Rehydration post-transport: duration of oral fluid therapy on behavior, biochemical measures of hydration, and health of neonatal dairy calves.

The objective of this study was to determine the impact of 0, 1, 2, or 3 d of oral electrolyte solutions (OES) following transport on calf behavior, biochemical measures of hydration, and subsequent health. Two cohorts of 60 Holstein bull calves ~3 to 7 d of age were included in this experiment. Calves (n = 30/treatment) were randomized to 1 of 4 treatments on arrival at a calf-raising facility: (1) 1-d OES, (2) 2-d OES, (3) 3-d OES, or (4) no OES (control). Calves were evaluated for signs of arthritis, depression, dehydration, diarrhea, fever, navel inflammation, and respiratory disease on arrival (day 0) and 1, 2, 3, and 7 d after arrival. Blood was obtained following each examination to assess biochemical measures of hydration, including serum electrolytes, glucose, hematocrit, lactate, pH, and serum total protein (STP). Calves were fitted with 3D accelerometers attached to the right hind leg along the metatarsus bone to continuously measure lying time. Linear regression models with Gaussian or Poisson link functions were used to test differences between treatments in blood parameters, as well as disease frequency and behavior, respectively. Calves spent the most time lying immediately post-transport (day 0); however, there was no effect of OES treatment on lying time. On arrival, 90% (95% CI: 84.6% to 95.4%) of calves had mild to moderate dehydration, and there was no significant difference in hydration status across treatments. Mildly dehydrated calves that received 1- and 2-d OES had higher STP concentration compared to the control. Moderately dehydrated calves that received 3- vs. 1-d OES had higher (101.4 vs. 93.7 mmol/L, respectively; P = 0.01) glucose concentration, and 3- vs. 2-d OES (101.4 vs. 96.2, respectively; P = 0.07) calves tended to have higher glucose concentration. The prevalence of failed transfer of passive immunity (STP < 5.1 g/dL) and hypoglycemia (glucose < 4.95 mmol/L) was 26.7% (18.6% to 34.7%) and 76.5% (68.7% to 84.2%), respectively. The frequency of moderate dehydration was lower for calves that received 2-d OES compared to the control (count ratio: 0.4; 0.2% to 0.8%; P = 0.009). These results underline the need for more research on rehydration strategies to help inform calf processing protocols. Future research should investigate preconditioning strategies to minimize the impact of marketing and transport on dairy calves. Continued nutritional-based research is also needed to better support calves' recovery post-transport.

Most male calves are sold and transported from the dairy farm soon after birth. Typically, calves are transported without access to milk and/or water, and they often arrive at calf-raising facilities with varying degrees of dehydration. This study provided calves with 0 (control), 1, 2, or 3 consecutive days of oral electrolyte solutions following transportation and assessed calf behavior, biomarkers of hydration, and subsequent health post-transport. Most calves were dehydrated and hypoglycemic (low blood glucose levels) on arrival at the calf-raising facility. Calves spent the most time lying immediately post-transport; however, electrolytes did not impact total lying time, the number of lying bouts, or lying bout duration. Providing calves with electrolytes for 2 d improved moderate dehydration (assessed via skin tent test) compared to the control. These results suggest that providing calves with 2 consecutive days of electrolytes following transportation can improve hydration status; however, more research is needed to mitigate dehydration prior to arrival at calf-raising facilities.

Dairy producers' colostrum practices, marketing, and attitudes toward male dairy calves.

Optimal early-life care of surplus calves born on dairy farms is critical for health and welfare. This cross-sectional study aimed to describe the marketing practices of male dairy calves, differences in the colostrum management between male and female calves on dairy farms, and the relationship between discrepant colostrum practices and dairy producers' attitudes toward male calf care. United States dairy producers (n = 1,000) in the states of Florida, Michigan, Ohio, Vermont, and Wisconsin were selected using stratified random sampling. A questionnaire containing questions about farm demographics, colostrum management (including quantity and timeliness of colostrum delivery), and producers' attitudes toward male calf care was mailed in February 2021. Attitudes toward male calf care were assessed using 5-point Likert scales for 10 statements regarding perceptions of the value of male calves and barriers in providing optimal care. Producer responses to questions about the quantity and timeliness of colostrum delivery between male and female calves were compared using a nonparametric Wilcoxon rank-sum test. Multivariable logistic regression models were used to investigate the association between differences in colostrum management and producers' attitudes. By May 2021, 953 surveys were delivered and 315 (33.1%) were returned with complete responses. Most producers (>90%) reported feeding equal volumes of colostrum and performing the first postbirth feeding within a similar time frame for male and female calves. However, compared with females, male calves had a longer delay to the first colostrum feeding. Approximately 40% of producers marketed their male calves through auctions, and over half (54.6%) of farms sold the male calves between 3 and 10 d of age. Large farms (≥500 lactating cows) were found to market male calves at a younger age (≤3 d of age). Most producers (>78%) believed their male calves were receiving optimal care and did not consider the workload and financial costs as obstacles to providing good care to male calves. However, those who viewed the workload as an obstacle to good care and produced organic products were marginally more likely to feed a lower volume of colostrum to male calves in the first feeding after birth. These findings suggest that interventions to improve colostrum practices should be more broadly targeted to all calves born on dairy farms, and that age at transport is markedly different between large and small farms.

A survey of antimicrobial use practices on veal farms in the United States.

Neonatal veal calves are highly susceptible to bacterial diseases. Occasional sub-optimal early-life care and long-distance transportation result in high disease burden and antimicrobial treatment incidence. Nonetheless, judicious use of antimicrobials is necessary to mitigate the animal and human health impacts of antimicrobial resistance. The objective of this cross-sectional study was to use a clinical vignette-based survey approach to evaluate the potential for reduced group or individual therapeutic antimicrobial use. The survey included items probing the adherence to veterinary-written protocols, antimicrobial use (AMU) at the calf- and group-level, and the treatment actions to case vignettes of calf diarrhoea, pneumonia, and navel infection. The survey was mailed to all veal calf producers within two U.S. production companies (n = 32 producers in Company 1; n = 70 producers in Company 2) in February and December 2019, respectively. The overall survey response rate was 36% (21/59). Although 95% of producers reported having veterinary-written treatment protocols for diarrhoea, pneumonia, and navel infection, veal producers infrequently (<50% of the time) referenced these protocols. Veal producers were primarily trained for disease identification and treatment by observing other personnel "on-the-job" (81%). Veal producers reported a high incidence of calf diarrhoea relative to pneumonia and naval infection, a lower percentage (≤40%) of diarrhoea cases being treated individually with antimicrobials. Using clinical vignettes, our results suggest that AMU decisions among veal producers depend on the severity of clinical signs for diarrhoea and pneumonia, while navel infections are often treated with antimicrobials regardless of sign severity. Nearly two-thirds of veal producers reported treating uncomplicated cases of diarrhoea (watery stool with normal body temperature, activity, and appetite), more than previously reported from dairy producers (37.1%). Findings from this survey suggest that calf producer-focused training to guide antimicrobial treatment decisions and improve producer adherence to veterinary-written treatment protocols may have important impacts on judicious antimicrobial use.

Antimicrobial resistance of Escherichia coli from dairy farms participating in an antimicrobial stewardship educational program for farm employees.

Antimicrobial use in food-producing animals is under increasing scrutiny due to the potential effect on the selection of antimicrobial-resistant bacteria that may be transmitted to humans by direct contact, with the food chain, or the environment. Novel data monitoring commensal Escherichia coli from dairy farms is essential for understanding antimicrobial resistance (AMR) patterns and their association with herd health management practices. The objectives of this study were to: (1) compare the prevalence of antimicrobial resistance in the E. coli isolates from the hospital, fresh, and mid-lactation pens from 18 conventional dairy farms participating in an educational training program in antimicrobial stewardship practices in California and Ohio, and (2) to characterize the prevalence of antimicrobial resistance of commensal E. coli isolated from pooled fecal pat samples before and 3 mo after participating in the educational training program. Pooled fecal pat samples were collected from the hospital pen, the fresh pen (1 to 5 DIM), and the mid-lactation pens (90 to 150 DIM) on conventional dairies in CA (n = 9) and OH (n = 9). Fecal samples were collected as part of a larger study using a quasi-experimental design that assigned farms to the training intervention group (TG; 6 per state) or the control group (CG; 3 per state). For the TG, farm worker(s) identified as having the task of diagnosis and treatment of adult cows on the farm participated in a training program on antimicrobial stewardship practices. Pooled fecal samples (n = 7) were collected at enrollment and 3 mo after completing the intervention on each of the participating farms (n = 18), followed by culture for E. coli isolation and antimicrobial sensitivity testing using the broth microdilution methodology. Logistic regression models were used to evaluate the association between E. coli antimicrobial resistance patterns with the training intervention and farm-level factors. No effect was observed in the prevalence of resistant isolates between the control and intervention farms after the training was delivered. Isolates from the hospital pens were 2.48 (95% CI: 1.06-6.22, P = 0.03) and 5.61 (95% CI: 1.94-16.91, P < 0.001) times, more likely to be resistant to streptomycin and chloramphenicol, respectively, than isolates from the mid-lactation pens. Our findings indicate there was a higher prevalence of AMR in E. coli associated with the hospital pen within the farm, while the training program for 3 mo did not affect the prevalence of AMR in E. coli on the farms participating in the program. Further research efforts should be conducted to identify factors driving AMR at the pen level, as well as approaches that could be used to reduce the risk of disseminating AMR from sick pens to animals being housed and to other pens on the farm.

How can better calf care be realized on dairy farms? A qualitative interview study of veterinarians and farmers.

Improving health and welfare outcomes for replacement and surplus dairy calves is important for the sustainability of the dairy industry. Dairy farmers and veterinarians hold expertise in calf management and have valuable perspectives on how to practically motivate improvements. The objective of this study was to determine strategies that could improve the care calves receive on dairy farms from the perspective of dairy farmers and their herd veterinarians. Two veterinary clinics specializing in dairy practice in British Columbia, Canada, and 21 of their client dairy farms participated in the project. Following a meeting in which calf colostrum management was discussed between farmers and their herd veterinarian, participant interviews were conducted. Separate interviews were conducted for the farmers (n = 27 farmers from 21 farms) and their herd veterinarians (n = 7, with 1 to 5 farms that each vet worked with enrolled in the study) using tailored semi-structured question guides. Interviews (n = 42) were transcribed and coded following inductive thematic analysis methodology. The themes identified included strategies for farmers, veterinarians, and calf buyers, as well as contexts that influenced the dairy farmers' internal motivation to provide good calf care. Results indicated that farmers could optimize their calf management through fostering engagement of calf care personnel or by enlisting technology. Veterinarians could provide support to farms by being actively involved in calf monitoring, assisting in developing operating protocols, and setting goals, and especially by using farm-specific data to guide their management recommendations. Calf buyers could communicate with and provide accountability to farmers and improve their purchasing strategies to encourage farms to raise more vigorous surplus calves. Farmers' personal values, social networks, and relationships with different dairy industry stakeholders influenced their concern about the standards of their calf care practices. These findings provide guidance on how dairy farmers could achieve or be prompted to achieve improvements in their calf care practices.

Evolution of influenza A viruses in exhibition swine and transmission to humans, 2013-2015.

AIMS: Swine are a mixing vessel for the emergence of novel reassortant influenza A viruses (IAV). Interspecies transmission of swine-origin IAV poses a public health and pandemic risk. In the United States, the majority of zoonotic IAV transmission events have occurred in association with swine exposure at agricultural fairs. Accordingly, this human-animal interface necessitates mitigation strategies informed by understanding of interspecies transmission mechanisms in exhibition swine. Likewise, the diversity of IAV in swine can be a source for novel reassortant or mutated viruses that pose a risk to both swine and human health. METHODS AND RESULTS: In an effort to better understand those risks, here we investigated the epidemiology of IAV in exhibition swine and subsequent transmission to humans by performing phylogenetic analyses using full genome sequences from 272 IAV isolates collected from exhibition swine and 23 A(H3N2)v viruses from human hosts during 2013-2015. Sixty-seven fairs (24.2%) had at least one pig test positive for IAV with an overall estimated prevalence of 8.9% (95% CI: 8.3-9.6, Clopper-Pearson). Of the 19 genotypes found in swine, 5 were also identified in humans. There was a positive correlation between the number of human cases of a genotype and its prevalence in exhibition swine. Additionally, we demonstrated that A(H3N2)v viruses clustered tightly with exhibition swine viruses that were prevalent in the same year. CONCLUSIONS: These data indicate that multiple genotypes of swine-lineage IAV have infected humans, and highly prevalent IAV genotypes in exhibition swine during a given year are also the strains detected most frequently in human cases of variant IAV. Continued surveillance and rapid characterization of IAVs in exhibition swine can facilitate timely phenotypic evaluation and matching of candidate vaccine strains to those viruses present at the human-animal interface which are most likely to spillover into humans.

How benchmarking motivates colostrum management practices on dairy farms: A realistic evaluation.

This study used realistic evaluation to determine how, and in which circumstances, providing dairy farmers with benchmarked data on their calves can motivate improved colostrum management practices. Dairy farmers from British Columbia, Canada, were recruited through 2 veterinary clinics that offered benchmarking of calf data as part of their services. For approximately 8 wk, blood samples were collected from newborn calves to evaluate serum total protein concentrations as an indicator of the effectiveness of the farmer's colostrum management. These data were analyzed separately for heifer calves ("replacement calves") and non-replacement calves, including males and beef crossbred females ("surplus calves"). The results of these analyses were benchmarked against other participating herds and presented to dairy farmers (n = 27) by their herd veterinarian (n = 7). Follow-up interviews were conducted separately with the farmers and veterinarians after each meeting to determine their perspectives on the utility of this benchmarking strategy. Therefore, a total of 42 interviews were coded, and realistic evaluation was used to determine common contexts and mechanisms that contributed to the success or failure of the benchmark meeting, with success characterized by farmers' expressed intention to improve their colostrum management practices. Four important contexts were identified that influenced the outcome of the benchmark meetings: (1) farm resources (e.g., facility limitations), (2) the farmer's perception of their calf performance, (3) management strategies, and (4) the farmer's personal values. Depending on these contexts, some farmers intended to improve their calf care practices based on resources the benchmark meeting provided, which included illustrative data and veterinary advice. These resources motivated change through influencing farmer decision-making, which depended on the value they saw in the data as a decision-making tool. The economic or moral interest farmers expressed in their surplus calves also influenced whether farmers intended to implement management changes. Recommendations for future implementation of benchmarking include targeting producers who are motivated to improve and who value the future performance of their calves, those who have engaged calf care personnel, and those who prefer data-driven decision-making. This study supports the important role veterinarians can play in motivating improved calf care practices through providing benchmarking services.

Serum total protein concentrations in surplus dairy calves in British Columbia.

Objective: This cross-sectional study aimed to evaluate serum total protein (STP) concentrations in surplus calves in British Columbia and explore associated factors including calf breed, sex, hydration, month of sampling, and frequency of calf pickup. Animal: Neonatal dairy and dairy-beef crossbred calves recently purchased from dairy farms and transported to an assembly facility. Procedure: Calves included in this study (N = 1449) were assessed at an assembly facility from March to August 2021, and blood samples were collected to measure STP as an indicator of transfer of passive immunity (TPI). Associations between STP and calf characteristics (breed, sex, hydration), month of sampling, and how frequently calves were collected from the source dairy farms (daily versus twice weekly or less) were evaluated with a linear regression model including farm as a random effect. Results: Of the 1433 serum samples, 24% had STP concentrations that were "poor:" defined as < 5.1 g/dL, and the proportion with poor STP varied widely among farms. Dairy-beef crossbred calves and calves that were dehydrated had higher STP concentrations, whereas those sampled in July had lower STP. This study was limited to calves purchased by 1 calf buyer but represented a large number of calves from 12% of the dairy farms in British Columbia. Conclusion: Approximately 1/4 of surplus dairy calves had poor STP concentrations. Clinical relevance: Ensuring surplus dairy calves have successful TPI is an important opportunity to bolster their health and welfare.

Concentrations sériques des protéines totales chez les veaux laitiers excédentaires en Colombie-Britannique. Objectif: Cette étude transversale visait à évaluer les concentrations sériques des protéines totales (STP) chez les veaux excédentaires en Colombie-Britannique et à explorer les facteurs associés, notamment la race de veau, le sexe, l'hydratation, le mois d'échantillonnage et la fréquence de ramassage des veaux. Animal: Veaux nouveau-nés issus de croisements laitier et laitier-boeuf achetés récemment à des fermes laitières et transportés vers une installation commune. Procédure: Les veaux inclus dans cette étude (N = 1449) ont été évalués dans une installation commune de mars à août 2021, et des échantillons de sang ont été prélevés pour mesurer les STP comme indicateur du transfert de l'immunité passive (TPI). Les associations entre les STP et les caractéristiques des veaux (race, sexe, hydratation), le mois d'échantillonnage et la fréquence à laquelle les veaux ont été ramassés dans les fermes laitières d'origine (quotidiennement versus deux fois par semaine ou moins) ont été évaluées avec un modèle de régression linéaire incluant la ferme comme effet aléatoire. Résultats: Sur les 1433 échantillons de sérum, 24 % présentaient des concentrations de STP « médiocres ¼ définies comme < 5,1 g/dL, et la proportion avec des STP médiocres variait considérablement d'une ferme à l'autre. Les veaux issus de croisements lait-boeuf et les veaux déshydratés présentaient des concentrations de STP plus élevées, tandis que ceux échantillonnés en juillet présentaient des concentrations de STP plus faibles. Cette étude se limitait aux veaux achetés par un acheteur de veaux, mais représentait un grand nombre de veaux provenant de 12 % des fermes laitières de la Colombie-Britannique. Conclusion: Environ le quart des veaux laitiers excédentaires avaient de faibles concentrations de STP. Pertinence clinique: Veiller à ce que les veaux laitiers excédentaires aient un transfert d'immunité passive réussie est une occasion importante de renforcer leur santé et leur bien-être.(Traduit par Dr Serge Messier).

Antimicrobial stewardship on the dairy: Evaluating an on-farm framework for training farmworkers.

Dairy farmworkers are commonly responsible for disease diagnosis and routine treatment decisions for cattle. This highlights the importance of farmworkers' knowledge and skills to successfully implement judicious use of antimicrobials in livestock production systems. The main objectives of this project were to develop and evaluate an on-farm educational program for farmworkers in antimicrobial stewardship in adult dairy cattle. A longitudinal quasi-experimental study design was used, by enrolling 12 conventional dairy farms in the United States (6 in California and 6 in Ohio). Farmworkers responsible for treatment decisions on the farm (n = 25) participated in a didactic and hands-on 12-wk antimicrobial stewardship training program led by the investigators. All antimicrobial stewardship training materials were available in Spanish and English. Interactive short videos with audio were developed to cover the learning objectives for each of the 6 teaching modules: antimicrobial resistance, treatment protocols, visual identification of sick animals, clinical mastitis, puerperal metritis, and lameness. Pre- and post-training assessments were administered using an online training assessment tool to evaluate changes in knowledge and attitudes about antimicrobial stewardship practices. Cluster analysis and multiple correspondence analyses were conducted to evaluate the association among categorical variables for participants' level of change in knowledge and its association with language, farm size, and state. A 32% average increase in knowledge was observed through an assessment conducted after completing the antimicrobial stewardship training, compared with the pre-training assessment. A significant improvement in 7 of 13 attitude questions related to antimicrobial stewardship practices on the farm was observed. Knowledge and attitude scores of participants on antimicrobial stewardship and identification of sick animals significantly improved after completing the antimicrobial stewardship training. The results observed in this study support the relevance of antimicrobial stewardship training programs targeting farmworkers to improve antimicrobial drug use knowledge and skills.

A scoping review of neonatal calf diarrhea case definitions.

Various case descriptions and scoring systems have been used to define neonatal calf diarrhea (NCD) and diverse diarrhea-related outcomes are reported, which limits direct comparison between studies. Therefore, the objective of this scoping review was to characterize the case definitions used for NCD and describe diarrhea-related outcomes to inform future efforts towards standardization. A literature search identified articles using 3 databases (Medline, CAB Direct, Agricola), along with Google and Google Scholar. This returned 16,854 unique articles, which were then screened for eligibility by two independent reviewers, resulting in 555 being selected for data extraction. Among articles, the study populations included mostly dairy-breed calves (88%; n = 486) while the remainder evaluated beef, crossbred, or dual purpose beef/dairy calves (10%; n = 53), or did not report breed (3%; n = 16). Studies used between 1 and 8 metrics to define NCD, with 933 unique metrics extracted in total. The most common metric was fecal consistency alone (30%; n = 281), or with at least 1 other metric (26%; n = 241). To define diarrhea, fecal consistency was either described qualitatively (e.g., "profuse liquid feces"), or semi-quantitatively, for example using a scoring system that frequently included 4 levels (n = 208). Some NCD case definitions included fecal color, volume, or odor (10%; n = 98), physical exam parameters (8%; n = 79), the duration of abnormal feces (7%; n = 67), the presence of abnormal contents (e.g., blood, 7%; n = 61), farm treatment records (6%; n = 54), fecal dry matter (1%; n = 12), or another metric (4%; n = 41). One or more references were cited for the NCD case definition by 49% of studies (n = 273/555), with the most common references being Larson et al. (1977) (n = 85), and McGuirk (2008) (n = 59). In the 555 included articles, 979 unique diarrhea-related outcomes were found, most commonly a binary categorization of calves having or not having diarrhea (49%; n = 483). Other articles reported statistical outcomes calculated from fecal scores (16%; n = 159), multiple diarrhea severities (10%; n = 95), or the age calves first developed NCD (8%; n = 76). This review characterized substantial heterogeneity among NCD case definitions and diarrhea-related outcomes, which limits interpretation and comparison of studies. Future work is required to develop and validate reporting standards for NCD to optimize knowledge synthesis and support rigorous and ethical calf health research.

A survey of male and female dairy calf care practices and opportunities for change.

The primary objective of this study was to compare male and female dairy calf management practices and evaluate risk factors associated with differences in care. Secondary objectives were to understand surplus calf transportation and marketing practices and investigate incentives to motivate calf care improvements. An online survey was distributed to all dairy producers in Ontario (n = 3,367) from November 2020 to March 2021 and Atlantic Canada (n = 557) from April to June 2021. Dairy producers were identified through provincial dairy associations and contacted via e-mail and social media. Descriptive statistics were computed, and a logistic regression model was created to evaluate factors associated with using discrepant feeding practices (i.e., fed less colostrum, fed colostrum later, or fed raw, unsalable milk) for male calves compared with females. The survey had a 7.4% response rate (n = 289/3,924) and was primarily filled out by farm owners (76%). Although colostrum and milk feeding practices were similar between male and female calves, male calves received less milk while still on the dairy farm of origin compared with females. Male calves were also more likely to be fed a higher proportion of raw, unsalable milk. Female producers and those that kept their male calves beyond 10 d of age had lower odds of using poorer feeding practices for male calves. Male calves were mostly sold between 1 and 10 d (64%), primarily through direct sales to a calf-rearing facility (45%), with auctions being the next most common method (35%). A small but notable proportion of producers (18%) agreed that euthanizing male calves is a reasonable alternative when their sale price is very low; however, few producers (13%) reported that financial costs limited their male calf care. The largest proportion (43%) of producers reported that a price premium for more vigorous calves would motivate them to take better care of their male calves. Conversely, only 28% of producers reported that a price discount for calves in poor condition would be motivating. Producers placed importance on the opinion of their calf buyer, their herd veterinarian, and the Canadian Code of Practice for the Care and Handling of Dairy Cattle when considering their calf care practices, and they highly valued practices that promote calf health. Respondents to this survey reported a lower proportion of tiestall barn use and higher milk productivity compared with typical dairy herds in the region, suggesting selection bias for more progressive dairy producers. Nevertheless, our results suggest that dairy producers provide similar care between male and female calves, but some male calves experience challenges due to milk feeding and marketing practices. Feedback from calf buyers along with continued support and guidance from herd veterinarians and the Code of Practice may motivate dairy producers to improve male calf care.

Antimicrobial Use and Resistance in Surplus Dairy Calf Production Systems.

Surplus calves, which consist predominately of male calves born on dairy farms, are an underrecognized source of antimicrobial-resistant (AMR) pathogens. Current production systems for surplus calves have important risk factors for the dissemination of pathogens, including the high degree of commingling during auction and transportation and sometimes inadequate care early in life. These circumstances contribute to an increased risk of respiratory and other infectious diseases, resulting in higher antimicrobial use (AMU) and the development of AMR. Several studies have shown that surplus calves harbor AMR genes and pathogens that are resistant to critically important antimicrobials. This is a potential concern as the resistant pathogens and genes can be shared between animal, human and environmental microbiomes. Although knowledge of AMU and AMR has grown substantially in dairy and beef cattle systems, comparable studies in surplus calves have been mostly neglected in North America. Therefore, the overall goal of this narrative review is to summarize the existing literature regarding AMU and AMR in surplus dairy calf production, highlight the management practices contributing to the increased AMU and the resulting AMR, and discuss potential strategies and barriers for improved antimicrobial stewardship in surplus calf production systems.

The Impact of Overstocking and Negative Energy Balance on Quantitative Measurement of Non-typhoidal Salmonella in Periparturient Dairy Cattle.

Stressful conditions in animal production facilities may exacerbate the fecal shedding and foodborne transmission of non-typhoidal Salmonella enterica subsp. enterica. Dairy cows are reservoirs of this zoonotic microorganism, and its prevalence has roughly doubled in the past decade on dairy farms in United States. Dairy cows are commonly overstocked at the feed bunk, and stressors placed on the animal prior to parturition may exacerbate Salmonella shedding. However, no studies have evaluated the impact of overstocking and metabolic stress on fecal concentrations of the pathogen. Therefore, we conducted a field trial with 120 multiparous dairy cows randomized into one of four treatment groups with different stocking densities at the feed bunk during the periparturient period as follows: US, understocked from -60 to -1 DRC; OS, overstocked from -60 to -1 DRC; USOS, understocked from -60 to -26 DRC/overstocked from -25 to -1 DRC; and OSUS, overstocked from -60 to -26 DRC/ understocked from -25 to -1 DRC. Fecal and blood samples were collected at four time points relative to calving. qPCR assays were used to quantify Salmonella invA gene and total bacterial community from fecal samples, and a subset of isolates recovered from fecal bacterial culture were characterized using pulsed field gel electrophoresis and serotyping. Serum non-esterified fatty acids (NEFA) were measured as a metabolic stress indicator using an immunoassay. Multivariable analyses were performed to test if changes in Salmonella concentrations were associated with stocking density, energy balance, or days relative to calving. From fecal isolates, three Salmonella serovars were identified, S. Cerro; Kentucky; Meleagridis. Concentrations of Salmonella increased as cows approached calving. Higher stocking densities at the feed bunk did not impact total bacterial community or NEFA; however, cows in the overstocked groups had higher Salmonella fecal concentrations. Further, cows with higher NEFA concentrations after calving had a higher likelihood of detection of Salmonella. Future farm interventions should aim to reduce environmental and metabolic stress during the periparturient period to decrease the dissemination of Salmonella to cattle, the environment, and humans.

Prevalence and Sources of Salmonella Lymph Node Infection in Special-Fed Veal Calves.

ABSTRACT: Peripheral lymph nodes (LNs) have been implicated as potential contaminants of ground beef, yet the source and timing of Salmonella LN infection in cattle is still unclear, limiting targeted intervention. The aim of this study was to leverage the vertical integration of special-fed veal production to identify preharvest environmental exposures, specifically in livestock trailers and harvest facility holding pens where calves spend 30 min to 4 h, that result in Salmonella LN infection. Ten cohorts of 80 to 82 veal calves were followed through the harvest process, and environmental samples were collected in barns, trailers, and holding pens. Mesenteric LNs from 35 calves were collected at harvest, and 25 prefemoral LNs per cohort were pooled. Within the same cohort, for 12 samples for which the serovar of the environmental and calf LN Salmonella isolates matched, the isolates were submitted for whole genome sequencing to determine whether environmental exposure resulted in LN infection. Cohort-level Salmonella mesenteric LN prevalence ranged from 0% (0 of 35 samples) to 80% (28 of 35 samples), and pooled prefemoral LNs were positive for Salmonella in 3 of the 10 cohorts. Salmonella prevalence in samples from barns, livestock trailers, and harvest facility holding pens was 22% (13 of 60 samples), 74% (59 of 80 samples), and 93% (74 of 80 samples), respectively. Some environmental and LN isolates were multidrug resistant. Four instances of Salmonella transmission from trailers and/or holding pens to calf LNs were supported by sequence data. Salmonella serovars Agona, Give, and Muenster were identified in transmission events. One instance of transmission from the livestock trailer, two instances from holding pens, and one instance from either trailer or holding pens were observed. Further research is needed to evaluate the extent of environmental Salmonella transmission in cattle and to determine whether targeted interventions in trailers or holding pens could reduce novel Salmonella LN infection in veal calves before harvest.

Defining clinical diagnosis and treatment of puerperal metritis in dairy cows: A scoping review.

Although puerperal metritis (PM) is a common infectious disease in dairy cattle, there are currently discrepancies between clinical case definitions within and between available peer-reviewed literature and on-farms practices. The inconsistent use of PM criteria across studies and on-farms practices can result in disparities related to recommendations for treating cows, affecting judicious use of antimicrobials. The objective of this study was to systematically review the peer-reviewed literature for clinical signs used for case definition of PM. The criteria used included local (e.g., vaginal discharge) and systemic clinical signs of infection (e.g., fever, drop in milk). The Preferred Reporting Items for Systematic Review and Meta-Analysis extension for scoping reviews protocols were used to screen commonly used databases. Following this protocol, one reviewer screened title and abstract for eligibility (n = 2,096), followed by full-text screening of selected articles (n = 396) by 2 reviewers to confirm eligible articles (n = 174). The most frequently cited reference article (37.5%) for the definition of PM was published in 2006, followed by articles published between 1998 and 2009 (13%). In 40.2% of articles, no reference was provided for definition of PM; vaginal discharge was described in terms of color, odor, and viscosity when related to the PM definition. Terms used for description of vaginal discharge color were red-brown (61.4%), red (5.1%), brown (8.6%), chocolate (4%), white (1.7%), yellow (0.5%), pink (5.7%), or gray (0.5%); vaginal discharge color was not reported in 24.1% articles. The vaginal discharge odor was described as fetid (75.8%), putrid (5.1%), foul (10.3%), or other (5.7%; e.g., abnormal, malodorous, odoriferous); odor was not mentioned in 7.4% of articles. The vaginal discharge viscosity was described as watery (74.1%), purulent (27%), mucopurulent (8.6%), thin (4%), serous (2.8%), or abnormal (2.3%) and was not mentioned in 11.5% of articles. Fever was included in 59.7% of articles as a criterion for PM diagnosis. The most used rectal temperature threshold was ≥39.5°C (56.8%), followed by ≥39.2°C (2.8%). Approaches used for vaginal discharge evaluation included rectal palpation (37.3%), intravaginal exploration with a gloved hand (18.4%), Metricheck (9.8%), or speculum (5.7%); and in 28.7% of articles, diagnostic tools used were not mentioned. Many of the color and odor vaginal discharge descriptions observed in the literature, used synonymous words to describe the same vaginal discharge sample, highlighting a lack of terminology consensus that could result in disagreements, especially due to the subjective character of these clinical evaluations of vaginal discharge color and odor. Although select consensus articles are available, it is common for studies to disregard a reference when defining PM cases. Furthermore, our findings highlight the need for a robust and clear consensus on criteria and terminology used to diagnose PM.

The use of common antimicrobial agents in US veal calves.

The use of antimicrobials in food animals and the selection of antimicrobial-resistant pathogens continue to be prominent concerns for human food safety and public health. To provide optimal stewardship programs, antimicrobial use in animal production operations must be quantified and standardized for benchmarking and creating goals, monitoring temporal trends, and identifying causes of emerging resistance. In the United States, quantified estimates of antimicrobial use are available in dairy and beef cattle, but these data have not been generated for veal calf herds. Therefore, the objective of this study was to estimate the treatment incidence (TI) of antimicrobials for eight US veal calf farms in one rearing cycle. Treatment incidences were compared between calculated doses defined by the labeled daily dose (LDD), animal-defined daily dose (ADD) from the European Medicines Agency (EMA) guideline, and the used daily dose (UDD) from the farm treatment protocols. Among eight farms, veal calves received a mean of 34.40 LDD, 34.88 ADD, and 28.68 UDD of an antimicrobial per 100 days. The lower TI based on the UDD administration was a result of higher farm protocol dosing relative to the labeled and EMA daily doses. Higher quantities of antimicrobial administration were observed in the first three weeks (day 1-21) of rearing (Tukey-adjusted p < .05). This study is the first to quantitatively estimate the TI of antimicrobials on the US veal calf operations and serves as an important step toward the development of antimicrobial stewardship programs.

Prevalence and predictors of bacteremia in dairy calves with diarrhea.

Gastrointestinal disease is the most common cause of mortality in dairy calves. Septicemia is an important sequela of diarrhea, and the possibility of bacteremia is the primary justification for empirical antimicrobial therapy. Prior reports estimate that approximately one-third of diarrheic calves are bacteremic; however, those estimates may not be representative of routine cases in heifer calves on commercial dairy operations early in the course of disease. We hypothesized that the prevalence of bacteremia in calves with diarrhea and systemic signs of illness is less than prior estimates (∼31%), and that clinical signs or hematological values would be associated with the presence or absence of bacteremia. Female calves less than 21 d of age with and without diarrhea were enrolled from 2 commercial dairy farms over a 10-wk period. Diarrheic calves were enrolled if they were newly diagnosed, had loose to watery stool, had either dehydration (assessed by skin tent and eye position) or depression (assessed by suckle reflex and standing ability), and had no prior antimicrobial treatments. Complete health assessments were conducted at 0, 7, and 14 d following enrollment. An aseptic jugular venous sample was collected and cultured using aerobic and anaerobic methods, and bacterial species were identified using mass spectrometry. Poisson regression models were used to identify associations with bacteremia and compute adjusted prevalence ratios. The prevalence of bacteremia in diarrheic and healthy calves was 9.26% (10/108, 95% confidence interval: 4.5-16%) and 14.8% (4/27, 95% confidence interval: 1.4-28.2%), respectively. Among calves with diarrhea, those with a fever (>39.7°C) or depression were 4.8 and 6.5 times more likely, respectively, to have bacteremia. Only 1 of 47 calves (2%) without signs of depression was bacteremic. The prevalence of bacteremia in diarrheic calves with signs of systemic illness (depression or dehydration) was significantly lower than previous estimates, and bacteremia was rare among calves without observed depression. Antimicrobial therapy targeting bacteremia is not currently justified in routine cases of diarrhea in preweaning calves without signs of depression. These results suggest a substantial opportunity for more targeted antimicrobial therapy to improve antimicrobial stewardship.

Perspectives on the Management of Surplus Dairy Calves in the United States and Canada.

The care of surplus dairy calves is a significant issue for the United States and Canadian dairy industries. Surplus dairy calves commonly experience poor welfare as evidenced by high levels of mortality and morbidity, and negative affective states resulting from limited opportunities to express natural behaviors. Many of these challenges are a result of a disaggregated production system, beginning with calf management at the dairy farm of origin and ending at a calf-raising facility, with some calves experiencing long-distance transportation and commingling at auction markets or assembly yards in the interim. Thus, the objectives of this narrative review are to highlight specific challenges associated with raising surplus dairy calves in the U.S. and Canada, how these challenges originate and could be addressed, and discuss future directions that may start with refinements of the current system, but ultimately require a system change. The first critical area to address is the management of surplus dairy calves on the dairy farm of origin. Good neonatal calf care reduces the risk of disease and mortality, however, many dairy farms in Canada and the U.S. do not provide sufficient colostrum or nutrition to surplus calves. Transportation and marketing are also major issues. Calves can be transported more than 24 consecutive hours, and most calves are sold through auction markets or assembly yards which increases disease exposure. Management of calves at calf-raisers is another area of concern. Calves are generally housed individually and fed at low planes of nutrition, resulting in poor affective states and high rates of morbidity and mortality. Strategies to manage high-risk calves identified at arrival could be implemented to reduce disease burden, however, increasing the plane of nutrition and improving housing systems will likely have a more significant impact on health and welfare. However, we argue the current system is not sustainable and new solutions for surplus calves should be considered. A coordinated and holistic approach including substantial change on source dairy farms and multiple areas within the system used to market and raise surplus dairy calves, can lead to more sustainable veal and beef production with improved calf outcomes.

Longitudinal health outcomes for enteric pathogens in preweaned calves on Ohio dairy farms.

Calf gastrointestinal disease remains one of the main causes of productivity and economic losses on dairy operations. The majority of pre-weaned calf mortality is attributed to diarrhea or other digestive problems. Five enteric pathogens are commonly associated with diarrhea in dairy calves, including bovine rotavirus, bovine coronavirus, Escherichia coli, Salmonella spp., and Cryptosporidium parvum. Pathogen-associated differences in health outcomes and case fatality rates have not been well-characterized. Additionally, updated prevalence estimates may reflect important changes in the epidemiology of the pathogens on dairy farms. For this cohort study, fecal samples were collected from 276 clinically ill calves across 5 central Ohio dairy farms on the first day of diarrheal diagnosis. Genomic techniques, including reverse transcription polymerase chain reaction (RT-PCR) and droplet digital polymerase chain reaction (ddPCR) were used to test for the presence of the five enteric pathogens. A Poisson regression model was used to estimate the relative risk of mortality, and a survival analysis with a Cox regression model was used to analyze time to return to a healthy clinical status by pathogen. Rotavirus was the most frequently identified at 68.1 % (188/276), followed by F5 (K99)+E. coli at 42.5 % (114/268), C. parvum at 28.4 % (66/232), coronavirus at 5.8 % (16/276), and Salmonella had the lowest prevalence at 3.7 % (10/268). Risk of mortality tended to be higher for calves infected with Salmonella (RR = 3.83; 95 %CI: 0.93, 16.02, p = 0.062); however, the time to return to a healthy clinical status was not different for different pathogens. Only farm was a significant predictor of time to return to health (p = 0.017); the within-farm median duration of signs substantially varied between 2 and 7 days. The results suggest that the prevalence and distribution of rotaviral infections is higher than reported in prior studies. With the exception of infections caused by Salmonella spp., pathogen diagnosis on the first day of diarrhea was a poor predictor of the outcome and duration of disease. These results are critical to guide the implementation of prevention measures to detect, treat, and prevent calf diarrhea.

A focus group study of Ontario dairy producer perspectives on neonatal care of male and female calves.

Providing optimal calf care remains a challenge on many dairy farms and has important implications for the future health, welfare, and productivity of male and female calves. Recent research suggests that male dairy calves receive a lower quality of care early in life than female calves, but further investigation is required to determine the factors that influence this disparity. The objectives of this study were to understand dairy producer perspectives on neonatal calf care practices and explore differences between male and female calf care. Overall, 23 dairy producers in Ontario, Canada, participated in 4 focus groups about calf care practices that were recorded and evaluated qualitatively using thematic analysis. Major barriers for good calf care included lack of knowledge about the best management practices for calf care and the prioritization of farm resources toward the milking herd. Some producers also noted that farm infrastructure (particularly during challenging weather) and employee training were important limitations. The economic cost of providing good neonatal calf care was important primarily for male calves and acted as a motivation or a barrier depending on the producer's beliefs about calf care and how they chose to market their calves. The primary source of knowledge producers used to develop calf care practices was their own experience, although many also relied on dairy-industry advisors, most often veterinarians. Producers were motivated by social norms, along with intrinsic pride and obligation to provide good calf care, and these motives were influenced by their emotional state. Producers expressed beliefs about which aspects of calf care are most important-notably colostrum management-and appreciated simple and economical solutions to calf-rearing challenges. Calf care practices were varied, and we identified a diversity of knowledge, motivations, and barriers to adopting best management practices, which sometimes differed between male and female calves. Some producers said that they did not know what happened to their male calves after they left the farm and tended to prioritize the care of female over male calves in subtle ways, such as less timely provision of colostrum. The infrastructure investment and other costs associated with caring for male calves often limited their care, but producers were still motivated to provide adequate care for male calves. These findings represent potential targets for additional research and intervention strategies to improve calf care practices on dairy farms.