Risk factors for antimicrobial use in veal calves and the association with mortality

Associations of serostatus upon arrival with clinical respiratory disease, lung consolidation, and growth in veal calves

Respiratory tract infections remain a major problem during calf rearing, especially among milk (formula)-fed veal. Preconditioning of calves through appropriate colostrum management and vaccination could be helpful to address this issue. The objective of this study was to investigate whether the presence of serum antibodies against major respiratory tract pathogens (bovine respiratory syncytial virus, parainfluenza 3 virus, bovine coronavirus, Mycoplasmopsis bovis, Histophilus somni, Pasteurella multocida, and Mannheimia haemolytica) and total serum IgG concentration in calves upon arrival at the veal facility were associated with the occurrence of clinical bovine respiratory disease (BRD) or lung consolidation in the first 3 wk, as assessed by both the Wisconsin BRD scorecard (based on 5 clinical signs: cough, rectal temperature, ear position, and nasal and ocular discharge) and by quick thoracic ultrasound scanning. Additionally, the association between calves' serostatus production parameters were explored. A prospective cohort study was conducted among 442 male dairy calves on a large veal calf facility in Belgium. Both clinical scoring and quick thoracic ultrasound scanning were performed on all calves at 4 key moments in the production cycle: arrival at the facility, initiation of first metaphylactic antimicrobial treatment at peak incidence of BRD (wk 1), end of the first metaphylactic treatment (short-term evaluation) and at wk 10 (long-term evaluation). Mixed effects logit regression models were fitted to quantify relationships. The outcomes of interest were clinical respiratory disease (Wisconsin BRD scorecard positive), lung consolidation (≥1 cm or ≥ 3 cm), average daily weight gain, and cold carcass weight. In the first week of production, incidence of lung consolidation (≥1 cm) quickly increased from 14.9% upon arrival to 43.0% at the peak of the BRD incidence, while clinical BRD increased from 3.6% to 16.1%. The main finding of this study was that calves who were seropositive for bovine respiratory syncytial virus and bovine coronavirus at arrival had reduced odds of developing lung consolidation at the peak of the outbreak, 0.58 odds ratio (95% CI: 0.38-0.89) and 0.37 odds ratio (95% CI: 0.20-0.69), respectively. No relationships between serum IgG concentration at arrival and the development of lung consolidations or clinical respiratory disease were found. Nevertheless, on average, throughout the first 10 wk of the fattening cycle, calves with failed transfer of passive immunity (serum IgG < 7.5 g/L) gained 40 g/d (95% CI: 10-70 g/d) less weight (average daily gain). Hence, ensuring that calves have a positive serostatus for these respiratory tract pathogens before entering the facility may help lower the incidence of lung consolidations, subsequently reducing treatment incidence and the adverse effects on primary economic outcomes.

Investigation into the safety, and serological responses elicited by delivery of live intranasal vaccines for bovine herpes virus type 1, bovine respiratory syncytial virus, and parainfluenza type 3 in pre-weaned calves

Despite the fact that pneumonia remains a leading cause of mortality and morbidity in pre-weaned calves, relatively little is known regarding the effects of the concurrent administration of intranasal pneumonia virus vaccines, particularly in calves with high levels of maternally derived antibodies. The objective of this study was to use a cohort of 40 dairy and dairy-beef female and male calves (27 females and 13 males) to determine serological responses to concurrent administration at 3 weeks of age (22 ± 4.85 days) of two commercially available intranasal (IN) vaccines for the viruses: bovine respiratory syncytial virus (BRSV), bovine herpes virus 1 (BoHV-1), and parainfluenza-3-virus (PI3-V). The study groups were as follows: (i) Bovilis IBR Marker Live only® (IO), (ii) Bovilis INtranasal RSP Live® only (RPO), (iii) Concurrent vaccination with Bovilis IBR Marker Live® & Bovilis Intranasal RSP Live® (CV), and (iv) a control group of non-vaccinated calves (CONT). The calves' serological response post-IN vaccination, clinical health scores, rectal temperatures, and weights were measured. Data were analyzed in SAS using mixed models and logistic regression. The CV calves had an average daily weight gain (ADG) of 0.74 (±0.02) kg, which was similar to CONT (0.77 ± 0.02 kg). Despite no significant differences in the antibody levels between study groups 3 weeks post-IN vaccination, following the administration of subsequent parenteral injections in the form of Bovilis Bovipast RSP®(antigens; inactivated BRSV, inactivated PI3-V, inactivated Mannheimia haemolytica) and Bovilis IBR Marker Live®, the antibody levels of the BRSV and PI3-V increased in both the CV and RPO study groups. Concurrent vaccination resulted in no increase in fever and no difference in health scores when compared to CONT.

The Effects of Milk Replacer Supplemented with Ascophyllum nodosum as a Novel Ingredient to Prevent Neonatal Diarrhea in Dairy Calves and Improve Their Health Status

Nutrition and health during pre-weaning affect the calves' future fertility, calving age, production, and carrier length. Calves are highly susceptible to neonatal calf diarrhea (NCD), which can be fatal. NCD is due to hypovolemia and acidosis, which may involve anorexia and ataxia. The One Health principle calls for a drastic reduction in antimicrobial use. One approach is to improve animal health and reduce the use of antibiotics and functional ingredients that have beneficial effects due to bioactive compounds. Several functional ingredients and additives can be considered, and, in particular for this study, Ascophyllum nodosum was considered. The present study aimed to evaluate the role of A. nodosum as a functional ingredient implemented into the milk replacer in neonatal calves. Twelve pre-weaned Holstein Frisian calves, housed in twelve individual pens in the same environmental conditions, were divided into two groups of six animals: a control group (CTRL, n = 6) fed with a milk replacer, and a treatment group receiving milk enriched with 10 g of A. nodosum in their diet (TRT, n = 6) for 42 days. The fecal score was evaluated daily (3-0 scale) to monitor the incidence of diarrhea in the two groups. The body weight was evaluated weekly, and every two weeks feces were collected for microbiological evaluation using a selective medium for plate counting of total, lactic acid, and coliform bacteria. To verify the presence of Lactobacillus, Bifidobacterium, and Escherichia coli, real-time qPCR was used. At the beginning and at the end of the trial, blood samples were obtained for serum metabolite analysis. The growth performance did not differ in either of the two groups, but significant differences were observed in the incidence of moderate diarrhea (p-value < 0.0113), where the TRT group showed a lower incidence of cases during the 42-day period. Serum analysis highlighted higher contents of albumin, calcium, phosphorus, and total cholesterol in the TRT group compared to CTRL (p-value < 0.05). In conclusion, implementation of A. nodosum in the diet of calves can lead to better animal welfare and may reduce the use of antibiotics.

Case - Control study: Evaluation of plasma procalcitonin concentration as an indicator of inflammation in healthy and sick cows

This case - control study aims to evaluate Procalcitonin (PCT) plasma concentrations in healthy and hospitalized cows with a conclusive diagnosis of inflammation due to bacterial infection. Thirty-four healthy and 131 sick cows were included. Procalcitonin concentrations were assessed using an ELISA kit for cattle. Depending on whether sick cows received antimicrobial treatments prior to admission or not, they were divided in treated (TP) or not treated (NTP) subgroups. Mann-Whitney U tests were performed to determine differences between healthy vs sick cows, while Kruskal-Wallis with Dunn's multiple comparison test were applied for healthy vs sick subgroups. Receiver operating characteristic (ROC) analysis was performed to assess the optimal cut-off value. Kaplan-Meier survival curves were determined for cows belonging to the groups with PCT values below and above ROC cut-offs. Plasma PCT concentration was 200.1 (147.8-324.1) pg/mL and 361.6 (239.7-947.1) pg/mL in the healthy control and in the sick group, respectively (P < 0.001). The optimal cut-off value of plasma PCT concentration was 244.4 pg/mL (sensitivity 73.6%, specificity 60.0%). The plasma PCT concentration was 267.5 (210.3-771.2) pg/mL in the TP subgroup and 425.6 (253.1-1242) pg/mL in the NTP subgroup (P = 0.03). Cows with PCT above the ROC cut-off value had a reduced survival percentage and a higher mortality risk (P < 0.05). Procalcitonin showed the ability of differentiate healthy cows from hospitalized cows with a conclusive diagnosis of inflammation due to bacterial infection. Moreover, PCT was a good predictor of negative prognostic outcome.

Impact of early dam contact on veal calf welfare

Dairy calves, including surplus calves, are typically separated from their dam within hours of birth. The aim of this study was to assess the welfare impacts of raising surplus calves destined for veal with their dam for 2 or 4 weeks until transport. Surplus calves from one dairy farm were separated from their dam at birth (n = 39) or kept with the dam (n = 37) until transport to the veal farm at either 2 (n = 50) or 4 (n = 26) weeks of age, with abrupt separation for dam-reared calves. Calf measures of body weight, health, immunity, haematology and behaviour were recorded at the dairy and veal farms. Dam-reared calves had higher body weights in weeks 3, 4 and 5 at the DF, as well as at arrival at the veal farm, but by slaughter this advantage was lost. More dam-reared calves had fever in week 3 and showed signs of disease in week 5 at the dairy farm. Dam-reared calves did not differ in IgG, IgA or IgM levels but had higher counts of white blood cells, which could reflect a higher pathogen exposure rather than improved immunity. Dam-reared calves displayed more fear towards humans in a human approach test at 5 and 7 weeks after arrival at the veal farm, and more frequent social behaviours at the veal farm at 9 and 16 weeks of age. In conclusion, it seems that there may be both advantages and disadvantages to keeping veal calves with the dam in terms of welfare in the current system.

Development of an electronic interface for transfer of antimicrobial administration data in dairy farms

Surveillance of antimicrobial administration in livestock production is an important factor in global policies to reduce spreading of antimicrobial resistance. In recent years, many studies have been carried out concerning the usage of antimicrobials in animal production and in some countries recording of antimicrobial quantities dispensed to famers is mandatory. On cattle farms, antimicrobial treatments are recorded for fattening calves under 8 months of age and for fattening cattle older than 8 months in Germany and treatment frequencies are then calculated. However, with the entry into force of Regulation (EU) 2019/6 on 01/28/2022, antimicrobial monitoring will gradually be extended to all animal species and age groups. Therefore, an effective, fast and accurate transfer of data on the use of antimicrobials, especially in the field of livestock farming, into corresponding databases is required to determine the treatment frequencies for the individual animal species or types of use. For this purpose, an electronic interface was programmed to transfer the data on antimicrobial use in dairy cattle farms from a herd management software program directly into a database. To test the practicability and effectiveness of this interface, 10 dairy cattle farms from Saxony were initially selected. Based on an in-depth analysis of the treatment frequencies of antimicrobial administration of 7 different age groups of animals after a two-year observation period, the functionality of the electronic interface could be established. The greatest potential for reduction of antimicrobials is in newborn calves, as they represent the age group with the highest treatment frequency.

Individual antimicrobial treatments in veal calves: Effect on the net carcasses weight at the slaughterhouse and relationship with the serostatus of the calves upon arrival to the fattening unit

In recent years, the scientific community, institutions, and public opinion have shown a growing awareness towards the problem of antimicrobial resistance. Guidelines from the European Union aim at significantly reducing (even avoiding) the antimicrobial use for prophylactic and metaphylactic purposes in veterinary medicine and this represents an important issue for several intensive farming systems, such as the veal industry. This retrospective observational cohort study analyzed net carcass weight data at the slaughter of 618 veal calves belonging to 6 batches of animals fattened in an Italian commercial farm according to the number of individual antimicrobial treatments administered during the fattening cycle. Sixty-eight percent (419 animals) of the overall sample of calves received at least one individual antimicrobial treatment due to a disease event during the fattening, and 280 of these (45 % of the overall sample) had more than one treatment. On average, the net carcass weight of calves individually treated more than once was about 10 kg lower than that of untreated calves or treated only once. Moreover, the carcasses of calves that received more than one treatment were 16 times more at risk of being severely penalized in payment at the slaughterhouse due to a net weight below 110 kg than those of untreated calves. Serum analysis data of a subsample of 105 calves belonging to 3 out of the 6 batches collected within 5 days after their arrival to the veal farm identified 3 persistently infected animals by bovine viral diarrhea (BVD) virus and a prevalence of calves with serum immunoglobulin concentration below 7.5 g/L of 37 %. The presence of specific antibodies against infectious bovine rhinotracheitis (IBR) and bovine respiratory syncytial virus (BRSV) and a serum immunoglobulin level above 7.5 g/L at the onset of the fattening were the most important factors associated with a decreased risk of multiple individual antimicrobial treatments (and thus, disease development) or with a delay in disease onset during the fattening, thus leading to better performances at the slaughter. The outcomes of this study suggested that a relationship could exist between calf serostatus upon arrival to the veal farm and the possibility to avoid multiple individual antimicrobial treatments during fattening. Further research is needed to deeply study this association, as such knowledge would allow for planning effective preventing strategies to reduce the antimicrobial use in veal calves.

Cross-sectional study of primary antimicrobial treatment and vaccination coverage in outbreaks of bovine respiratory disease on dairy and beef farms in northern Belgium

BACKGROUND

To what extent veterinarians active in the dairy or beef sector follow the antimicrobial therapy guidelines made available in different European countries for bovine respiratory disease (BRD) outbreaks, and whether differences in therapeutic or preventive preferences for BRD management exist, is currently unknown. Therefore, the objectives of this cross-sectional study were to compare vaccination coverage and primary antimicrobial and anti-inflammatory treatment on dairy, beef and mixed-breed farms in northern Belgium, and determine their compliance with the recommendations made by the Belgian formulary.

METHODS

Information on antimicrobial and anti-inflammatory drug use and vaccination coverage from 190 BRD outbreaks in 180 herds, submitted by 101 veterinarians, was analysed. Multivariable linear probability models, adjusted for clustering at the veterinarian level, were used to determine differences between dairy and beef farms.

RESULTS

Antimicrobials and non-steroidal anti-inflammatory drugs (NSAIDs) were used in 93.5% and 81.7% of the BRD outbreaks, respectively. First-line antimicrobials were used as primary treatment in only 42.3%, 50.9% and 38.6% of dairy, beef and mixed-breed farms, respectively. Significant differences (p < 0.05) were observed between dairy and beef farms in terms of use of long-acting macrolides (-17.2 percentage points [pp]; 95% confidence interval [CI]: -31.9, -2.5), steroidal anti-inflammatory drugs (15.2 pp; CI: 0.5, 29.8) and vaccination coverage (bovine respiratory syncytial virus, parainfluenza virus type 3 [33.1 pp; Cl: 15.7-50.6] and Mannheimia haemolytica [23.1 pp; Cl: 3.4-39.8]).

LIMITATIONS

The herds that participated in this study were likely among the more motivated regarding BRD control. As such, the information on vaccination coverage is likely not entirely representative of herds in the study area. Interpretation is further complicated by the fact that vaccinated herds were potentially less likely to face a BRD outbreak and therefore participate in the current study.

CONCLUSION

This study reveals differences in the primary use of (N)SAIDs, type of antimicrobials used and vaccination coverage on beef and dairy farms in the study region, and also differences in the appropriateness of antimicrobial selection based on the Belgian formulary.

Respiratory pathogens in veal calves: Inventory of circulating pathogens

In the veal industry in The Netherlands, each year around 1.2 million "white" veal calves are produced on around 1100 farms. Bovine respiratory disease (BRD) causes serious health issues in these calves, also resulting in high usage of antimicrobials. To reduce antimicrobial usage, a more targeted treatment regime is needed, for which it is necessary to identify the causative agent. This study aimed at determining associations between pathogens and clinical disease, between prevalence of pathogens and BRD outbreaks, and BRD and performance. A cohort study was conducted involving ten veal farms, in which calf respiratory health was evaluated for the first 12 weeks. Whenever there was an outbreak of BRD, as determined by the farm veterinary surgeon, samples were taken from diseased and control calves through broncho-alveolar lavage. From these samples a broad spectrum of micro-organisms were isolated. Performance data were also collected. A total of 23 outbreaks happened during the 12 week study period, mostly in the first six weeks. BRD associated pathogens found were: BHV1, BPI3V, BRSV, BVDV, Pasteurella multocida, Mannheimia haemolytica, Trueperella pyogenes, Histophilus somni, Mycoplasma bovis, Mycoplasma bovirhinis and Mycoplasma dispar. For most BRD associated pathogens, there was no clear association between presence or prevalence of the micro-organisms and clinical issues. Only T. pyogenes (7.4% in healthy, 14.6% in diseased calves, p 0.013), M. bovis (37.6% and 63.2% respectively, p 0.001) and BVDV (9.9% and 16.9% respectively, p 0.03) were found more often in diseased animals. BPI3V was found in a few early outbreaks, which might suggest involvement in early outbreaks. It appears to be difficult to associate specific pathogens to outbreaks at the species level. BRD is the major reason for treatment with antimicrobials. More specific knowledge about the association between pathogens and health/disease could help to reduce antimicrobial use.

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 Antimicrobial Stewardship Training on Calf Producers’ Knowledge, Treatment Behaviors and Quantified Antimicrobial Use

The judicious use of antimicrobials on farms is necessary to mitigate the development of antimicrobial-resistant pathogens that compromise human and animal health. On livestock farms, veterinarians prescribe and dispense antimicrobials, but producers use rapid judgements of disease severity to make routine decisions on the initiation of empirical antimicrobial therapy. Therefore, the knowledge and skills required to accurately diagnose treatable bacterial infections is necessary for optimal antimicrobial stewardship. Veal calves often undergo stressors and environmental exposures that increase calves’ risk of bacterial infections, and antimicrobials are sometimes necessary to ensure their health. The objective of this trial was to measure the impact of antimicrobial stewardship training on calf producers’ knowledge of antimicrobial stewardship, accuracy of identifying calves for treatment, and quantified antimicrobial use. Eight farms were evenly allocated into either intervention or control groups. Training resulted in both higher scores on assessments and higher sensitivity for detecting cases that required antimicrobial therapy relative to a veterinarian. Importantly, there was a 50% reduction in the antimicrobial dosing rate among intervention farms relative to control farms. Antimicrobial stewardship training among calf producers was effective at changing producers’ behaviors and reducing antimicrobial use.

Changes in Fecal Carriage of Extended-Spectrum β-Lactamase Producing Enterobacterales in Dutch Veal Calves by Clonal Spread of Klebsiella pneumoniae

This study aimed to characterize the changes in fecal carriage of Extended-Spectrum β-Lactamase (ESBL) producing Enterobacterales (ESBL-PE) in a single Dutch veal calves. During the rearing period at the Dutch veal farm, a decrease in fecal carriage of cefotaxime-resistant Escherichia coli isolates was observed after 2 weeks at the veal farm, while an increase of cefotaxime-resistant Klebsiella pneumoniae isolates was demonstrated. E. coli and K. pneumoniae were isolated from rectal swabs collected from 110 veal calves in week 2, 6, 10, 18, and 24 after their arrival at the farm. ESBL-PE isolates were selectively cultured and identified by MALDI-TOF. ESBL genes were characterized by RT-PCR, PCRs, and amplicon sequencing. A total of 80 E. coli and 174 K. pneumoniae strains were isolated from 104 out of 110 veal calves. The prevalence of ESBL-E. coli decreased from week 2 (61%) to week 6 (7%), while an unexpected increase in ESBL-K. pneumoniae colonization was detected in week 6 (80%). The predominant ESBL genes detected in E. coli isolates were bla_CTX-M-15 and the non-ESBL gene bla_TEM-1a, while in K. pneumoniae bla_CTX-M-14 gene was detected in all isolates. Four cefotaxime-resistant K. pneumoniae isolates were randomly selected and characterized in deep by transformation, PCR-based replicon typing, and whole-genome sequencing (WGS). The clonal relatedness of a subgroup of nine animals carrying K. pneumoniae ESBL genes was investigated by Multi Locus sequence typing (MLST). In four ESBL-K. pneumoniae isolates, bla_CTX-M-14 was located on IncFII_K and IncFII_NK plasmid replicons and the isolates were multi-drug resistant (MDR). MLST demonstrated a clonal spread of ESBL-K. pneumoniae ST107. To the best of our knowledge, this is the first study to report a change in fecal carriage of ESBL-PE over time in the same veal calf during the rearing period.

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.

Preparing Male Dairy Calves for the Veal and Dairy Beef Industry

Surplus male dairy calves experience significant health challenges after arrival at the veal and dairy beef facilities. To curb these challenges, the engagement of multiple stakeholders is needed starting with improved care on some dairy farms and better management of transportation. Differing management strategies are also needed if calves arrive at veal and dairy beef facilities under poor condition.

Effect of Farm Management Practices on Morbidity and Antibiotic Usage on Calf Rearing Farms

Antimicrobial resistance has been recognized as one of the top health threats to human society. Abundant use of antibiotics in both humans and animals has led to ever-increasing antibiotic resistance in bacteria. In food production, decreasing morbidity in beef herds would be an effective way to reduce the use of antibiotics. The objective of this retrospective observational study was to determine overall morbidity on calf rearing farms and to identify associated risk factors. Data were collected by questionnaire, meat companies’ databases and the national cattle register for 28,228 calves transported to 87 calf rearing farms. All medications given to these calves were retrospectively followed for 180 days from calf arrival to the farm. In total, 34,532 parenteral antibiotic medications were administered to the 28,228 study calves (122.3%), and 17,180 calves (60.9%) were medicated with antibiotics at least once during the follow-up. Higher numbers of calves transported to the same farm and larger age variation in calves in the same arrival batch were both associated with increased morbidity. In contrast, higher arrival age of individual calves was associated with decreased morbidity. Our study identifies several factors to consider in decreasing morbidity and antibiotic usage on calf rearing farms.

Randomized field trial comparing the efficacy of florfenicol and oxytetracycline in a natural outbreak of calf pneumonia using lung reaeration as a cure criterion

Background

Respiratory infections are the main indication for antimicrobial use in calves. Optimal treatment duration currently is unknown, but shorter duration would likely decrease selection for antimicrobial resistance.

Hypothesis/Objectives

Determine differences in cure rate and healing time between animals treated with florfenicol and oxytetracycline in a natural outbreak of respiratory disease using reaeration observed on thoracic ultrasound examination as healing criterion.

Animals

Commercial farm housing 130, 3 to 9 month old Belgian blue beef calves.

Methods

Randomized clinical trial during an outbreak of respiratory disease. Metaphylactic treatment was initiated, randomly treating animals with either florfenicol or oxytetracycline. Ultrasonographic follow‐up was done the first day and every other day for a 14‐day period. At the individual animal level, treatment was discontinued when reaeration of the lungs occurred. Differences in cure rate and healing time were determined.

Results

Of the 130 animals studied, 67.7% developed a lung consolidation ≥0.5 cm. The mean ultrasonographic healing time was 2.5 days in the florfenicol group compared to 3.1 days in the oxytetracycline group (P = .04). After single treatment, 80.6% and 60.3% had no consolidations in the florfenicol and oxytetracycline groups, respectively (P = .01). A Mycoplasma bovis strain was genetically and phenotypically determined to be susceptible to both antimicrobials.

Conclusions and Clinical Importance

Ultrasonographic lung reaeration shows potential as a cure criterion to rationalize antimicrobial use for outbreaks of pneumonia. In our study, florfenicol resulted in a faster cure and higher reduction in antimicrobial usage than did oxytetracycline.

Factors associated with antimicrobial use in pig and veal calf farms in the Netherlands: A multi-method longitudinal data analysis

Minimizing antimicrobial use (AMU) in livestock is needed to control antimicrobial resistance (AMR). In the Netherlands, the livestock sector reduced AMU by almost 70 % since 2009, but this reduction stagnated in recent years. With only therapeutic AMU allowed, it is clear that besides socio-economic and behavioral factors, also the farm technical characteristics influence the conditions under which farmers need AMU. These characteristics pertain to farm management, including biosecurity, vaccination schemes, nutrition, micro-climate and husbandry practices. Identifying farm-related risk factors for AMU is needed to control AMR in a sustainable and pragmatic way. This need, often concerns the overall contribution of seemingly related (rather than individualized) factors. Here, risk factors for AMU in pig and calf farms were determined using two approaches: a typical risk factor analysis based on generalized estimating equations (GEEs) or hierarchical mixed-effects models and a multiblock partial least-squares regression analysis. These methods were applied to longitudinal data from two previous studies, i.e. a panel study and an intervention study involving 36 multiplier pig farms and 51 veal calf farms in the Netherlands, respectively. The multiblock analysis allowed us to quantify the importance of each factor and their respective block (i.e. farm management domain). For pigs, factors related to internal biosecurity had the highest impact on AMU, while for calves, these were mainly related to micro-climate. Structural characteristics, such as farm size and production type, followed in importance for both sectors. While both methods provided similar outcomes, the multiblock approach provided further insights by grouping and comparing factors believed to be inter-related.

Large-size fattening calves' lots fed with automatic milk feeders may have an increased risk for Mycoplasma bovis infection spread and for antibiotic use

Bovine respiratory disease is the leading user of antibiotics (AB) in calf production. Mycoplasma (M.) bovis could lead to greater use of AB as it is a persistent and AB resistant causative agent for respiratory diseases. Two cross-sectional studies were set up to assess the effects of lot size and feeding system on M. bovis infection and the effects of M. bovis seroconversion, lot size and feeding system on AB use in calves' feedlots. Twenty-six lots in 22 fattening farms were monitored for 41-81 days, from all-in entry of calves until three consecutive weeks without using any collective antibiotics. M. bovis spread was estimated by measuring seroconversion at entry and at the end of study period in 10-15 calves randomly sampled in each lot. All AB treatments used in the meanwhile were recorded. The lots were selected according to feeding system, i.e. individual bucket (n = 7) vs. automated milk feeder (AMF, n = 19), and lot size (30-519 calves), less than 50 calves (n = 9) vs. more than 50 calves (n = 17). Statistical analysis was performed using multivariable generalised linear models with fattening farms as random effect. M. bovis spread increased with lot size (odds ratio (OR) 2.9[1.4; 5.8] per two-fold increase in lot size). This proportion of seroconverted calves was lower in bucket-fed lots compared to lots fed with the AMF using a shared nipple (OR = 0.03[0.003; 0.41]). The main risk factor for AB use was the lot size, with an increase of 1.5[0.94; 1.98] treatments per two-fold increase in lot size. For same size lots, the use of bucket can decrease AB consumption by up to 1.03[-2.18; 0.14] treatments per calf compared to AMF. Analysis of the association between seroconversion to M. bovis and AB use was inconclusive. We found that bucket feeding in small-size lots, i.e. up to a maximum of 50 calves in the same space, limits seroconversion to M. bovis and enables lower use of AB in veal calf production.

Prevalence of BRD-Related Viral Pathogens in the Upper Respiratory Tract of Swiss Veal Calves

The prevention of bovine respiratory disease is important, as it may lead to impaired welfare, economic losses, and considerable antimicrobial use, which can be associated with antimicrobial resistance. The aim of this study was to describe the prevalence of respiratory viruses and to identify risk factors for their occurrence. A convenience sample of 764 deep nasopharyngeal swab samples from veal calves was screened by PCR for bovine respiratory syncytial virus (BRSV), bovine parainfluenza-3 virus (BPI3V), bovine coronavirus (BCoV), influenza D virus (IDV), and influenza C virus (ICV). The following prevalence rates were observed: BRSV, 2.1%; BPI3V, 3.3%; BCoV, 53.5%; IDV, 4.1%; ICV, 0%. Logistic mixed regression models were built for BCoV to explore associations with calf management and housing. Positive swab samples were more frequent in younger calves than older calves (>100 days; p < 0.001). The probability of detecting BCoV increased with increasing group size in young calves. Findings from this study suggested that young calves should be fattened in small groups to limit the risk of occurrence of BCoV, although an extended spectrum of risk factors for viral associated respiratory disorders such as nutritional aspects should be considered in future studies.

Effect of farm and animal-level factors on youngstock mortality and growth on calf rearing farms

Both calf mortality and daily weight gain have a crucial impact on profitability of calf rearing farms. In addition, high calf mortality rates represent an animal welfare problem. Mortality rates on calf rearing farms have been reported in several studies in different countries, but scant data regarding daily weight gain of the calves are available. The objectives of this observational retrospective study were to determine the average mortality and daily weight gain of calves and youngstock on Finnish calf rearing farms and to identify factors associated with these production parameters. National cattle register and national herd health register databases together with meat companies' databases were used to collect weight, age, breed, medication, and origin farm data for 28 228 calves transported to the 87 calf rearing farms between 1 January and 1 October 2016. A telephone questionnaire was completed by selected farms to collect management and farm-specific data. Calves were retrospectively followed for maximum 180 days since arrival to the farm. Average arrival age of the calves were 24 days (SD 14). Average calf mortality on Finnish calf rearing farms was 4.5 %. Mortality was 5.3 % on fattening farms buying milk calves, 4.6 % on specialized calf rearing farms, and 2.5 % on fattening farms buying weaned calves. Size of the calf rearing farms varied, being smallest on fattening farms for weaned calves and largest on specialized calf rearing farms. Average daily gain of the study calves was 1.074 kg/day (SD 0.166). Multilevel mixed effects logistic and linear regression models, where herd and calf batch were used as random effects, were generated to study calf level mortality and daily gain, respectively. Activities preventing transmission of pathogens between arrival batches and different age groups of animals, including application of the all in/all out principle and proper washing and disinfection of compartments for milk feeding calves between arrival batches, were associated with lower mortality and increased daily gain. In addition, higher arrival age was associated with lower mortality during the rearing period and relatively higher arrival age of the calf, compared to other calf in a same arrival batch, was associated with higher daily gain. By contrast, increased number of individual medications during the rearing period was associated with both increased mortality and decreased daily gain. There was no significant difference in mortality between farm types. Current study highlights several factors that can be affected in future to further develop the beef production chain.

The effect of neomycin inclusion in milk replacer on the health, growth, and performance of male Holstein calves during preweaning

The prophylactic use of oral antimicrobials, such as neomycin, in milk replacer (MR) or whole milk is a common practice in calf-rearing that is thought to aid in preventing disease. Heavy reliance on antimicrobials is of concern not only because of the development of antimicrobial resistance, but also because of the potentially negative effects on health. The objective of this study was to investigate the effects of neomycin on calf health and growth performance. One hundred and sixty calves (approximately 3-10 d of age), distributed across 2 experimental periods, were stratified by body weight (BW) and serum total protein, and assigned to 1 of 3 treatments: control (CON; nonmedicated MR, n = 60), short-term antibiotic (ST; neomycin mixed in MR from d 1-14, n = 50), or long-term antibiotic (LT; neomycin in ​MR from d 1-28, n = 50). Arrival BW (47.69 ± 0.87 kg) and serum total protein (5.67 ± 0.09 g/dL) were not different between treatment groups. Neomycin in ST and LT was dosed in MR at a rate of 20 mg/kg of BW and was adjusted weekly according to BW. Calf BW was measured weekly for 49 d, and health indicators (fecal score, attitude score, respiratory score, and rectal temperature), MR intake, starter intake, and the use of additional electrolytes and antimicrobials were recorded daily. Calves in the CON group experienced a higher proportion of days with diarrhea (20.32 ± 0.02%) compared with ST (14.70 ± 0.02%) or LT (13.80 ± 0.02%) calves, as well as longer bouts of diarrhea (7.45 ± 0.38 d, 5.69 ± 0.46 d, and 5.62 ± 0.45 d for CON, ST, and LT calves, respectively). Calves in the CON group also experienced higher fecal scores (score of 0.64 ± 0.04) than ST (score of 0.53 ± 0.04) or LT (score of 0.49 ± 0.04) calves, especially at d 7. However, no differences were observed in other health-related measures. The time to reach first diarrhea and first respiratory illness was not different between treatments, nor was the time to recover from respiratory illness. The time to intervention with additional electrolytes or antimicrobials was not different between treatment groups. Furthermore, growth performance, feed intake, and feed conversion ratio were not different. No differences were found when comparing ST and LT, except in the defined daily dose of total antimicrobials received. Calves in the LT group received a higher overall dose than ST calves, and both ST and LT calves received a higher dose than CON calves, which received no prophylactic antimicrobials. Given that there were no differences in performance variables and no additional health benefits aside from reduced fecal scores in calves fed neomycin, current practices involving the use of antimicrobials on dairy and veal operations need to be considered more prudently.

Antimicrobial use and resistance in Escherichia coli from healthy food-producing animals in Guadeloupe

Background

Selection pressure exerted by use of antibiotics in both human and veterinary medicine is responsible for increasing antimicrobial resistance (AMR). The objectives of this study were to better understand antimicrobial use in pigs, beef cattle, and poultry on farms on Guadeloupe, French West Indies, and to acquire data on AMR in Escherichia coli in these food-producing animals. A cross-sectional survey was conducted at 45 farms on Guadeloupe, and practical use of antimicrobials was documented in declarative interviews between March and July 2018. A total of 216 fecal samples were collected between January 2018 and May 2019, comprising 124 from pigs, 75 from beef cattle, and 17 from poultry litter. E. coli isolates were obtained for further testing by isolation and identification from field samples. Antimicrobial susceptibility testing and screening for bla_CTX-M, bla_TEM, tetA, and tetB resistance genes by polymerase chain reaction on extracted genomic DNA were performed.

Results

The study showed rational use of antimicrobials, consisting of occasional use for curative treatment by veterinary prescription. Tetracycline was the most commonly used antimicrobial, but its use was not correlated to E. coli resistance. Extended-spectrum β-lactamase (ESBL) E. coli isolates were detected in 7.3% of pigs, 14.7% of beef cattle, and 35.3% of poultry. bla_CTX-M-1 was the predominant gene found in ESBL-E. coli isolates (68.8%), followed by bla_CTX-M-15 (31.3%).

Conclusion

Despite rational use of antimicrobials, the rate of ESBL-E. coli in food-producing animals in Guadeloupe, although moderate, is a concern. Further studies are in progress to better define the genetic background of the ESBL-E. coli isolates.

Graphical abstract

The Welfare of Beef Cattle in the Scientific Literature From 1990 to 2019: A Text Mining Approach

Beef cattle are the third most numerous terrestrial farmed animals worldwide. Factors such as geographical region, animal category, breed, and rearing system pose specific animal welfare challenges that can have an impact on animal and public health. This article uses text mining (TM) and topic analysis (TA) to explore the scientific literature on beef cattle welfare published in English from 1990 to 2019. Our aim was to reveal the main research topics and their evolution over time. Our analysis showed that the three most relevant themes in research since 1990 have to do with calf behaviour and management, efficiency, and environmental sustainability, and the effects of transport and slaughter on meat quality. Topics showing the most marked increase in the number of papers published deal with stakeholders' perceptions and market opportunities for added-value beef products and risk factors for morbidity and mortality, especially in relation to calf health, antimicrobial use, and antimicrobial resistance. The results indicate a particular focus on the welfare of calves, especially in the veal industry. Pain relief during the castration of calves and bulls also featured prominently. Research is also increasingly assessing aspects of beef cattle welfare that are interlinked to meat quality, the social and environmental sustainability of the sector in relation to market opportunities, and public health. The identified topics represent a basic source of information that can be used for further and more detailed analyses (e.g., systematic reviews) focussed on specific research themes or geographical areas.

Comparison of antimicrobial prescription patterns in calves in Switzerland before and after the launch of online guidelines for prudent antimicrobial use

BACKGROUND

The increasing threat of bacterial resistance promotes the need for antibiotic stewardship programs to foster responsible antimicrobial use. Therefore, guidelines for prudent use supported by an online stewardship tool (AntibioticScout.ch) were introduced in Switzerland in December 2016. They recommend (with decreasing preference) a first, second or third line antimicrobial for treatment. The objective of this study was to evaluate antimicrobial prescriptions for Swiss calves before (2016) and after (2018) the launch of these guidelines. Cases of calves with pneumonia, diarrhea and otitis from a university hospital and eight private practices in Switzerland were included. Data on anamnesis, clinical findings, diagnostic work-up and treatment were collected. Type and percentages [95% confidence interval] of antimicrobial prescriptions were compared between 2016 and 2018.

RESULTS

Of the total number of calves, 88.2% [85.4-90.6] in 2016 (n = 625) and 88.4% [85.7-90.7] in 2018 (n = 655) were treated with antibiotics. The use of highest priority critically important antimicrobials (HPCIAs) decreased from 52.7% [48.6-56.9] in 2016 to 38.0% [34.2-41.9] in 2018; this decrease was found at the university hospital and in private practice and in cases with pneumonia and diarrhea. Particularly the use of fluoroquinolones decreased (2016: 43.1% [39.2-47.2]; 2018: 31.1% [27.6-34.8]). Overall, the number of first line treatments increased from 12.8% [10.4-15.6] in 2016 to 20.2% [17.3-23.4] in 2018. In cases of pneumonia, first line treatments increased (2016: 15.3% [11.6-19.9]; 2018: 26.5% [21.8-31.9]) and third line treatments decreased (2016: 43.5% [38.0-49.3]; 2018: 27.9% [23.1-33.3]); this was seen at the university hospital, whereas in private practice only a decrease of third line treatments was observed. In cases of diarrhea, more second line at the expense of unlisted antimicrobials were prescribed at the university hospital in 2018. Antimicrobial treatment of calves with otitis did not change from 2016 to 2018.

CONCLUSIONS

After the introduction of AntibioticScout.ch, more prudent use was observed in the treatment of calves with pneumonia and diarrhea as less HPCIAs, particularly fluoroquinolones, and more first line antimicrobials were prescribed. However, the overall frequency of antimicrobial treatment did not change and the use of HPCIAs was still common in 2018, especially in private practices. Therefore, further antimicrobial stewardship activities are necessary.

Hot topic: Health and welfare challenges in the marketing of male dairy calves-Findings and consensus of an expert consultation

A diverse group of Canadian experts was convened for a focused 2-d discussion on potential health and welfare problems associated with the marketing (i.e., transportation and sale) of male dairy calves. Written notes and audio recording were used to summarize the information provided on transport times and marketing practices. Content analysis was used to develop a consensus statement on concerns, possible solutions, and recommendations to improve male dairy calf marketing. The group noted that calves across all Canadian regions are commonly transported at 3 to 7 d of age and undergo transport for 12 to 24 h or longer depending on the location of their dairy farm of origin. Calves in some regions are marketed almost exclusively through auction markets, whereas others have more direct sales. A need was identified for better criteria for calf fitness for transport, maintaining farm biosecurity, reducing the use of antimicrobial therapy in calf production, and improving education for farmers and veterinarians on the importance of neonatal care for male dairy calves before transportation. Experts noted that major changes in male dairy calf marketing will be required to comply with amendments to the federal Health of Animals Regulations (Part XII) on animal transportation; collaborative effort will be needed to safeguard animal health and welfare as this transition is made.

Transition Pathways Toward the Prudent Use of Antimicrobials: The Case of Free-Range Broiler Farmers in France

Reducing antimicrobial use (AMU) on farms is key for controlling the rise of resistant bacteria that have the potential capacity to infect humans via direct animal contact or via the food chain or the environment. To reduce AMU, antimicrobials must be used in a prudent and rational manner. Extensive efforts have been made recently to identify the cognitive and behavioral barriers to the appropriate use of antimicrobials by various livestock sector stakeholders. However, most studies carried out thus far have only partly captured the dynamic and systemic dimension of the processes involved in changes of practices related to AMU on farms. To shed light on the transition pathways implemented to reduce AMU, a qualitative study was conducted in France based on 28 semi-structured interviews with farmers, technicians and veterinarians from the free-range broiler production sector. Based on the thematic analysis of verbatims, we identified technical improvements which are key contributors to reduced AMU. We also highlighted some gaps in knowledge regarding AMU and antimicrobial resistance. We found that, rather than individual motivations alone, the extent to which farmers are embedded in collective organizations is decisive for changes in practices, and downstream operators (distributors and slaughterers) play a key role in the beginning of AMU transition pathways. As a result, we show that change in AMU requires a global rethinking of the overall socio-technical system rather than modifications of a single element in a farming system. Our results also highlight that transition pathways toward reduced AMU cannot just rely on trigger events, but also involves medium or long-term processes, with actors' experiences and practices being modified on an incremental basis over time. Our study sheds light on the need for multi and trans-disciplinary research involving the social sciences to analyze interactions between stakeholders and the collective actions implemented to tackle the challenge of AMU reduction.

Welfare Assessment in Calves Fattened According to the "Outdoor Veal Calf" Concept and in Conventional Veal Fattening Operations in Switzerland

Simple Summary

Antimicrobial use in humans and animals leads to the selection of resistant bacteria, a serious threat to human and animal health, as such bacteria can lead to treatment failure and death. With the “outdoor veal calf” concept, a novel calf fattening system was developed that allows for reducing antimicrobial use by 80% through improvements in management and housing, such as health check before purchase, short transport, vaccination, quarantine in individual hutches, and fattening in small groups in a roofed, straw-bedded paddock with a group hutch for shelter. In that system, veal calves spend their entire lives outdoors in the fresh air. In our study, we wanted to make sure that the observed reduction in antimicrobial treatments was not achieved at the cost of animal welfare, i.e., that sick animals were not left without treatment in order to obtain better figures for treatment reduction. Our results show that calves in the “outdoor veal calf” system had fewer signs of respiratory and digestive diseases than control calves and that their lungs had fewer lesions of pneumonia than controls after slaughter. Thus, not only was antimicrobial use drastically reduced, but calf health was really improved in the new “outdoor veal calf” system.

Abstract

The “outdoor veal calf” system was developed to encounter the demand for a veal fattening system that allows for reducing antimicrobial use without impairing animal welfare. Management improvements including direct purchase, short transportation, vaccination, three-week quarantine in individual hutches, and open-air housing in small groups in a roofed, straw-bedded paddock with a group hutch were implemented in a prospective intervention study (1905 calves, 19 intervention and 19 control farms, over one year): antimicrobial use was five times lower in "outdoor veal" farms compared to control farms (p < 0.001), but it was crucial to ensure that antimicrobial treatment reduction was not associated with decreased animal welfare, i.e., that sick animals were not left untreated. Welfare was assessed monthly on the farms, and organs of 339 calves were examined after slaughter. Cough and nasal discharge were observed significantly (p ≤ 0.05) less often in intervention than in control farms, mortality (3.1% vs. 6.3%, p = 0.020) and lung lesion prevalence (26% vs. 46%, p < 0.001) were lower; no group difference was seen in abomasal lesion prevalence (65% vs. 72%). Thus, besides reduced antimicrobial use, calf health and welfare were improved in "outdoor veal calf" farms in comparison to traditional operations.

Phylogenomic analysis of Mycoplasma bovis from Belgian veal, dairy and beef herds

M. bovis is one of the leading causes of respiratory disease and antimicrobial use in cattle. The pathogen is widespread in different cattle industries worldwide, but highest prevalence is found in the veal industry. Knowledge on M. bovis strain distribution over the dairy, beef and veal industries is crucial for the design of effective control and prevention programs, but currently undocumented. Therefore, the present study evaluated the molecular epidemiology and genetic relatedness of M. bovis isolates obtained from Belgian beef, dairy and veal farms, and how these relate to M. bovis strains obtained worldwide. Full genomes of one hundred Belgian M. bovis isolates collected over a 5-year period (2014–2019), obtained from 27 dairy, 38 beef and 29 veal farms, were sequenced by long-read nanopore sequencing. Consensus sequences were used to generate a phylogenetic tree in order to associate genetic clusters with cattle sector, geographical area and year of isolation. The phylogenetic analysis of the Belgian M. bovis isolates resulted in 5 major clusters and 1 outlier. No sector-specific M. bovis clustering was identified. On a world scale, Belgian isolates clustered with Israeli, European and American strains. Different M. bovis clusters circulated for at least 1.5 consecutive years throughout the country, affecting all observed industries. Therefore, the high prevalence in the veal industry is more likely the consequence of frequent purchase from the dairy and beef industry, than that a reservoir of veal specific strains on farm would exist. These results emphasize the importance of biosecurity in M. bovis control and prevention.

Veterinary drug administration in German veal calves: An exploratory study on retrospective data

The aim of this cross-sectional study was to characterise the usage of antibiotic and non-antibiotic drugs with a withdrawal period in German veal calves in more detail. In Germany, the documentation of the usage of veterinary medicinal products in food producing animals is mandatory. In the German monitoring system antibiotic use in calves under the age of eight months is recorded irrespective of the production type and only some basic measures (50 % and 75 % percentiles of the entire distributions of the treatment frequencies) are published regularly. Within this study 57 farms were included contributing data of 169 veal calf groups with a total of 91,196 individual calves. To assess the drug use the treatment frequency (TF) was calculated. Most treatments were applied in the first weeks after arrival at the farm against respiratory and gastrointestinal disorders, accounting for 65.2 % and 28.6 % of the TF, respectively. Antibiotics account for 91 % of the TF. The antibiotics used most frequently were tetracyclines (35.6 %), beta-lactams (21.9 %), macrolides (12.7 %), sulphonamides (6.0 %) and trimethoprimes (5.3 %). Tetracyclines and polypeptides were administered as group treatments in more than half of the recorded applications. The number of antibiotic group treatments decreased considerably from the first to the second half of the fattening period. Logistic regression analyses revealed no statistically significant association between TF and groups size or mortality. Nevertheless, the results indicate a negative associated between TF and mortality. Concerning non-antibiotics mainly iron compounds, arylpropionic acids, mucolytics and avermectines were applied, accounting for about 5 % of the total TF. The present study provides basic data on antibiotic and non-antibiotic use in German veal calf production.

Stakeholders' perceptions of the challenges to improving calf health and reducing antimicrobial use in Swiss veal production

Large quantities of antimicrobials are used in Swiss veal production. To develop strategies to reduce antimicrobial use, it is important to understand how stakeholders along the veal production chain perceive the current situation and to find the key issues that challenge them about calf health management and antimicrobial use. However, there has been insufficient research into the individual contexts of the supply chain actors, and the central themes that they perceive to enable or limit their actions remain largely unknown. The aim of this study is to investigate the perceptions of the current situation of the Swiss veal production system, in terms of calf health management and antimicrobial use held by industry stakeholders, i.e. dairy farmers, veal producers, traders, slaughterhouse managers, advisors and veterinarians. Qualitative interviews were conducted with 27 respondents and analyzed using content analysis. The results show that stakeholders are aware of the current need to minimize resistance development and the related risks for public health by reducing antimicrobial use. The main reason for high antimicrobial use was nominated as the practice of purchasing calves from many different dairy farms and bringing them together in large groups at a young age, which exposes them to a variety of pathogens that their still developing immune systems are not able to cope with. To prevent and combat infectious diseases which are a frequent consequence of this practice, antimicrobial group treatments are commonly administered, which significantly raises the total amount of antimicrobials used. Group level treatments with antimicrobials were associated directly with the large-scale veal farming system, which uses excess calves from specialized dairy farms, and which the respondents perceive to cause financial pressure and mutual dependencies among participants. In addition, disunity between actors was perceived as a further challenge to find strategies for the reduction of antimicrobial use. The respondents suggested downscaling the production system so that calves can be treated individually but conceded that the current system may be very difficult to change, so also suggested various improvement measures within the existing system. The results of this study provide a basis for further research to investigate possible interventions that could considerably reduce antimicrobial use in veal production.

Effects of the novel concept 'outdoor veal calf' on antimicrobial use, mortality and weight gain in Switzerland

The aim of the intervention study 'outdoor veal calf' was to evaluate a novel concept for calf fattening which aimed at reducing antimicrobial use without compromising animal health. Management practices such as commingling of calves from multiple birth farms, crowding, and suboptimal barn climate are responsible for high antimicrobial use and mortality in the veal calf population. The risk of selecting bacteria resistant to antimicrobials and of economic losses is accordingly elevated. The 'outdoor veal calf' concept, implemented in nineteen intervention farms (IF), is based on three main measures: 1. purchased calves are transported directly from neighboring birth farms to the fattening facility instead of commingling calves in livestock dealer trucks; 2. each calf is vaccinated against pneumonia after arrival and completes a three-week quarantine in an individual hutch; and 3. the calves spend the rest of the fattening period in outdoor hutches in groups not exceeding 10 calves. The covered and bedded paddock and the group hutches provide shelter from cold weather and direct sunshine, constant access to fresh air is warranted. Nineteen conventional calf fattening operations of similar size served as controls (CF). Every farm was visited once a month for a one-year period, and data regarding animal health, treatments, and production parameters were collected. Treatment intensity was assessed by use of the defined daily dose method (TI_DDD in days per animal year), and calf mortality and daily weight gain were recorded in both farm groups. Mean TI_DDD was 5.3-fold lower in IF compared to CF (5.9 ± 6.5 vs. 31.5 ± 27.4 days per animal year; p < 0.001). Mortality was 2.1-fold lower in IF than in CF (3.1% ± 2.3 vs. 6.3 % ± 4.9; p = 0.020). Average daily gain did not differ between groups (1.29 ± 0.17 kg/day in IF vs. 1.35 ± 0.16 kg/day in CF; p = 0.244). A drastic reduction in antimicrobial use and mortality was achieved in the novel 'outdoor veal calf' system without compromising animal health. The principles of risk reduction used in designing the system can be used to improve management and animal health, decrease the need for antimicrobial treatments and thus selection pressure on bacteria in veal operations.

Short communication: Risk factors identified at arrival associated with average daily gain at a grain-fed veal facility: A prospective single cohort study

The primary objective of this prospective cohort study was to identify factors evaluated upon arrival at a grain-fed veal facility that were associated with increased growth. A secondary objective was to determine if the factors associated with average daily gain (ADG) varied between the pre- and postweaning periods. Calves were visually assessed and scored using a standardized health scoring system immediately upon arrival. They were also weighed and vaccinated, and had blood drawn from their jugular vein to determine their serum total protein level. Weights were taken on d 49 and 78 after arrival and were used to calculate ADG. Three mixed linear regression models were created to determine factors associated with ADG from 0 to 49 d after arrival, 0 to 78 d after arrival, and 49 to 78 d after arrival. A total of 998 calves were evaluated and weighed upon arrival; 636 and 915 of those calves were weighed at d 49 and d 78, respectively. Mean ADG were 610 g/d from 0 to 49 d after arrival, 860 g/d from 0 to 78 d after arrival, and 1,240 g/d from 49 to 78 d after arrival. In the model evaluating growth from 0 to 49 d, calves arriving at the facility with a higher body mass index (BMI) gained more weight per day than calves that arrived with a lower BMI. If calves arrived in the spring, they gained 201 g/d more than calves that arrived in the winter. For the period following weaning (d 49 to 78), BMI was also associated with growth. For every additional 1 g/cm² increase in BMI at arrival, calves gained an additional 1.55 g/d from d 49 to 78. Growth from arrival to d 78 was affected solely by BMI. For every 1 g/cm² increase in BMI at arrival, calves gained 1.23 g/d more during the entire observation period. Body mass index and season at arrival affected growth through the initial period at a grain-fed veal facility. Producers should consider these factors, especially BMI, when purchasing calves to maximize the calves' growth potential.

Short communication: Herd-level analysis of antimicrobial use and mortality in veal calves: Do herds with low usage face higher mortality?

The veal calf sector fears that a too-rapid and large decrease in antimicrobial use (AMU) as demanded by European authorities would increase mortality, causing economic and welfare issues. To determine whether this concern is justified, the relationship between AMU (total and different classes) and mortality in dairy-type white veal calves, managed by 2 large veal companies, was explored. A retrospective cohort study was performed on electronically collected antimicrobial consumption and mortality data from the largest Belgian veal practice during the period 2014 to 2016. Mixed linear [mortality (%) as continuous outcome] and generalized linear mixed models with binary outcome for event and trial approach were built to identify factors associated with mortality. Data consisted of 76 production cycles from 29 farms managed by 2 veal companies (1 and 2) and covering 45,001 calves. Average AMU was 30.1 ± 10.4 defined daily doses for animals per year (± standard deviation) and was higher in veal company 2 than in veal company 1 (35.9 ± 9.3 and 22.4 ± 5.7 defined daily doses for animals per year, respectively). In contrast, mean mortality was lower in veal company 2 (2.3 ± 1.4%) than in veal company 1 (4.1 ± 1.4%). Both models showed a positive association between AMU and mortality in veal company 1 and no association in veal company 2. The final linear model identified increasing herd size and the use of third- or fourth-generation cephalosporins as risk factors for mortality and the use of long-acting macrolides as a protective factor. The final logistic model identified an increased mortality risk with increased use of third- or fourth-generation cephalosporins and sulfonamides-trimethoprim and decreased mortality when using long-acting macrolides. Based on these data, at the current levels of AMU in Belgian veal calves, an increase in mortality when reducing AMU could not be evidenced. Differences in herd size and factors other than AMU likely better explain why one veal company faces almost double the mortality of another one. Abandoning the use of long-acting macrolides might have negative consequences for mortality under the current state of the industry. The most ethical way to further reduce AMU in veal calves is likely simultaneously monitoring AMU and animal welfare parameters, starting with, but not limited to, mortality.

Biosecurity practices in Belgian veal calf farming: Level of implementation, attitudes, strengths, weaknesses and constraints

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Biosecurity awareness among veal farmers was very low.

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On average, veal farms were filled in 11.4 days.

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On average, 124 calves originated from 100 farms of origin.

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No difference in biosecurity level could be found between different veal companies.

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Fundamental changes are needed to improve biosecurity regarding introduction of animals.

The shift from cure toward prevention in veterinary medicine involves the implementation of biosecurity. In cattle farming, the application of biosecurity measures has been described to a limited degree, yet no data on biosecurity on veal farms is available. A high degree of commingling of veal calves from multiple farms causes frequent disease outbreaks, and thereby high antimicrobial usage and increased risk of antimicrobial resistance. Therefore, this study aimed to describe the current implementation of biosecurity on veal farms in Belgium. To this extent, a list of the most important calf diseases (n = 34) was created, and risk factors and related biosecurity measures for these diseases were determined and included in a questionnaire. Herd visits and face-to-face interviews were conducted on 20 randomly selected veal farms, comprising 8.3% of the target population. A categorical principal component and clustering analysis were performed to determine the influence of the veal companies on the farms’ biosecurity level. Awareness of biosecurity was very low among the farmers. All farms used an “all-in, all-out” production system with calves originating from multiple farms without quarantine. On average, farms were filled in 11.4 days (range 2–52). The degree of commingling for these farms was 1.24, meaning that, on average, 124 calves originated from 100 farms. Veterinarians wore farm-specific boots on eight farms (40%) and farm-specific clothes on six farms (30%), while technical advisors wore farm-specific boots on six farms (30%) and farm-specific clothes on four farms (20%). Disinfection footbaths were only used in five farms (25%) despite being present in all farms in the sample. Concerning internal biosecurity, none of the farmers isolated sick animals; only one farmer (5%) had a physically separated hospital pen, and only 11 farmers (55%) both cleaned and disinfected the stables after each production cycle. In most farms, animals were of comparable age. Healthy calves generally remained in the same compartment during the entire production cycle, limiting the risks associated with the movement of animals. No influence of the integrations on the biosecurity level could be determined. It can be concluded that a few biosecurity measures, such as “‘all-in, all-out” and compartmentation, are implemented relatively well, while other measures, such as good cleaning and disinfection and proper entrance measures for visitors and personnel can easily be improved. The improvement of measures regarding the introduction of animals of different origins will require more fundamental changes in the veal industry.

Risk factors identified on arrival associated with morbidity and mortality at a grain-fed veal facility: A prospective, single-cohort study

High levels of morbidity, mortality, and antimicrobial use are common in the veal industry. For the sustainability of the industry, it is important to address these challenges and determine factors that can be used to improve animal health and welfare. The objectives of this prospective observational cohort study were to describe the health status of calves on arrival at a grain-fed veal facility and determine characteristics that were associated with morbidity and mortality. On arrival, the calves were assessed for health abnormalities, weighed, measured for hip height and length from withers to lumbosacral junction, and had blood collected to determine serum total protein level. Body mass index (BMI) was calculated using weight on arrival divided by the sum of the calf's length from withers to lumbosacral junction and hip height. The calves were observed for 77 d after arrival, during which the producer was responsible for recording all antibiotic treatments and mortality. We built Cox proportional hazard models for morbidity and mortality variables. We created 2 morbidity models: 1 for calves that were treated <21 d after arrival at the facility, and 1 for calves that were treated during the 11 wk at the facility. From January to December 2017, 998 calves were evaluated on arrival at the veal rearing facility. A large proportion (68%) were treated with antibiotics in the first 21 d after arrival. The only explanatory variable in the final <21 d morbidity model was BMI: calves with a higher BMI had a lower hazard of being treated for disease in the first 21 d after arrival. A total of 872 calves (87%) were treated at least once over the 11-wk housing period. A calf arriving with a BMI >371.46 g/cm or a serum total protein between 5.8 and 6.2 g/dL had a lower level of morbidity during the observation period. Over the 11-wk housing period, 74 calves (7.5%) died. Calves that arrived at the facility with a fecal score of 2 or a rectal temperature between 38.9 and 39.1°C had a higher hazard of dying; calves that had a BMI of >371 g/cm were less likely to die than calves that had a BMI <330 g/cm. These results point to the importance of assessing calves on arrival at a veal facility as a measure of identifying those at high risk for morbidity and mortality.

Associations between antimicrobial treatment modalities and antimicrobial susceptibility in Pasteurellaceae and E. coli isolated from veal calves under field conditions

Antimicrobial consumption, with bovine respiratory disease as main indication, is higher in the veal calf industry compared to other livestock production branches. The aim of the present study was to investigate possible associations between antimicrobial drug use and resistance in Pasteurellaceae and indicator Escherichia (E.) coli from veal calves under field conditions in a prospective trial. Over a period of one year, nasopharyngeal and rectal swabs were collected from 2587 animals on 12 and 43 farms, respectively. Antimicrobial susceptibility testing was performed on 346 Mannheimia (M.) haemolytica, 1162 Pasteurella (P.) multocida and 2138 E. coli. Drug use was quantified as treatment incidence for each farm based on the used daily dose methodology (TI_UDD), separately for group and individual treatments, and for antimicrobial classes. In multivariable mixed logistic regression analyses, risk factors could be identified for reduced susceptibility to certain antimicrobial classes. Group treatment was generally associated with higher rates of not susceptible (NS) M. haemolytica and P. multocida and non-wildtype (non-WT) E. coli. Individual treatment was associated with less NS and non-WT isolates. Age and entry protocol were important confounders with younger animals showing higher rates of NS and non-WT strains. The present findings suggest that, under field conditions, targeted individual treatment of calves can reduce the development of antimicrobial resistance compared to oral group treatment. For the different microorganisms, risk factors for resistance were partially different. This demonstrates that indicator organisms like E. coli do not necessarily reflect the associations observed in respiratory pathogens.

Saccharomyces cerevisiae boulardii CNCM I-1079 affects health, growth, and fecal microbiota in milk-fed veal calves

The objective of this study was to investigate the effect of one specific strain of yeast, Saccharomyces cerevisiae boulardii CNCM I-1079 (SCB), on the growth performance, health, and fecal bacterial profile of veal calves. A total of 84 animals were enrolled in an experiment at a commercial veal farm for a total of 7 wk. Calves were fed twice a day with a milk replacer meal during the entire experiment and were randomly assigned to receive daily either SCB supplementation (10 × 10⁹ cfu/d) or a placebo (CON). Individual feed intake and body weight were monitored on a daily and weekly basis, respectively. Fecal samples were collected at arrival to the veal facility (wk 0) and additional samples were taken on d 14 (wk 2) and d 49 (wk 7). These samples were subjected to 16S rRNA gene amplicon sequencing using Illumina MiSeq (Illumina Inc., San Diego, CA) to examine the bacterial profiles and real-time quantitative PCR to quantify Saccharomyces cerevisiae and specific bacterial groups. The significant increase of S. cerevisiae in the feces of SCB calves at wk 2 and 7 compared with wk 0 (respectively 1.7 × 10⁷, 1.2 × 10⁷, and 2.2 × 10⁵ copy number of S. cerevisiae/g of feces) indicates a good survival of that yeast strain along the gastrointestinal tract. Supplementation of SCB did not improve overall growth performance with regard to average daily gain (ADG), final body weight, and feed intake. Nevertheless, a total of 69.1% of nonsupplemented calves had diarrhea and 28.6% experienced severe diarrhea, whereas 50.0% of the calves supplemented with SCB had diarrhea and 9.5% experienced severe diarrhea. With respect to antibiotic use, 89.7% of the diarrheic calves recorded in the CON group were treated, whereas only 66.7% of the SCB diarrheic calves received an antibiotic. In addition, diarrheic calves supplemented with SCB maintained an ADG similar to nondiarrheic animals, whereas the CON diarrheic calves had a significantly lower ADG in comparison with nondiarrheic CON calves. Fecalibacterium was the most predominant bacterial genus in fecal samples of nondiarrheic and diarrheic calves supplemented with SCB, whereas fecal microbiota was predominated by Collinsella in diarrheic calves from the CON group. Live yeast supplementation in milk replacer led to a decrease of diarrhea in milk-fed veal calves and the fecal microbiota of diarrheic calves maintained a healthy community similar to nondiarrheic animals, with Fecalibacterium being the predominant genus.