Partial herd hoof trimming results in a higher economic net benefit than whole herd hoof trimming in dairy herds.

Sole ulcers, a common cause of lameness is the costliest non-infectious foot lesion in dairy cows and one of the most prevalent non-infectious foot lesions in freestall housing systems. Costs associated with sole ulcers are treatment costs, plus increased labor and decreased productivity and fertility. Routine hoof trimming is part of a strategy to manage sole ulcers. However, hoof trimming strategies differ among farms. The two most frequently applied strategies are: 1) partial herd hoof trimming with a 2-month interval between trims; and 2) whole herd hoof trimming at 6-month intervals. A Markov model was developed to investigate whether every 2 months partial herd hoof trimming or whole herd hoof trimming every 6 months was the most cost-effective strategy to avoid costs associated with sole ulcers. In this model, the net benefits for a 100-cow herd and the average productive life span of a dairy cow in intensive dairy systems of 3 years were evaluated. Partial herd hoof trimming was the most cost-effective strategy 100% of the time compared to whole herd hoof trimming, with a difference in 3-year net benefits of US$4,337 (95% CI: US$2,713-US$5,830). Based on sensitivity analyses, variables that were the sources of the biggest uncertainty in the model were herd size, the probability of being trimmed in a partial herd trim, and the prevalence of sole ulcers. To further investigate the impacts of herd size and of probability of being trimmed, various scenario analyses were conducted. With increasing herd size, the difference in net benefits in favor of partial herd hoof trimming increased even more. Scenario analyses about the probability of getting trimmed all indicated that targeted intervention increased the difference in net benefits in favor of partial herd hoof trimming. However, if the selection of cows to be trimmed in a partial herd trim was random, the whole herd hoof trimming strategy became cost-effective. Therefore, targeted selection and early intervention are necessary to decrease costs associated with sole ulcers.

Removing bovine leukemia virus infected animals with high proviral load leads to lowering within-herd prevalence and new case reduction.

Bovine leukosis is prevalent in the North American dairy industry and its effect on animal health and production is widely documented. However, not all bovine leukemia virus (BLV) infected animals transmit the virus equally. Animals with high BLV proviral loads (HPL) are associated with higher transmission risks and therefore, their removal may reduce transmission and eventually within-herd prevalence. We aimed to evaluate the impact of selectively removing HPL cows on the within-herd BLV prevalence and incidence rate of BLV infection in 10 dairy herds. Annual blood and/or milk samples were collected from adult cows over 3 years. Positivity with BLV were determined by ELISA tests and proviral loads in blood of BLV-positive animals were estimated with BLV SS1 quantitative PCR assays. Herd managers were encouraged to consider the proviral load when making culling decisions and implement BLV control practices. High proviral load cows had the highest relative risk of removal indicating the farmers prioritized HPL cows for culling. The within-herd BLV prevalence decreased significantly in 4 herds whereas BLV incidence rate decreased in 9 herds. Over the 3 years, the proviral load demonstrated a relatively stable level, suggesting a single proviral load test in an adult cow may suffice to make culling decisions.

Proinflammatory CD14highCD16low monocytes/macrophages prevail in Treponema phagedenis-associated bovine digital dermatitis.

Digital dermatitis (DD) is a skin disease in cattle characterized by painful inflammatory ulcerative lesions in the feet, mostly associated with local colonization by Treponema spp., including Treponema phagedenis. The reason why most DD lesions remain actively inflamed and progress to chronic conditions despite antibiotic treatment remains unknown. Herein, we show an abundant infiltration of proinflammatory (CD14highCD16low) monocytes/macrophages in active DD lesions, a skin response that was not mitigated by topical treatment with oxytetracycline. The associated bacterium, T. phagedenis, isolated from DD lesions in cattle, when injected subcutaneously into mice, induced abscesses with a local recruitment of Ly6G+ neutrophils and proinflammatory (Ly6ChighCCR2+) monocytes/macrophages, which appeared at infection onset (4 days post challenge) and persisted for at least 7 days post challenge. When exploring the ability of macrophages to regulate inflammation, we showed that bovine blood-derived macrophages challenged with live T. phagedenis or its structural components secreted IL-1ß via a mechanism dependent on the NLRP3 inflammasome. This study shows that proinflammatory characteristics of monocytes/macrophages and neutrophils dominate active non-healing ulcerative lesions in active DD, thus likely impeding wound healing after antibiotic treatment.

Effects of bovine leukemia virus seropositivity and proviral load on milk, fat, and protein production of dairy cows.

The objective was to evaluate the effects of bovine leukemia virus (BLV) infection, as determined by BLV seropositivity and proviral load, on 305-d milk, fat, and protein production of dairy cows. A cross-sectional study was conducted among 1,712 cows from 9 dairy herds in Alberta, Canada. The BLV status was assessed using an antibody ELISA, whereas BLV proviral load in BLV-seropositive cattle was determined with quantitative PCR. Dairy Herd Improvement 305-d milk, fat, and protein production data were obtained for all enrolled cattle. Differences in these milk end points were assessed in 2 ways: first, by categorizing cows based on BLV serostatus (i.e., BLV positive or negative), and second, by categorizing based on BLV proviral load (i.e., BLV negative, low proviral load [LPL] BLV positive, and high proviral load [HPL] BLV positive). A mixed-effect multivariable linear regression model was used to assess differences in milk parameters. We found that BLV positivity, adjusted for parity and natural log-transformed somatic cell count (SCC), was not associated with reduction in 305-d milk, fat, or protein production. However, significant reductions in 305-d milk, fat, and protein yield occurred in HPL cows, but not in LPL cows, compared with BLV-negative cows, when adjusted for parity number and natural log-transformed SCC. In summary, BLV proviral load may predict effects of BLV infection on milk, fat, and protein production.

Can intake data inform on impacts of repeated subsidized onsite spay-neuter clinics for dogs?

Objective: Subsidized dog care and population management programs (DPM) are often implemented for dog population control where for-profit veterinary care is inaccessible. However, impacts of such programs are rarely assessed. The goal of this project was to determine if and how previously collected intake data from ongoing high-volume spay-neuter clinics could be used to measure impacts of such DPM programs. Animals: We used intake data collected from 2008 to 2019 from spay-neuter clinics that had been delivered repeatedly over a 10-year period in 6 First Nations communities in Alberta, to assess changes in intake dog characteristics. Procedures: Numbers of dogs brought in for spay-neuter surgery or surrendered, and their ages, sexes, breeds, weights, and body condition scores were compared. Reasons for surrender were investigated and socioeconomic factors were investigated as possible drivers for community differences in clinic participation rates and clinic sex ratios. Results: Socioeconomic indicators did not differ between the 6 participating communities; however, the total number of clinics requested by communities varied. In early years, female dogs were more likely to be brought to the clinics to be spayed whereas, in later years, more males were seen. The age at which animals were brought in for spay or neuter decreased over time (P < 0.05) but the surrender age did not. Breed proportions of x-large, small, and x-small breeds varied over time for both spay-neuter and surrender dogs (P < 0.05), with large-breed dogs always being the most common. However, there was an increase in small and x-small breeds in the final years of the study. Finally, weight status, a calculated estimate of body condition of spay-neuter dogs, increased over time within large and medium breeds, whereas the body condition score of surrendered dogs shifted from "thin" to "ideal" over time. Conclusions and clinical relevance: This work highlights the potential and challenges of using intake data to assess impacts of spay-neuter clinics that occur repeatedly over many years in the same communities. Overall increased weight status, high participation rates, and reduction of age at intake suggest positive effects of the assessed spay-neuter programs.

Les données d'admission peuvent-elles renseigner sur les impacts des cliniques de stérilisation sur place pour les chiens répétées et subventionnées? Objectif: Des programmes subventionnés de soins canins et de gestion de la population (DPM) sont souvent mis en œuvre pour limiter la population canine là où les soins vétérinaires à but lucratif sont inaccessibles. Cependant, les impacts de ces programmes sont rarement évalués. L'objectif de ce projet était de déterminer si et comment les données d'admission précédemment collectées dans les cliniques de stérilisation à grand volume en cours pourraient être utilisées pour mesurer les impacts de tels programmes de DPM. Animaux: Nous avons utilisé les données d'admission recueillies de 2008 à 2019 dans des cliniques de stérilisation qui avaient été dispensées à plusieurs reprises sur une période de 10 ans dans 6 communautés des Premières Nations de l'Alberta, pour évaluer les changements dans les caractéristiques d'admission des chiens. Procédures: Le nombre de chiens amenés pour une chirurgie de stérilisation ou cédés, ainsi que leurs âges, sexes, races, poids et scores de condition physique ont été comparés. Les raisons de l'abandon ont été étudiées ainsi que les facteurs socio-économiques en tant que facteurs possibles des différences communautaires dans les taux de participation aux cliniques et les ratios des sexes entre les cliniques. Résultats: Les indicateurs socioéconomiques ne différaient pas entre les 6 communautés participantes; cependant, le nombre total de cliniques demandées par les communautés variait. Au cours des premières années, les chiennes étaient plus susceptibles d'être amenées aux cliniques pour être stérilisées, tandis que dans les années suivantes, davantage de mâles étaient vus. L'âge auquel les animaux ont été amenés pour la castration ou la stérilisation a diminué avec le temps (P < 0,05), mais pas l'âge d'abandon. Les proportions de races très grandes, petites et très petites variaient au fil du temps pour les chiens stérilisés et les chiens abandonnés (P < 0,05), les chiens de grande race étant toujours les plus courants. Cependant, il y a eu une augmentation des races petites et très petites au cours des dernières années de l'étude. Enfin, le statut pondéral, une estimation calculée de la condition corporelle des chiens stérilisés, a augmenté avec le temps au sein des races grandes et moyennes, tandis que le score de condition corporelle des chiens abandonnés est passé de « mince ¼ à « idéal ¼ au fil du temps. Conclusions et pertinence clinique: Ce travail met en évidence le potentiel et les défis liés à l'utilisation des données d'admission pour évaluer les impacts des cliniques de stérilisation qui se déroulent à plusieurs reprises sur de nombreuses années dans les mêmes communautés. L'augmentation globale du statut pondéral, les taux de participation élevés et la réduction de l'âge à l'admission suggèrent des effets positifs des programmes de stérilisation évalués.(Traduit par Dr Serge Messier).

Individual drivers and barriers to adoption of disease control and welfare practices in dairy and beef cattle production: a scoping review.

The implementation of disease control and welfare practices is an essential part of limiting disease exposure in livestock, however successful adoption of these practices seem to be low in both the beef and dairy cattle industries. The main objectives of this scoping review were to characterize literature published exploring beef and dairy cattle producers' perceptions on the implementation of various disease control and welfare practices, identify major themes of drivers and barriers that influence producers' adoption of these practices, and identify current gaps in knowledge. A total of 2,486 articles were obtained from two database literature searches and screened, from which 48 articles published between 2010 and 2021 were deemed eligible and charted. Europe was the most common region for articles (58%). A majority of articles focused solely on dairy producers (52%). A wide range of barriers and drivers which were categorized into 4 and 5 key themes, respectively. The most commonly mentioned driver was animal health, welfare, and safety, while the most common barrier was costs. Potential gaps in literature were identified, including the underrepresentation of beef producer perceptions relative to dairy producers in current literature.

Impacts of commingling preconditioned and auction-derived beef calves on bovine respiratory disease related morbidity, mortality, and weight gain.

Introduction: Stressors predisposing to bovine respiratory disease (BRD) upon arrival in the feedlot, include the ranch to feedlot transition and mixing cattle from multiple sources. Preconditioning (PC) reduces multiple stressors, but commingling PC and auction-derived (AD) calves in a feedlot may increase BRD risk. Our objective was to evaluate PC calf performance over the first 40 days in the feedlot and determine impacts of commingling with varying proportions of AD calves (25, 50, and 75%). Methods: Calves were either preconditioned at one ranch (n = 250) or mixed-source and bought from a local auction (n = 250). At arrival, calves were assigned into 1 of 5 pens: 100 PC, 75 PC, 50 PC, 25 PC, and 0 PC, reflecting the percentage of PC calves in a 100-head pen. Results: Over 40 days, morbidity in pen 100 PC was lower compared to 0 PC (24 vs. 50%, P < 0.001) and varied in commingled pens, being highest (63%) in 25 PC and least (21%) in 50 PC (P < 0.05). There were 3 AD deaths in 0 PC and 2 deaths in 25 PC. The AD calves in 0 PC were 3 times more likely to get BRD than PC calves in 100 PC; however, AD calves gained 0.49 kg/d more than PC calves (P < 0.0001). Ignoring pen placement, AD calves were 2.76 times more likely to get BRD but gained 0.27 kg/d more than PC calves (P < 0.0001). Commingling did not affect morbidity of PC (P = 0.5) or AD calves (P = 0.96), implying commingling did not affect health. Calves in 25 PC were 3.39 times more likely to get BRD than those in the 100 PC (P < 0.001). Furthermore, 25 PC calves gained the most (1.08 kg/d), followed by 50 PC (0.62 kg/d) and 75 PC (0.61 kg/d), compared to 100 PC (P < 0.05). Calf weight at arrival modified ADG (P < 0.05). Discussion: In conclusion, PC calves had lower morbidity over the first 40 days, irrespective of commingling. With larger variations in arrival weight, there was no advantage of PC for ADG in the first 40 days. The unknown weaning strategies and comparable arrival weights of AD calves may have contributed to greater ADG in AD calves.

Invited review: Selective treatment of clinical mastitis in dairy cattle.

Treatment of clinical mastitis (CM) and use of antimicrobials for dry cow therapy are responsible for the majority of animal-defined daily doses of antimicrobial use (AMU) on dairy farms. However, advancements made in the last decade have enabled excluding nonsevere CM cases from antimicrobial treatment that have a high probability of cure without antimicrobials (no bacterial causes or gram-negative, excluding Klebsiella spp.) and cases with a low bacteriological cure rate (chronic cases). These advancements include availability of rapid diagnostic tests and improved udder health management practices, which reduced the incidence and infection pressure of contagious CM pathogens. This review informed an evidence-based protocol for selective CM treatment decisions based on a combination of rapid diagnostic test results, review of somatic cell count and CM records, and elucidated consequences in terms of udder health, AMU, and farm economics. Relatively fast identification of the causative agent is the most important factor in selective CM treatment protocols. Many reported studies did not indicate detrimental udder health consequences (e.g., reduced clinical or bacteriological cures, increased somatic cell count, increased culling rate, or increased recurrence of CM later in lactation) after initiating selective CM treatment protocols using on-farm testing. The magnitude of AMU reduction following a selective CM treatment protocol implementation depended on the causal pathogen distribution and protocol characteristics. Uptake of selective treatment of nonsevere CM cases differs across regions and is dependent on management systems and adoption of udder health programs. No economic losses or animal welfare issues are expected when adopting a selective versus blanket CM treatment protocol. Therefore, selective CM treatment of nonsevere cases can be a practical tool to aid AMU reduction on dairy farms.

Life history matters: Differential effects of abomasal parasites on caribou fitness.

Parasites can impact wildlife populations through their effects on host fitness and survival. The life history strategies of a parasite species can dictate the mechanisms and timing through which it influences the host. However, unravelling this species-specific effect is difficult as parasites generally occur as part of a broader community of co-infecting parasites. Here, we use a unique study system to explore how life histories of different abomasal nematode species may influence host fitness. We examined abomasal nematodes in two adjacent, but isolated, West Greenland caribou (Rangifer tarandus groenlandicus) populations. One herd of caribou were naturally infected with Ostertagia gruehneri, a common and dominant summer nematode of Rangifer sspp., and the other with Marshallagia marshalli (abundant; winter) and Teladorsagia boreoarcticus (less abundant; summer), allowing us to determine if these nematode species have differing effects on host fitness. Using a Partial Least Squares Path Modelling approach, we found that in the caribou infected with O. gruehneri, higher infection intensity was associated with lower body condition, and that animals with lower body condition were less likely to be pregnant. In caribou infected with M. marshalli and T. boreoarcticus, we found that only M. marshalli infection intensity was negatively related to body condition and pregnancy, but that caribou with a calf at heel were more likely to have higher infection intensities of both nematode species. The differing effects of abomasal nematode species on caribou health outcomes in these herds may be due to parasite species-specific seasonal patterns which influence both transmission dynamics and when the parasites have the greatest impact on host condition. These results highlight the importance of considering parasite life history when testing associations between parasitic infection and host fitness.

Broad-spectrum infrared thermography for detection of M2 digital dermatitis lesions on hind feet of standing dairy cattle.

Low-effort, reliable diagnostics of digital dermatitis (DD) are needed, especially for lesions warranting treatment, regardless of milking system or hygienic condition of the feet. The primary aim of this study was to test the association of infrared thermography (IRT) from unwashed hind feet with painful M2 lesions under farm conditions, with lesion detection as ultimate goal. Secondary objectives were to determine the association between IRT from washed feet and M2 lesions, and between IRT from unwashed and washed feet and the presence of any DD lesion. A total of 641 hind feet were given an M-score and IRT images of the plantar pastern were captured. Multivariable logistic regression analyses were done with DD status as dependent variable and maximum infrared temperature (IRTmax), lower leg cleanliness score and locomotion score as independent variables, and farm as fixed effect. To further our understanding of IRTmax within DD status, we divided IRTmax into two groups over the median value of IRTmax in the datasets of unwashed and washed feet, respectively, and repeated the multivariable logistic regression analyses. Higher IRTmax from unwashed hind feet were associated with M2 lesions or DD lesions, in comparison with feet without an M2 lesion or without DD, adjusted odds ratio 1.6 (95% CI 1.2-2.2) and 1.1 (95% CI 1.1-1.2), respectively. Washing of the feet resulted in similar associations. Dichotomization of IRTmax substantially enlarged the 95% CI for the association with feet with M2 lesions indicating that the association becomes less reliable. This makes it unlikely that IRTmax alone can be used for automated detection of feet with an M2 lesion. However, IRTmax can have a role in identifying feet at-risk for compromised foot health that need further examination, and could therefore function as a tool aiding in the automated monitoring of foot health on dairy herds.

Selective treatment of nonsevere clinical mastitis does not adversely affect cure, somatic cell count, milk yield, recurrence, or culling: A systematic review and meta-analysis.

Treatment of clinical mastitis (CM) contributes to antimicrobial use on dairy farms. Selective treatment of CM based on bacterial diagnosis can reduce antimicrobial use, as not all cases of CM will benefit from antimicrobial treatment, e.g., mild and moderate gram-negative infections. However, impacts of selective CM treatment on udder health and culling are not fully understood. A systematic search identified 13 studies that compared selective versus blanket CM treatment protocols. Reported outcomes were synthesized with random-effects models and presented as risk ratios or mean differences. Selective CM treatment protocol was not inferior to blanket CM treatment protocol for the outcome bacteriological cure. Noninferiority margins could not be established for the outcomes clinical cure, new intramammary infection, somatic cell count, milk yield, recurrence, or culling. However, no differences were detected between selective and blanket CM treatment protocols using traditional analyses, apart from a not clinically relevant increase in interval from treatment to clinical cure (0.4 d) in the selective group and higher proportion of clinical cure at 14 d in the selective group. The latter occurred in studies co-administering nonsteroidal anti-inflammatories only in the selective group. Bias could not be ruled out in most studies due to suboptimal randomization, although this would likely only affect subjective outcomes such as clinical cure. Hence, findings were supported by a high or moderate certainty of evidence for all outcome measures except clinical cure. In conclusion, this review supported the assertion that a selective CM treatment protocol can be adopted without adversely influencing bacteriological and clinical cure, somatic cell count, milk yield, and incidence of recurrence or culling.

Underlying genetic architecture of resistance to mastitis in dairy cattle: A systematic review and gene prioritization analysis of genome-wide association studies.

Mastitis, the most frequent disease in dairy cattle. Resistance to mastitis is a complex, polygenic trait controlled by several genes, each with small effects. Genome-wide association studies have been widely used to identify genomic variants associated with complex traits, including resistance to mastitis, to elucidate the underlying genetic architecture of the trait. However, no systematic review and gene prioritization analysis have been conducted to date on GWAS results for resistance to mastitis in dairy cattle. Hence, the objective was to perform a systematic review and gene prioritization analysis of GWAS studies to identify potential functional candidate genes associated with resistance to mastitis-related traits in dairy cattle. Four electronic databases were searched from inception to December 2020, supplemented with multiple sources of gray literature, to identify eligible articles. Annotation for genes and quantitative trait loci (QTL), and QTL enrichment analysis were conducted using GALLO. Gene prioritization analysis was performed by a guilty-by-association approach using GUILDify and ToppGene. From 52 articles included within this systematic review, 30 articles were used for further functional analyses. Gene and QTL annotation resulted in 9,125 and 43,646 unique genes and QTL, respectively, from 39 studies. In general, overlapping of genes across studies was very low (mean ± SD = 0.02% ± 0.07%). Most annotated genes were associated with somatic cell count-related traits and the Holstein breed. Within all annotated genes, 74 genes were shared among Holstein, Jersey, and Ayrshire breeds. Approximately 7.5% of annotated QTL were related to QTL class "health." Within the health QTL class, 2.6 and 2.2% of QTL were associated with clinical mastitis and somatic cell count-related traits. Enrichment analysis of QTL demonstrated that many enriched QTL were associated with somatic cell score located in Bos taurus autosomes 5, 6, 16, and 20. The prioritization analysis resulted in 427 significant genes after multiple test correction (false discovery rate of 5%) from 26 studies. Most prioritized genes were located in Bos taurus autosomes 19 and 7, and most top-ranked genes were from the cytokine superfamily (e.g., chemokines, interleukins, transforming growth factors, and tumor necrosis factor genes). Although most prioritized genes (397) were associated with somatic cell count-related traits, only 54 genes were associated with clinical mastitis-related traits. Twenty-four genes (ABCC9, ACHE, ADCYAP1, ARC, BCL2L1, CDKN1A, EPO, GABBR2, GDNF, GNRHR, IKBKE, JAG1, KCNJ8, KCNQ1, LIFR, MC3R, MYOZ3, NFKB1, OSMR, PPP3CA, PRLR, SHARPIN, SLC1A3, and TNFRSF25) were reported for both somatic cell count and clinical mastitis-related traits. Prioritized genes were mainly associated with immune response, regulation of secretion, locomotion, cell proliferation, and development. In conclusion, this study provided a fine-mapping of previously identified genomic regions associated with resistance to mastitis and identified key functional candidate genes for resistance to mastitis, which can be used to develop enhanced genomic strategies to combat mastitis by increasing mastitis resistance through genetic selection.

Impact of digital dermatitis on locomotion and gait traits of beef cattle.

Digital dermatitis (DD) is an infectious skin disease and a major cause of lameness that significantly impacts cattle productivity and welfare. However, DD does not always result in lameness and lameness scoring systems are not specific to hoof pathologies. Digital dermatitis detection protocols could be improved by including gait traits most related to DD. The aims of this study were to 1) determine the association between DD M-stage ("M" for Mortellaro), locomotion, and gait traits: arched back (AB), asymmetric gait (AG), head bobbing (HB), tracking up (TU), and reluctance to bear weight (WB), and 2) determine which traits are most associated with DD. Cattle (n = 480) from three feedlots were enrolled. Locomotion score (LS) and gait traits were assessed as cattle walked four strides along a dirt alleyway. Next, cattle were restrained in a chute, each hind foot lifted, and DD M-stage (absent, active, or chronic) determined. The association between presence of DD, LS, and gait traits were scored independently (n = 291). For both LS and gait the lowest score represents normal and the highest score severely altered. Digital dermatitis presence was associated with higher LS (P < 0.001). Odds ratios (ORs) for cattle with DD being lame or moderately to severely lame were 8.0 (P < 0.001) and 10.1 (P < 0.001) times more than cattle without lesions. Cattle with active lesions had the greatest odds of being lame (OR = 9.4; P < 0.001). Digital dermatitis presence was associated with all gait traits (P < 0.001), where AG (OR = 5.5; P < 0.001) and WB (OR = 5.8; P < 0.001) had the greatest OR for classifying cattle with DD as having altered gait. The OR for cattle with active lesions having altered gait was greatest for WB which was 6.0 (P < 0.001) times greater than cattle without lesions. The OR for cattle with chronic lesions having altered gait was greatest for AG being 6.5 (P < 0.001) times more than cattle without lesions. All gait traits had low sensitivity (Se) for detecting cattle with DD and varied from 6.7% to 55.8%. Locomotion score (Se 55.8%) and AG (Se 44.2%) were most predictive with positive predictive values of 76.6% and 74.3%, respectively. Specificity for all traits ranged from 94.1% for LS to 98.4% for WB with negative predictive values of 72.1% and 68.9%, respectively. In conclusion, LS, WB, and AG had the strongest association with cattle that had DD. Locomotion scoring that includes a focus on WB and AG is the best tool to detect DD in beef cattle.

Digital dermatitis (DD) impacts cattle health, productivity, and welfare; and is an emerging challenge for the beef industry. The most obvious clinical sign associated with DD is lameness; however, not all cattle afflicted with DD will become lame. Typically, locomotion scoring systems are used to assess lameness in cattle. These scoring systems are not specific for hoof pathologies, may not account for subtle changes in gait, and often reflect the needs of dairy cattle. Consequently, nonlame cattle with DD often go undiagnosed. By observing locomotion and other gait traits together we can identify gait traits that are most associated with DD in beef cattle and thereby develop targeted protocols for DD detection. Cattle with DD were consistently more associated with being lame compared to DD-free cattle. The two most important gait traits associated with cattle with DD were reluctance to bear weight (WB) and asymmetric gait (AG); however, their sensitivity to distinguish cattle with DD was low. These findings indicate that locomotion scoring that includes a focus on WB and AG is the best tool to detect DD in beef cattle.

Association of Environmental Factors with Seasonal Intensity of Erysipelothrix rhusiopathiae Seropositivity among Arctic Caribou.

Several caribou (Rangifer tarandus) populations have been declining concurrently with increases in infectious diseases in the Arctic. Erysipelothrix rhusiopathiae, a zoonotic bacterium, was first described in 2015 as a notable cause of illness and death among several Arctic wildlife species. We investigated epidemiologic and environmental factors associated with the seroprevalence of E. rhusiopathiae in the Arctic and found that seropositivity was highest during warmer months, peaking in September, and was highest among adult males. Summer seroprevalence increases tracked with the oestrid index from the previous year, icing and snowing events, and precipitation from the same year but decreased with growing degree days in the same year. Seroprevalence of E. rhusiopathiae varied more during the later years of the study. Our findings provide key insights into the influence of environmental factors on disease prevalence that can be instrumental for anticipating and mitigating diseases associated with climate change among Arctic wildlife and human populations.

An experimental model to induce digital dermatitis in beef calves.

BACKGROUND: Digital dermatitis (DD) is a multifactorial infectious disease affecting the skin on feet of cattle causing erosion and inflammation above the heel bulbs. Some cases of DD cause lameness and significantly impact animal welfare and productivity. While DD has emerged as a concern for the beef industry, key information regarding early detection and its impact on cattle behaviour is lacking. The primary objective of this study was to determine if an established DD experimental model for dairy calves could be used to induce DD lesions in beef calves. A secondary objective was to describe changes in behaviour and pain associated with induction of DD lesions. Eight beef calves acquired from a single cow-calf operator were enrolled in the study. Upon enrolment, calves were evaluated and determined to be free of foot lesions. Within the experimental environment, calves were housed in individual pens and assigned to two groups (mock-inoculated and inoculated). Both hind feet of each calf were enrolled. Within calf, inoculation protocol was consistent, and a 28-day experimental protocol was employed. Two days prior to inoculation, both hind feet of each calf were abraded (area above the heel bulbs and below the dewclaws), moistened, and wrapped to facilitate an anaerobic condition. Feet were inoculated with macerated DD lesion material or mock inoculum and remained wrapped until clinical signs of DD or protocol endpoint. RESULTS: After a period of 14 to 18 days post inoculation, three of five inoculated calves developed clinical signs (lameness), and upon close inspection, DD lesions were present on at least one hind foot. Two of five inoculated calves did not develop lesions within 28 days. Zero of three mock-inoculated calves developed DD. Treponema spp. were detected by quantitative polymerase chain reaction from biopsies of induced lesions. Measurements of behaviour prior to disease induction were numerically different between DD affected and mock-inoculated calves. CONCLUSIONS: An experimental infection model established for dairy cattle was used to successfully induce acute DD lesions in three of five inoculated beef calves. This model can provide a framework to study intervention protocols and to evaluate the impact of DD on behaviour and pain.

Antibacterial treatment for exotic species, backyard ruminants and small flocks: a narrative review highlighting barriers to effective and appropriate antimicrobial treatment.

Antimicrobial resistance is a complex One Health issue that exists in both human and veterinary medicine. To mitigate this ever-growing problem, efforts have been made to develop guidelines for appropriate antimicrobial use (AMU) across sectors. In veterinary medicine, there are notable literature gaps for proper AMU in minor species. We conducted a structured narrative review covering the years of July 2006 - July 2021 to find antimicrobial treatments for common bacterial infections in exotic (birds, rodents, reptiles, and others), small flock (chickens, turkeys, and other fowl), and backyard small ruminant (sheep and goats) species. We retrieved a total of 4728 articles, of which 21 articles met the criteria for our review. Studies were grouped according to species, syndrome, and body system affected. Other data extracted included the bacterial pathogen(s), treatment (active ingredient), and geographical origin. Body systems reported included: intra-oral (n = 4), gastrointestinal (n = 1), respiratory (n = 2), reproductive (n = 1), skin (n = 3), aural (n = 1), ocular (n = 4), and other/multisystem (n = 5). By species, our search resulted in: rabbit (n = 5), rat (n = 2), guinea pig (n = 1), chinchilla (n = 1), guinea pig and chinchilla (n = 1), avian species (n = 1), psittacine birds (n = 2), loris and lorikeets (n = 1), turtles (n = 2), lizards (n = 1), goats (n = 2) and sheep (n = 2). The results of our findings identified a distinct gap in consistent antimicrobial treatment information for commonly encountered bacterial conditions within these species. There is a persisting need for clinical trials that focus on antibacterial treatment to strengthen the evidence base for AMU within exotic, small flock, and backyard small ruminant species.

Producer Perceptions Toward Prevention and Control of Lameness in Dairy Cows in Alberta Canada: A Thematic Analysis.

Lameness in dairy cattle poses both an animal welfare and economic threat to dairy farms. Although the Canadian dairy industry has identified lameness as the most important health issue, lameness prevalence in the province of Alberta has not decreased over the last decade. Factors related to lameness have been reported, but the prevalence remains high. Therefore, this study was conducted to investigate dairy producers' perceptions on lameness and how these perceptions influence lameness prevalence in their cows. Qualitative interviews with open-ended questions were conducted with nine dairy producers in Alberta, Canada presenting farms with a wide variety of lameness prevalence. Thematic analysis of these interviews revealed five major themes, as well as five distinct types of producers regarding their perceptions. All nine producers mentioned similar challenges with lameness prevention and control. Identifying lameness, taking action, delays in achieving success, various approaches to prevention and control strategies, and differences between farms were the challenges encountered. However, producers' attitudes when dealing with these challenges varied. We concluded that understanding producers' perceptions is essential as no "one size fits all", when advising them regarding how to address lameness, as guidance and support will be most successful when it is aligned with their viewpoint.

Knowledge Gaps in the Understanding of Antimicrobial Resistance in Canada.

Current limitations in the understanding and control of antimicrobial resistance (AMR) in Canada are described through a comprehensive review focusing on: (1) treatment optimization; (2) surveillance of antimicrobial use and AMR; and (3) prevention of transmission of AMR. Without addressing gaps in identified areas, sustained progress in AMR mitigation is unlikely. Expert opinions and perspectives contributed to prioritizing identified gaps. Using Canada as an example, this review emphasizes the importance and necessity of a One Health approach for understanding and mitigating AMR. Specifically, antimicrobial use in human, animal, crop, and environmental sectors cannot be regarded as independent; therefore, a One Health approach is needed in AMR research and understanding, current surveillance efforts, and policy. Discussions regarding addressing described knowledge gaps are separated into four categories: (1) further research; (2) increased capacity/resources; (3) increased prescriber/end-user knowledge; and (4) policy development/enforcement. This review highlights the research and increased capacity and resources to generate new knowledge and implement recommendations needed to address all identified gaps, including economic, social, and environmental considerations. More prescriber/end-user knowledge and policy development/enforcement are needed, but must be informed by realistic recommendations, with input from all relevant stakeholders. For most knowledge gaps, important next steps are uncertain. In conclusion, identified knowledge gaps underlined the need for AMR policy decisions to be considered in a One Health framework, while highlighting critical needs to achieve realistic and meaningful progress.

Risk factors for digital dermatitis in free-stall-housed, Canadian dairy cattle.

BACKGROUND: A comprehensive analysis of the relation between digital dermatitis (DD) and cow and herd characteristics in Canadian dairies is currently lacking. METHODS: A multilevel logistic regression analysis was performed using 12,260 cow records from 62 dairy farms to assess association between 27 cow and herd-level variables, and presence of DD. RESULTS: The odds for a cow to have at least 1 DD lesion were higher in first-parity cows and those in later lactation (≥45 days in milk). Housing cows on a concrete base was associated with higher odds (OR 2.24) for DD when bedding was added once a week or less. Bedding the concrete base more frequently reduced odds for DD. Wood shavings or other bedding types were more positively associated with DD (OR 2.31 and 1.87, respectively) compared to sawdust. Also, the odds of DD were lower on farms with a scraping manure frequency of every 2 h compared to less frequent scraping (OR 0.54). CONCLUSION: Nine risk factors for DD were identified and quantified, with stall base, bedding type, and manure scraping frequency associated with lower odds of DD. DD prevalence could be reduced by implementing management practices for first-parity cows, as they had higher odds of DD.