the highest cumulative incidence in both heifers and steers (58.8% and 59.6%, respectively). Of all fall-placed cattle diagnosed with any disease, 48.1% of the cases were FR. DD affected the partial budget in five out of the eight groups of cattle, with the highest impact of DD seen in grass yearling heifers and grass yearling steers: $-98 and $-96 CAD, respectively, relative to their healthier counterparts. Healthy cattle had a significantly higher ADG when compared with DD cattle in five of the eight categories, ranging from 0.11 kg/d in winter-placed heifers to 0.17 kg/d in fall-placed steers. In the economic analysis, it was concluded that on an individual animal basis, BRD was the most impactful of all analyzed diseases, whereas DD was second, marking the importance of controlling and mitigating this foot condition. Identifying differential effects of diseases on a partial budget analysis and ADG of the types of cattle stratified by sex enables feedlot producers to focus control and mitigation strategies on specific groups.

Prevalence and lameness-associated risk factors in Alberta feedlot cattle.

Lameness in cattle is a health and welfare concern; however, limited information is available on risk factors and the relationship between lameness and common diseases like bovine respiratory disease (BRD). Therefore, the objectives of this study were to: 1) identify prevalence of lameness in feedlot cattle and related risk factors of cattle diagnosed as lame; and 2) determine associations between BRD occurrence and lameness. Feedlot cattle health records were available from 28 feedlots for 10 yr. The data set consisted of 663,838 cattle records, with 13.9% (92,156) diagnosed with a disease, including 32.3%, 46.0%, and 22.0% with lameness, BRD, and other diagnoses, respectively. Lameness was classified into four categories: foot rot (FR), joint infections (JI), lame with no visible swelling (LNVS), and injuries (INJ), with a prevalence of 74.5%, 16.1%, 6.1%, and 3.1%, respectively. Lameness was compared across cattle types (arrival date and weight) as well as age classification (calf vs. yearling), gender (steer vs. heifer), and season of placement in the feedlot (spring, summer, fall, and winter). Within the disease-diagnosed population, lameness represented 28.5% of treated fall-placed calves, 38.5% of winter-placed calves, and 40.8% of treated yearlings. Foot rot was the most common diagnosis with 74.5% of all lameness diagnoses, with winter- and fall-placed calves more likely to be diagnosed with FR compared to yearlings (OR: 1.19, 95% CI: 1.10-1.30 and OR: 1.46, 95% CI: 1.38-1.55, respectively). Joint infections were the second most common diagnosis (16.1%). Compared to yearlings, fall-placed calves had a higher odds (OR: 3.64, 95% CI: 3.12-4.24) for JI. Injuries and LNVS were the least common but again fall-placed calves had higher odds of this diagnosis compared to yearlings (OR: 2.26, 95% CI: 1.70-2.99 and OR: 9.10, 95% CI: 6.26-13.2, respectively). Gender was significantly different for JI as steers were less likely affected compared to heifers (OR: 0.687, 95% CI: 0.545-0.867), and more likely affected by LNVS (OR: 2.46, 95% CI: 1.57-3.84). Of all lameness-associated deaths, JI accounted for almost 50%. Finally, cattle diagnosed with BRD were subsequently more likely to be diagnosed with INJ, JI, or LNVS (P < 0.001 for all comparisons). In conclusion, animal type and gender were associated with type of lameness diagnoses, allowing feedlots to allocate resources to groups at highest risk and focus on early intervention strategies.

Effect of ruminal acidosis and short-term low feed intake on indicators of gastrointestinal barrier function in Holstein steers.

The objective of this study was to determine effect of ruminal acidosis (RA) and low feed intake [LFI] on the regional barrier function of the gastrointestinal tract. Twenty-one Holstein steers were fed for ad libitum intake for 5 d (control [CON]), fed at 25% of ad libitum intake for 5 d (LFI), or provided 2 d of ad libitum intake followed by 1-d of feed restriction (25% of ad libitum intake), 1 d where 30% of ad libitum dry matter intake (DMI) was provided as pelleted barley followed by the full allocation (RA) and fed for ad libitum intake the following day. Tissues and digesta from the rumen, omasum, duodenum, jejunum, ileum, cecum, proximal, and distal colon were collected. Permeability was assessed using the mucosal-to-serosal flux of inulin (JMS-inulin) and mannitol (JMS-mannitol). Digesta pH was 0.81, 0.63, and 0.42 pH units less for RA than CON in the rumen, cecum, and proximal colon; while, LFI had pH that was 0.47 and 0.36 pH units greater in the rumen and proximal colon compared to CON. Total ruminal short-chain fatty acid (SCFA) concentration were less for LFI (92 mM; P = 0.010) and RA (87 mM; P = 0.007) than CON (172 mM) steers. In the proximal colon, the proportion of butyrate (P = 0.025 and P = 0.022) and isobutyrate (P = 0.019 and P = 0.019) were greater, and acetate (P = 0.028 and P = 0.028) was less for LFI and RA, respectively, when compared to CON steers. Ruminal papillae length, width, perimeter, and surface area were 1.21 mm, 0.78 mm, 3.84 mm, and 11.15 mm2 less for LFI than CON; while, RA decreased papillae width by 0.52 mm relative to CON. The JMS-mannitol was less for LFI steers than CON in the proximal colon (P = 0.041) and in the distal colon (P = 0.015). Increased gene expression for claudin 1, occludin, tight-cell junction protein 1 and 2, and toll-like receptor 4 were detected for LFI relative to CON in the rumen, jejunum, and proximal colon. For RA steers, expression of toll-like receptor 4 in the rumen, and occludin and tight-cell junction protein 1 were greater in the jejunum than CON. An acute RA challenge decreased pH in the rumen and large intestine but did not increase tissue permeability due to increases in the expression of genes related to barrier function within 1 d of the challenge. Steers exposed to LFI for 5 d had reduced ruminal SCFA concentrations, smaller ruminal papillae dimensions, and increased tissue permeability in the proximal and distal colon despite increases for genes related to barrier function and immune function.

In silico identification and high throughput screening of antigenic proteins as candidates for a Mannheimia haemolytica vaccine.

This study examined the use of comparative genomic analysis for vaccine design against Mannheimia haemolytica, a respiratory pathogen of ruminants. A total of 2,341genes were identified in at least half of the 23 genomes. Of these, a total of 240 were identified to code for N-terminal signal peptides with diverse sub-cellular localizations (78 periplasmic, 52 outer membrane, 15 extracellular, 13 cytoplasmic membrane and 82 unknown) and were examined in an ELISA assay using a coupled-cell free transcription/translation system for protein expressionwith antisera from cattle challenged with serovars 1, 2 or 6 of M. haemolytica. In total, 186 proteins were immunoreactive to at least one sera type and of these, 105 were immunoreactive to all sera screened. The top ten antigens based on immunoreactivity were serine protease Ssa-1 (AC570_10970), an ABC dipeptid transporter substrate-binding protein (AC570_04010), a ribonucleotide reductase (AC570_10780), competence protein ComE (AC570_11510), a filamentous hemagglutinin (AC570_01600), a molybdenum ABC transporter solute-binding protein (AC570_10275), a conserved hypothetical protein (AC570_07570), a porin protein (AC569_05045), an outer membrane assembly protein YeaT (AC570_03060), and an ABC transporter maltose binding protein MalE (AC570_00140). The framework generated from this research can be further applied towards rapid vaccine design against other pathogens involved in complex respiratory infections in cattle.

Reduced activities of thiamine-dependent and cytochrome c oxidase enzymes in cerebral cortex of cattle affected by sulfur-induced polioencephalomalacia.

Sulfur-induced polioencephalomalacia (PEM) is an important disease affecting cattle in certain geographical regions. However, the pathogenesis of brain damage is not completely understood. We previously observed that excess dietary sulfur may influence thiamine status and altered thiamine metabolism may be involved in the pathogenesis of sulfur-induced PEM in cattle. In this study, we evaluated the activities of thiamine-dependent enzymes [α-ketogluterate dehydrogenase (α-KGDH) and pyruvate dehydrogenase (PDH)] and cytochrome c oxidase (COX) in the cerebral cortex of sulfur-induced PEM-affected cattle (n = 9) and clinically normal cattle (n = 8, each group) exposed to low or high dietary sulfur [LS = 0.30% versus HS = 0.67% sulfur on a dry matter (DM) basis]. Enzyme activities in PEM brains were measured from the brain tissue regions and examined using ultraviolent (UV) light illumination to show fluorescence or non-fluorescence regions. No gross changes under regular or UV light, or histopathological changes indicative of PEM were detected in the brains of cattle exposed to LS or HS diets. The PDH, α-KGDH, and COX activities did not differ between LS and HS brains, but all enzymes showed significantly lower (P < 0.05) activities in UV-positive region of PEM brains compared with LS and HS brains. The UV-negative regions of PEM brain had similar PDH activities to LS and HS brains, but the activities of α-KGDH and COX were significantly lower than in LS and HS brains. The results of this study suggest that reduced enzyme activities of brain PHD, α-KGDH, and COX are associated with the pathogenesis of sulfur-induced PEM.

La polio-encéphalomalacie (PEM) induite par le souffre est une maladie importante affectant les bovins dans certaines régions géographiques. Toutefois, la pathogenèse des dommages cérébraux n'est pas complètement comprise. Nous avons observé antérieurement qu'un excès de souffre alimentaire peu influencer le statut de la thiamine et le métabolisme altéré de la thiamine pourrait être impliqué dans la pathogenèse de la PEM induite par le souffre chez les bovins. Dans la présente étude nous avons évalué les activités d'enzymes dépendant de la thiamine [α-kétoglutarate déshydrogénase (α-KGDH) et pyruvate déshydrogénase (PDH)] et du cytochrome c oxydase (COX) dans le cortex cérébral de bovins affectés de PEM induite par le souffre (n = 9) et de bovins cliniquement normaux (n = 8, chaque groupe) exposés à des quantités faibles (LS) ou élevés (HS) de souffre alimentaire (LS = 0,30 % vs HS = 0,67 % souffre sur une base de matière sèche). L'activité enzymatique dans les cerveaux PEM était mesurée à partir de régions du tissu cérébral et examinée à l'aide d'une lampe à rayons ultraviolets (UV) pour montrer les régions fluorescentes et non-fluorescentes. Aucun changement macroscopique n'était apparent à l'examen sous éclairage régulier ou lumière UV, et aucun changement histopathologique indicateur de PEM ne fut détecté dans les cerveaux des bovins exposés à des diètes LS ou HS. L'activité de PDH, de α-KGDH, et de COX ne différait pas entre les cerveaux LS et HS, mais tous les enzymes montraient une activité significativement plus faible (P < 0,05) dans les régions positive aux UV dans les cerveaux PEM comparativement aux cerveaux LS et HS. Les régions UV négative des cerveaux PEM avaient des activités PDH similaires à celles des cerveaux LS et HS, mais les activités de α-KGDH et de COX étaient significativement plus faibles que dans les cerveaux LS et HS. Les résultats de cette étude suggèrent que la réduction d'activités de PDH, α-KGDH et de COX du cerveau est associée avec la pathogenèse de PEM induite par le souffre.(Traduit par Docteur Serge Messier).

Comparative Genomic Analysis of Mannheimia haemolytica from Bovine Sources.

Bovine respiratory disease is a common health problem in beef production. The primary bacterial agent involved, Mannheimia haemolytica, is a target for antimicrobial therapy and at risk for associated antimicrobial resistance development. The role of M. haemolytica in pathogenesis is linked to serotype with serotypes 1 (S1) and 6 (S6) isolated from pneumonic lesions and serotype 2 (S2) found in the upper respiratory tract of healthy animals. Here, we sequenced the genomes of 11 strains of M. haemolytica, representing all three serotypes and performed comparative genomics analysis to identify genetic features that may contribute to pathogenesis. Possible virulence associated genes were identified within 14 distinct prophage, including a periplasmic chaperone, a lipoprotein, peptidoglycan glycosyltransferase and a stress response protein. Prophage content ranged from 2-8 per genome, but was higher in S1 and S6 strains. A type I-C CRISPR-Cas system was identified in each strain with spacer diversity and organization conserved among serotypes. The majority of spacers occur in S1 and S6 strains and originate from phage suggesting that serotypes 1 and 6 may be more resistant to phage predation. However, two spacers complementary to the host chromosome targeting a UDP-N-acetylglucosamine 2-epimerase and a glycosyl transferases group 1 gene are present in S1 and S6 strains only indicating these serotypes may employ CRISPR-Cas to regulate gene expression to avoid host immune responses or enhance adhesion during infection. Integrative conjugative elements are present in nine of the eleven genomes. Three of these harbor extensive multi-drug resistance cassettes encoding resistance against the majority of drugs used to combat infection in beef cattle, including macrolides and tetracyclines used in human medicine. The findings here identify key features that are likely contributing to serotype related pathogenesis and specific targets for vaccine design intended to reduce the dependency on antibiotics to treat respiratory infection in cattle.

Comparison of radiography and computed tomography for determining tracheal diameter and length in dogs.

OBJECTIVE: To compare radiographic and computed tomography (CT) measurements of tracheal size as would be made for the purpose of tracheal stent size selection. STUDY DESIGN: Cross-over. ANIMALS: Dogs (n = 15). METHODS: Canine cadavers without evidence of tracheal or respiratory disease were used for CT and digital radiography of the neck and thorax. Three observers each made 3 independent measurements at each of 5 tracheal locations, and also measured tracheal length, on each radiograph and for each CT scan on each cadaver. RESULTS: CT tracheal measurements were on average 1.03 mm larger (P < .01) compared with radiographic measurements for all 3 observers. CONCLUSIONS: Radiographic measurements of the canine trachea consistently underestimate tracheal size, and CT measurements are preferable for selecting tracheal stent size.

Occurrence of Incisional Complications After Closure of Equine Celiotomies With USP 7 Polydioxanone.

OBJECTIVES: To report the occurrence of, and risk factors associated with, incisional complications of equine ventral median celiotomies closed with USP 7 polydioxanone (7PD). STUDY DESIGN: Retrospective case series. SAMPLE POPULATION: Horses (n = 73; 75 celiotomies). METHODS: Medical records (2000-2010) were retrieved and reviewed for horses that had a ventral celiotomy closed with 7PD and survived ≥14 days. Follow-up (>1 year) was obtained from the medical record, owner, or referring veterinarian. Independent variables were selected based on risk factors identified in previous studies, perceived clinical relevance, and if there were adequate data recorded in the medical record. Statistical analysis, including multivariable logistic regression with a forward-building model process, was performed to evaluate variables associated with incisional complications. RESULTS: One or more incisional complication(s) occurred in 19 celiotomies (25.3%) during hospitalization or after discharge including: drainage (25.3%), infection (12.0%), and partial dehiscence (5.3%). Two of 63 horses (3.2%) available for follow-up developed an incisional hernia. Variables associated with incisional complications after multivariate analysis included: number of days hospitalized, surgery time, postoperative colic, and postoperative fever. CONCLUSION: Overall occurrence of incisional herniation after closure of ventral celiotomies with 7PD was low.

Ex vivo evaluation of 7 polydioxanone for closure of equine ventral midline celiotomies.

The objective of this study was to compare the bursting strength (BS) and mode of failure (MF) of ventral midline (VM) celiotomies closed with USP 7 polydioxanone (7PD) in 1 or 2 simple continuous sections. A bursting strength model, consisting of inserting and inflating a 200-L polyurethane bladder through a 25-cm VM celiotomy, was used on 15 fresh equine cadavers. Celiotomies were closed using 7PD in 2 separate sections (4 knots), 2 continuous sections (3 knots), or a single section (2 knots) using a simple continuous pattern. The horses' signalment, body weight, number of total knots, MF, and BS were recorded and analyzed statistically for interactions. No difference was found between the BS of VM celiotomies closure types (P = 0.4). All celiotomy/ suture constructs failed at the abdominal wall. The celiotomy closure types evaluated in this study provided a secure method of closure in VM celiotomies in vivo.

L'objectif de la présente étude était de comparer la force d'éclatement (BS) et le mode d'échec (MF) de laparotomies par la ligne ventrale médiale (VM) refermées avec du 7 polydioxanone USP (7PD) en une ou 2 sections continues. Un modèle de force d'éclatement, consistant en l'insertion et le gonflement une vessie de 200 L en polyuréthane via une laparotomie de 25 cm fut utilisé sur 15 cadavres frais de cheval. Les laparotomies étaient refermées en utilisant le 7PD en deux sections séparées (4 nœuds), 2 sections continues (3 nœuds), ou une section simple (2 nœuds) au moyen d'un patron simple continu. L'historique des chevaux, leur poids corporel, le nombre total de nœuds, MF, et BS ont été enregistrés et analysés statistiquement pour les interactions. Aucune différence ne fut trouvée entre les BS et les types de fermetures de VM des laparotomies (P = 0,4). Toutes les laparotomies/modes de suture ont lâché au niveau de la paroi abdominale. Les types de fermeture des laparotomies évalués dans ce projet ont fourni une méthode sécuritaire de fermeture par la VM de laparotomies in vivo.(Traduit par Docteur Serge Messier).

Characterization of Mannheimia haemolytica isolated from feedlot cattle that were healthy or treated for bovine respiratory disease.

Mannheimia haemolytica is the principal bacterial pathogen associated with bovine respiratory disease (BRD). As an opportunistic pathogen, M. haemolytica is also frequently isolated from the respiratory tract of healthy cattle. This study examined the characteristics of M. haemolytica collected using deep nasal swabs from healthy cattle (n = 49) and cattle diagnosed with BRD (n = 41). Isolates were analyzed by pulsed-field gel electrophoresis (PFGE), serotyped, and tested for antimicrobial susceptibility. Polymerase chain reaction (PCR) was used to screen isolates for virulence [leukotoxin C (lktC), putative adhesin (ahs), outer-membrane lipoprotein (gs60), O-sialoglycoprotease (gcp), transferring-binding protein B (tbpB) and UDP-N-acetyl-D-glucosamine-2-epimerase (nmaA)] and antimicrobial resistance [tet(H), bla ROB-1, erm(X), erm(42), msr(E)-mph(E) and aphA-1] genes. Isolates were genetically diverse but in three instances, M. haemolytica with the same pulsotype, resistance phenotype, and genotype were collected from cattle with BRD. This occurred once between cattle located in two different feedlots, once between cattle in the same feedlot, but in different pens, and once among cattle from the same feedlot in the same pen. Isolates from healthy cattle were primarily serotype 2 (75.5%) while those from individuals with BRD were serotype 1 (70.7%) or 6 (19.5%). Resistance to at least one antibiotic occurred more frequently (P < 0.001) in M. haemolytica collected from cattle with BRD (37%) compared with those that were healthy (2%). Overall, tetracycline resistance (18%) was the most prevalent resistant phenotype. All tetracycline-resistant M. haemolytica encoded tet(H). Ampicillin resistance (6%) and neomycin resistance (15%) were detected and corresponded to the presence of the bla ROB-1 and aphA-1 genes, respectively. Tilmicosin resistance (6%) was also detected, but the resistance genes responsible were not identified. The virulence genes lktC, ahs, gs60, and gcp were present in all isolates examined, while tbpB and nmaA were only detected in serotype 1 and serotype 6 isolates indicating they may be potential targets for serotype-specific identification or vaccine development. These results provide the first reported evidence of transmission and spread of antimicrobial-resistant M. haemolytica that have contributed to bovine respiratory disease in western Canadian feedlots.

Mannheimia haemolytica est la principale bactérie pathogène associée avec le complexe respiratoire bovin (BRD). En tant qu'agent pathogène opportuniste, M. haemolytica est également fréquemment isolée du tractus respiratoire de bovins en santé. Cette étude a permis d'examiner les caractéristiques des isolats de M. haemolytica obtenus lors d'écouvillonnage nasal profond de bovins en santé (n = 49) et de bovins diagnostiqués avec BRD (n = 41). Les isolats ont été analysés par électrophorèse en champs pulsés (PFGE), sérotypés, et testés pour leur sensibilité aux antibiotiques. Une réaction d'amplification en chaîne par la polymérase (PCR) a été utilisée pour cribler les isolats pour les gènes de virulence [leucotoxine C (lktC), adhésine putative (ahs), lipo-protéine de la membrane externe (gs60), O-sialoglycoprotéase (gcp), protéine liante de transfert B (tbpB) et l'UDP-N-acétyl-D-glucosamine-2-épimerase (nmaA)] et de résistance antimicrobienne [tet(H), blaROB-1, erm(X), erm(42), msr(E)-mph(E) et aphA-1]. Les isolats étaient génétiquement diversifiés mais à trois occasions, M. haemolytica avec le même pulsotype, phénotype de résistance, et génotype ont été obtenus de bovins avec BRD. Ceci s'est produit une fois entre des bovins situés dans deux parcs d'engraissement différents, une fois entre des bovins dans un même parc d'engraissement, mais dans des enclos différents, et une fois à partir de bovins dans le même parc d'engraissement et dans le même enclos. Les isolats obtenus des bovins en santé appartenaient principalement au sérotype 2 (75,5 %) alors que ceux provenant des animaux avec BRD étaient de sérotype 1 (70,7 %) ou 6 (19,5 %). De la résistance à au moins antibiotique a été notée plus fréquemment (P < 0,001) des isolats de M. haemolytica provenant des bovins avec BRD (37 %) comparativement à ceux obtenus des animaux en santé (2 %). De manière générale, la résistance à la tétracycline (18 %) était la plus fréquente. Tous les isolats de M. haemolytica résistants à la tétracycline étaient porteurs de tet(H). La résistance à l'ampicilline (6 %) et à la néomycine (15 %) a été détectée et correspondait respectivement à la présence des gènes blaROB-1 et aphA-1. De la résistance au tilmicosin (6 %) fut également détecté mais les gènes responsables de la résistance n'étaient pas identifiés. Les gènes de virulence lktC, ahs, gs60, et gcp étaient présents chez tous les isolats examinés, alors que les gènes tbpB et nmaA n'étaient détectés que chez les isolats des sérotypes 1 et 6 indiquant qu'ils pourraient être des cibles potentielles pour l'identification de sérotypes spécifiques ou le développement de vaccins. Ces résultats fournissent les premières évidences rapportées de transmission et de dissémination de M. haemolytica résistants aux antibiotiques qui ont contribué aux maladies respiratoires bovines dans les parcs d'engraissement de l'ouest canadien.(Traduit par Docteur Serge Messier).

Pathogens of bovine respiratory disease in North American feedlots conferring multidrug resistance via integrative conjugative elements.

In this study, we determined the prevalence of bovine respiratory disease (BRD)-associated viral and bacterial pathogens in cattle and characterized the genetic profiles, antimicrobial susceptibilities, and nature of antimicrobial resistance determinants in collected bacteria. Nasopharyngeal swab and lung tissue samples from 68 BRD mortalities in Alberta, Canada (n = 42), Texas (n = 6), and Nebraska (n = 20) were screened using PCR for bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus, bovine herpesvirus 1, parainfluenza type 3 virus, Mycoplasma bovis, Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni. Excepting bovine herpesvirus 1, all agents were detected. M. haemolytica (91%) and BVDV (69%) were the most prevalent, with cooccurrence in 63% of the cattle. Isolates of M. haemolytica (n = 55), P. multocida (n = 8), and H. somni (n = 10) from lungs were also collected. Among M. haemolytica isolates, a clonal subpopulation (n = 8) was obtained from a Nebraskan feedlot. All three bacterial pathogens exhibited a high rate of antimicrobial resistance, with 45% exhibiting resistance to three or more antimicrobials. M. haemolytica (n = 18), P. multocida (n = 3), and H. somni (n = 3) from Texas and Nebraska possessed integrative conjugative elements (ICE) that conferred resistance for up to seven different antimicrobial classes. ICE were shown to be transferred via conjugation from P. multocida to Escherichia coli and from M. haemolytica and H. somni to P. multocida. ICE-mediated multidrug-resistant profiles of bacterial BRD pathogens could be a major detriment to many of the therapeutic antimicrobial strategies currently used to control BRD.

Application of a new diagnostic approach to a bovine genital campylobacteriosis outbreak in a Saskatchewan beef herd.

A new real-time quantitative polymerase chain reaction (qPCR) test was used to diagnose Campylobacter fetus subsp. venerealis infection associated with dramatic reproductive losses in a commercial cow-calf herd. The results were verified with repeated culture, phenotypic characterization of the organism and DNA sequencing. This case demonstrates the need for a practical field test for C. fetus subsp. venerealis and the importance of considering this organism as a potential cause of pregnancy failure in beef herds.

Application d'une nouvelle approche diagnostique lors d'une éclosion de campylobactériose génitale bovine dans un troupeau bovin de la Saskatchewan. Un nouveau test quantitatif d'amplification en chaîne par la polymérase en temps réel (qACP) a été utilisé pour diagnostiquer une infection par Campylobacter fetus sous-espèce venerealis associée à une baisse spectaculaire de la reproduction dans un troupeau commercial de vaches-veaux. Les résultats ont été vérifiés à l'aide de cultures répétées, d'une caractérisation phénotypique de l'organisme et du séquençage de l'ADN. Ce cas démontre le besoin d'un test sur le terrain pratique pour C. fetus sous-espèce venerealis et l'importance de considérer cet organisme comme une cause potentielle d'échec de la gestation dans les troupeaux bovins.(Traduit par Isabelle Vallières).

Increase in average testis size of Canadian beef bulls.

Selection for adequate testis size in beef bulls is an important part of bull breeding soundness evaluation. Scrotal circumference (SC) is highly correlated with paired testis weight and is a practical method for estimating testis weight in the live animal. Most bulls presented for sale in Canada have SC included in the presale information. Scrotal circumference varies by age and breed, and may change over time due to selection for larger testis size. Therefore, it is important to periodically review the mean SC of various cattle breeds to provide valid bull selection criteria. Scrotal circumference data were obtained from bulls sold in western Canada from 2008 to 2011 and in Quebec from 2006 to 2010. Average scrotal circumferences for the most common beef breeds in Canada have increased significantly in the last 25 years. Differences between breeds have remained unchanged and Simmental bulls still have the largest SC at 1 year of age. Data provided here could aid in the establishment of new suggested minimum SC measurements for beef bulls.

Augmentation de la taille moyenne des testicules chez les taureaux de boucherie canadiens. La sélection de la taille adéquate des testicules chez les taureaux de boucherie représente une partie importante de l'évaluation de l'aptitude à l'utilisation comme reproducteur du taureau. La circonférence scrotale (CS) présente une corrélation élevée avec le poids des paires de testicules et est une méthode pratique d'estimer le poids des testicules chez l'animal vivant. La CS de la plupart des taureaux mis en vente au Canada est incluse dans les renseignements de prévente. La circonférence scrotale varie selon l'âge et la race et peut changer au fil du temps en raison de la sélection pour une taille supérieure de testicules. Par conséquent, il est important d'examiner périodiquement la CS moyenne des diverses races bovines afin de fournir des critères de sélection valides pour les taureaux. Les données sur la circonférence scrotale ont été obtenues de taureaux vendus dans l'Ouest canadien de 2008 à 2011 et au Québec de 2006 à 2010. Les circonférences scrotales moyennes pour les races bovines les plus communes ont augmenté significativement au cours des 25 dernières années. Les différences entre les races sont demeurées inchangées et les taureaux Simmental possèdent toujours la CS la plus grande à l'âge de 1 an. Les données fournies ici pourraient faciliter l'établissement de nouvelles mesures minimales suggérées pour la CS des taureaux de boucherie.(Traduit par Isabelle Vallières).

The use of lung biopsy to determine early lung pathology and its association with health and production outcomes in feedlot steers.

The objectives of this study were to determine if percutaneous lung biopsy can be used to characterize early pathologic changes in bovine lung associated with bovine respiratory disease (BRD), to determine if specific infectious respiratory pathogens can be identified in association with these changes, and to determine whether pulmonary pathology at arrival and at the time of initial diagnosis are associated with health and production outcomes. One hundred auction-market derived crossbred steer calves from a commercial feedlot in southern Alberta were included in this study. A percutaneous lung biopsy technique was used to obtain lung samples from the right middle lung. Steers were sampled 295 times yielding 283 samples with 210 (74%) containing lung tissue. Overall, histopathological changes were observed in 20 (9.5%) of lung biopsy samples. There were too few samples with pathology to reveal an association between lung pathology and subsequent health events. In general, percutaneous lung biopsy can be done safely on feedlot steers in a commercial feedlot setting with few clinical side effects. This technique did not prove useful as a diagnostic tool or prognostic indicator for early BRD. However, it may be useful for the diagnosis of BRD in targeted populations of commercial feedlot steers.

Les objectifs de la présente étude étaient de déterminer si une biopsie pulmonaire obtenue par voie transcutanée pouvait être utilisée afin de caractériser dans les poumons bovins les changements pathologiques hâtifs associés aux maladies respiratoires bovines (MRB), de déterminer si des agents infectieux pathogènes spécifiques au système respiratoire peuvent être identifiés en association avec ces changements, et de déterminer si les pathologies pulmonaires à l'arrivée et au moment du diagnostic initial sont associées avec les résultats de production et de santé. Cent bouvillons de race croisée issus d'encans et élevés dans un parc d'engraissement commercial du sud de l'Alberta ont été inclus dans cette étude. Une technique de biopsie pulmonaire transcutanée a été utilisée pour obtenir des échantillons de poumon du lobe pulmonaire médial droit. Les bouvillons ont été échantillonnés 295 fois produisant 283 échantillons avec 210 (74 %) contenant du tissu pulmonaire. Des changements histopathologiques ont été observés dans 20 (9,5 %) des échantillons de biopsie pulmonaire. Il y avait trop peu d'échantillons avec des pathologies pour démontrer une association entre une pathologie pulmonaire et des conséquences subséquentes sur la santé. En général, la biopsie pulmonaire transcutanée peut être faite de manière sécuritaire sur des bouvillons d'embouche en parc d'engraissement commercial avec peu d'effets cliniques secondaires. Cette technique ne s'est pas avérée utile comme outil diagnostique ou indicateur de pronostic pour les MRB hâtives. Toutefois, elle pourrait être utile pour le diagnostic de MRB dans des populations ciblées de bouvillons d'embouche en parc d'engraissement.(Traduit par Docteur Serge Messier).

Draft Genome Sequence of a Mannheimia haemolytica Serotype 6 Isolate Collected from the Nasopharynx of a Beef Calf with Bovine Respiratory Disease.

The draft genome of a Mannheimia haemolytica serotype 6 isolate obtained from the nasopharynx of a feedlot calf with bovine respiratory disease is described.

Assessing the inactivation of Mycobacterium avium subsp. paratuberculosis during composting of livestock carcasses.

Mycobacterium avium subsp. paratuberculosis causes Johne's disease (JD) in ruminants, with substantial economic impacts on the cattle industry. Johne's disease is known for its long latency period, and difficulties in diagnosis are due to insensitivities of current detection methods. Eradication is challenging as M. avium subsp. paratuberculosis can survive for extended periods within the environment, resulting in new infections in naïve animals (W. Xu et al., J. Environ. Qual. 38:437-450, 2009). This study explored the use of a biosecure, static composting structure to inactivate M. avium subsp. paratuberculosis. Mycobacterium smegmatis was also assessed as a surrogate for M. avium subsp. paratuberculosis. Two structures were constructed to hold three cattle carcasses each. Naturally infected tissues and ground beef inoculated with laboratory-cultured M. avium subsp. paratuberculosis and M. smegmatis were placed in nylon and plastic bags to determine effects of temperature and compost environment on viability over 250 days. After removal, samples were cultured and growth of both organisms was assessed after 12 weeks. After 250 days, M. avium subsp. paratuberculosis was still detectable by PCR, while M. smegmatis was not detected after 67 days of composting. Furthermore, M. avium subsp. paratuberculosis remained viable in both implanted nylon and plastic bags over the composting period. As the compost never reached a homogenous thermophilic (55 to 65°C) state throughout each structure, an in vitro experiment was conducted to examine viability of M. avium subsp. paratuberculosis after exposure to 80°C for 90 days. Naturally infected lymph tissues were mixed with and without compost. After 90 days, M. avium subsp. paratuberculosis remained viable despite exposure to temperatures typically higher than that achieved in compost. In conclusion, it is unlikely composting can be used as a means of inactivating M. avium subsp. paratuberculosis associated with cattle mortalities.

Ex vivo comparison of 7 polydioxanone, 2 polyglactin 910 for closure of ventral median celiotomy in horses.

OBJECTIVE: To compare bursting strength and failure mode between ventral median celiotomies closed with USP 7 braided polydioxanone (7PD) or USP 2 polyglactin 910 (2PG). STUDY DESIGN: Ex vivo experimental. ANIMALS: Equine cadavers (n = 10). METHODS: A 25 cm ventral median celiotomy was created in fresh equine cadavers. A 200 L polyurethane bladder was inserted into the abdomen. Celiotomies were closed in a simple continuous pattern with 2 sections of 7PD or 2PG. The bladder was inflated with compressed air until construct failure. The horses' signalment, body weight, suture type, failure mode (suture or abdominal wall), and bursting strength (mmHg) were recorded. Interactions between independent and dependent variables were assessed with statistical tests including linear regression. RESULTS: Failure mode was significantly different by suture type (P = .01). Four of 5 celiotomies closed with 2PG failed at the suture; whereas, 0 celiotomies closed with 7PD failed at the suture. In celiotomies closed with 7PD, increasing age was highly and negatively correlated with bursting strength (r = -0.99). When the effect of age was controlled, 7PD had a significantly higher bursting strength than 2PG (P = .024). CONCLUSION: 7PD has a higher bursting strength compared with 2PG. Suture failure was the main failure mode for 2PG; whereas, all celiotomies closed with 7PD failed at the abdominal wall.

Ex vivo comparison of bursting strength of ventral median and right ventral paramedian celiotomies in horses.

OBJECTIVE: To compare bursting strength and failure mode between ventral median (VM) and right ventral paramedian (RVP) celiotomies closed with 1 section of USP 7 braided polydioxanone (7PD). STUDY DESIGN: Ex vivo experimental. ANIMALS: Equine cadavers (n = 12). METHODS: A 25 cm VM or RVP (positioned 5 cm lateral to the linea alba) celiotomy was created in fresh equine cadavers. A 200 L polyurethane bladder was inserted into the abdomen. Celiotomies were closed in a simple continuous pattern with 1 section of 7PD. The bladder was inflated with compressed air until construct failure. Horse signalment, body weight, celiotomy type, failure mode (suture or abdominal wall), failure location (adjacent or remote from the celiotomy), and bursting strength (mmHg) were recorded. Interactions between independent and dependent variables were assessed with statistical tests including linear regression. RESULTS: Increasing age (P = .002) and Quarter horse-type breed (P = .01) had a negative effect on bursting strength. When age and breed were controlled, RVP celiotomies had a lower bursting strength compared with VM celiotomies (P = .039). None of the celiotomies failed at the suture. CONCLUSION: VM celiotomies have a greater bursting strength than RVP celiotomies when age and breed are controlled. Celiotomy bursting strength decreases with increasing age and is lower in Quarter horse-type breeds compared with non-Quarter horse-type breeds.