Updated targets for measuring transfer of passive immunity (TPI) at the herd level have been suggested, but the current performance of dairy herds in Great Britain is unknown. A cross-sectional study was performed. Serum total protein (STP) data collected between October 2022 and October 2023 by 21 veterinary practices were benchmarked. Questionnaires were also distributed to collect information about colostrum feeding, calf husbandry and veterinary engagement, and associations between these factors and herd TPI were analysed using ordinal logistic regression. A total of 4455 STP results from 91 herds were collected. Overall, 26% of calves had an STP concentration of less than 52g/L (n = 1144). The number of herds with less than 10% of measured calves having an STP concentration of less than 51g/L was 26% (n = 24). In contrast, 44% of herds (n = 40) recorded more than 40% calves having an STP concentration of 62g/L or more. Herd TPI score was negatively associated with colostrum replacer feeding (odds ratio 0.09, 95% confidence interval: 0.01-0.54, p = 0.01). A limited number of veterinarians and farmers completed the accompanying questionnaire, increasing the likelihood of Type I statistical error. Survey responses may be influenced by response bias. The overall herd TPI measured in the study was inadequate, suggesting that renewed emphasis on the optimisation of TPI within British dairy herds is necessary.

ABSTRACTBackgroundLung auscultation is a common method for the routine diagnosis of calf bronchopneumonia. However, its repeatability among operators has been criticized.ObjectiveDetermine agreement among veterinarians for specific lung sounds after a short tutorial to standardize the definition of lung sounds.AnimalsForty lung sounds from a larger dataset collected at 4 veal calf farms that housed 495–815 animals were submitted online to 10 different veterinarians.MethodsAfter a short tutorial on lung sound auscultation, the raters were asked to detect the presence of any abnormal sounds and to differentiate among wheezes, crackles, and bronchial sounds. Raw percentage of agreement (PA), Gwet's agreement coefficient type 1 (AC1), Krippendorff's alpha (Ka), and Fleiss kappa (KFleiss) were chosen as agreement indicators in the absence of a gold standard indicator to assess agreement. The different indicators were interpreted based on a priori reported benchmarks.ResultsThe agreements were fair to good for almost all lung sound indicators. For the presence of any abnormal lung sound, the reported agreements (95% confidence intervals [CI]) were 0.781 (0.716–0.845), 0.646 (0.514–0.777), 0.403 (0.351–0.455), and 0.293 (0.137–0.493) for PA, AC1, Ka, and KFleiss, respectively. The same indicators were 0.769 (0.694–0.845), 0.615 (0.446–0.784), 0.426 (0.378–0.475), and 0.425 (0.293–0.563) for wheezes, 0.754 (0.685–0.823), 0.643 (0.503–0.782), 0.21 (0.146–0.275), and 0.208 (0.097–0.327) for crackles, and 0.636 (0.571–0.701), 0.345 (0.179–0.512), 0.182 (0.131–0.232), and 0.18 (0.081–0.279) for bronchial sound detections, respectively.Conclusion and Clinical ImportanceAgreement among raters auscultating calf respiratory sounds was higher than previously reported. However, improvement is still possible to increase auscultation agreement.

Objective: This study assesses calf-rearing practices and their effects on calf mortality in the TRC1 region of Southeastern Anatolia, Türkiye. By classifying farms into low, medium, and high mortality groups, it identifies key factors impacting calf survival and offers insights to enhance calf health, reduce mortality, and improve dairy farm sustainability. Material and Methods: The study was conducted in Türkiye's TRC1 region, home to around 388,000 dairy cattle. Data were gathered from 145 dairy farms during the 2019-2020 cycles via stratified random sampling. Farms were grouped by mortality rate using K-means clustering. Statistical tests (ANOVA, Kruskal-Wallis, t-test, Mann-Whitney U test) and multiple regression analysis assessed factors such as colostrum intake, milk feeding frequency, and weaning age on calf mortality. Results: Significant variability in calf-rearing practices was observed. Average colostrum intake was 2.64 liters initially and 3.15 liters for the second feeding, with wide ranges. Milk was fed 2.08 times per day, and weaning ages spanned 30-180 days. Low-mortality farms had higher colostrum intake and consistent feeding schedules. Regression analysis identified colostrum intake, milk feeding frequency, and weaning age as significant calf mortality predictors. Conclusion: The study underscores the importance of early calf management on mortality rates. Improved colostrum intake, feeding frequency, and appropriate weaning age can enhance calf survival and farm profitability, offering valuable guidance for dairy farmers. Keywords: Calf feeding practices, Calf health, Calf mortality, Colostrum intake, Dairy farm management, Farm sustainability.

Introduction: In this Cattle Review, we look at a paper considering the application of bovine appeasing pheromone in calf husbandry, a recent international review of Johne's disease control through advancements in diagnostics, testing and youngstock management and a paper reporting the recent Bluetongue outbreaks in the Netherlands. All three papers are open access and available online.

The article talks about the conducted research on the infection of calves with eimeriosis depending on the age and seasons of the year in livestock farms located in Khachmaz and Shabran regions of Guba-Khachmaz economic region, also Bilasuvar and Hajigabul regions of Shirvan-Salyan economic regions. During the researches were studied spread of eimeria parasitizing on calves in farms depending on the seasons and the age of the animals. Depending on the age eymeriosis infection were determined 33.3% in Khachmaz region, 25.0% in Shabran region, 15.2% in Bilasuvar region, and 21.2% in Hajigabul region. As a result of examinations carried out in calves according to the seasons of the year was found infection eimeria: 38.1% in spring, 9.5% in summer, 28.6% in autumn, 14.3% in winter in Khachmaz region; 27.8% in spring, 5.6% in summer, 16.7% in autumn, 11.1% in winter in Shabran region; 30.4% in spring, 4.3% in summer, 17.4% in autumn, 8.7% in winter in Bilasuvar region; 21.1% in spring, no infection in summer, 15.8% in autumn, 5.3% in winter in Hajigabul region. The presence of factors (temperature, moisture, oxygen) necessary to the development of Eimeria oocysts in spring and autumn has a positive, and the decrease in air temperaturse in winter has a negative effect on the development of Eimeria oocysts.

Risk factors for antimicrobial usage and diseases in Dutch veal calf farms: A cross-sectional study

Molecular characterisation of Mycoplasma bovis isolates from consecutive episodes of respiratory disease on Dutch veal farms

Babesiosis and anaplasmosis are major constraints to livestock production in many developing countries including Kenya. Therefore, their epidemiological data needs to be constantly updated. The current study was aimed at estimating the seroprevalence of Babesia bigemina and Anaplasma marginale and determine their associated risk factors among calves aged 3–12 months in Narok County, Kenya. A cross-sectional study was undertaken in Narok County, Kenya, between February and May 2023. A total of 402 calves from 76 farms were randomly selected from 8 villages in Sub-Counties of Naroosura Majimoto and Ololulunga. Data on individual calf and individual farm factors was collected via closed-ended questionnaires administered to someone who was involved the calves’ management. Blood was collected from the calves and processed for microscopy (smears) and serology (indirect ELISA using monoclonal antibodies), respectively. Descriptive analysis was performed for both categorical and continuous variables. Mixed effect logistic regression analysis was used to determine the association between seropositivity of the various risk factors with the random effect being the farm. The overall estimation seropositivity of B. bigemina, A. marginale and mixed infections of B. bigemina and A. marginale was 60%, 60% and 38.1% respectively. The overall prevalence on microscopy for B. bigemina, A. marginale and mixed infections of B. bigemina and A. marginale was 22.9%, 32.6% and 11.4%, respectively. Factors significantly associated with the seropositivity of the infections were increase in age (OR=2.736 for A. marginale, 3.030 for B. bigemina and 2.073 for A. marginale/B. bigemina), calves that receive acaricide treatment (OR=0.445 for A. marginale and 0.536 for A. marginale/B. bigemina) and infection history on the farm (OR=3.803 for A. marginale/B. bigemina). In conclusion, the seroprevalence of B. bigemina and A. marginale was relatively high. Control and prevention efforts should be enforced to reduce the risk of clinical diseases from the hemoparasites.

This study on veal calf respiratory disease assessed the association between an on-farm clinical scoring system and lung ultrasonography with the postmortem inspection of the lungs. The comparisons allowed the calculation of predictive values of the diagnostic methods. In total, 600 calves on an Austrian veal calf farm were examined at the beginning and the end of the fattening period. Overall, the area under the curve (AUC) for ultrasonographic scores was 0.90 (rsp = 0.78) with a sensitivity (Se) of 0.86. The specificity (Sp) was 0.78, and the positive predictive value (PPV) was 0.74. The AUC for the physical examination was 0.76 (rsp = 0.55) with a Se of 0.64, an Sp of 0.81, and a PPV of 0.69. For the combination of ultrasonography and physical examination, an AUC curve of 0.85 (rsp = 0.69) was calculated. A Se of 0.65 and a Sp of 0.88 with a PPV of 0.73 was calculated. This study concluded that both physical and ultrasonographic examination scoring are reliable examination methods for the detection of lung diseases in veal calves.

Bedding materials are important for suckling buffalo calves. Treated dung has been used as a bedding material for dairy cows but the lack of an appropriate safety assessment limits its application. In this study, we evaluated the feasibility of treated dung (TD) as a bedding material for suckling calves by comparing TD with rice husk (RH) and rice straw (RS) bedding materials. The TD was prepared through high-temperature composting by Bacillus subtilis. Thirty-three newborn suckling buffalo calves (Bubalus bubalis, 40.06 ± 5.79 kg) were randomly divided into 3 bedding material groups (TD, RH, and RS) and bedded with 1 of the 3 bedding materials for 60 d. We compared cost, moisture content, bacterial counts, and microbial composition of the 3 bedding materials, and investigated growth performance, health status, behavior, rumen fermentation, and blood parameters of bedded calves. The results showed that TD contained the fewest gram-negative bacteria and coliforms on d 1 and 30 and the lowest relative abundance of Staphylococcus throughout the experiment. The RH and TD bedding materials had the lowest cost. Calves in the TD and RS groups showed a higher dry matter intake, and final body weight and average daily gain in the TD and RS groups tended to be higher than in the RH group. Calves in the TD and RS groups had a lower disease incidence (diarrhea and fever), fewer antibiotic treatments, and lower fecal score than calves in the RH group. Higher contents of IgG, IgA, and IgM were observed in calves of the TD and RS groups than in calves of the RH group on d 10, indicating higher immune ability in TD and RS groups. Furthermore, TD bedding increased the butyric acid content in the calf's rumen, whereas RS bedding increased the acetate content, which might be attributed to the longer time and higher frequency of eating bedding material in the RS group. Considering all of the above indicators, we concluded that TD is the optimal bedding material for calves based on economics, bacterial count, microbial diversity, growth performance, and health status. Our findings provide a valuable reference for bedding material choice and calf farming.

Simple SummaryThe dairy industry in Australia and New Zealand is pasture-based, therefore, monitoring failed transfer of passive immunity (FTPI) is challenging. This study involved a systematic literature search and meta-analysis of papers reporting FTPI data from dairy calves within eight days of birth in Australia and New Zealand, until the end of 2022. An overall prevalence of 33% of FTPI in dairy calves in Australasia and a prevalence of 38% at the farm level were calculated from the meta-analysis, comparable to rates observed elsewhere. Factors, such as the frequency of calf removal from the calving area, time of the first colostrum feed after birth, colostrum volume and quality, and other management practices, were found to play a significant role in FTPI in Australasia.Monitoring and minimizing the prevalence of failed transfer of passive immunity (FTPI) in dairy replacement calves within the first week of life is crucial for calf health and farm profitability. In this study, a systematic literature search and meta-analysis were conducted on papers reporting the prevalence of FTPI in calves from pasture-based dairy farms in Australia and New Zealand. Two search methods, a “traditional method” and a “search engine method”, were conducted to identify published studies on FTPI in Australia and New Zealand. Data from a total of 13,430 calves from eight studies in Australasia were included in the analysis for FTPI within 8 days of birth. The meta-analysis revealed that the average prevalence of FTPI was 33% across the two countries, with the lowest FTPI (9%) in Western Australia and the highest FTPI (59%) in New Zealand. Using farm data from three studies, the average prevalence of FTPI at the farm level in Australasia was 38%, with the lowest prevalence found in a farm in South Australia (6%). In conclusion, the meta-analysis confirmed the need for good management of cows and newborn calves after birth in pasture-based systems to reduce FTPI in calves. Collecting newborn calves from pasture at least twice per day after birth and providing colostrum of sufficient quantity and quality as soon as possible were the best practices for preventing FTPI in Australasian dairy systems.

IntroductionThe association between antibiotic use and the occurrence of resistant bacteria is a global health problem and is subject to enormous efforts at national and international levels. Within the scope of the study “KAbMon”, the resistance situation as well as the use of antibiotics in calf rearing farms in Germany was investigated. We hypothesized that the levels of resistance are associated with certain calf keeping farm types, such as pre-weaned calf farms, animal groups, and therapy frequency.MethodsIn total, 95 calf keeping farms were visited between October 2019 and April 2021. At each farm, up to three pooled fecal samples (10 freshly released feces each) were collected. One sample was taken in the youngest calf group, another in the oldest calf group, and one in the hospital box, if available. Escherichia coli was isolated from non-selective MacConkey agar. The therapy frequency reflects the average number of treatment days per calf in a half-year, while the resistance score is the sum of the relative minimum inhibitory concentration per substance over all 10 tested substances.ResultsThe 1781 isolates from 178 samples showed high resistance rates against sulfamethoxazole (82%), tetracycline (49%), and ampicillin (40%). High resistance scores were mainly found in pre-weaned calf farms (purchasing calves from 2 weeks of life) and in the youngest animals. The therapy frequency showed an almost linear relationship with the resistance scores, and the age at purchase was negatively related to the resistance score.DiscussionThe high use of antimicrobials of young calves might be associated with a high risk for infectious diseases and might indicate that the current system of crowding 14-day-old calves from different farms in one group is not optimal. Further efforts are necessary to educate and motivate the calf keepers to ensure highest levels of hygiene and management as well as animal welfare conditions and to increase animal health.

Successfully rearing beef calves to weaning and beyond determines the economic performance of a beef farm. As such, it is important to understand the factors influencing performance outcomes. This study recorded the health events, mortality and growth rates of 674 calves born on 50 commercial beef farms in Great Britain using a postsampling questionnaire. All calves had a known postcolostral serum IgG status. Preweaning mortality in the study population was 1.5% (10/674 calves), while the treatment rate was 6.4% (43/674 calves). Serum IgG, calf sex and dystocia were significant predictors of whether a calf died and/or required treatment. Average daily liveweight gain was calculated for calves where weaning weights were provided (n = 513). Serum IgG and calf sex were consistent predictors of calf growth rates, while birthweight and whether the calf was born to a cow or heifer were predictive in a model where average daily liveweight gain was converted to a binary response variable using the mean average daily liveweight gain on the calf's farm of origin. Morbidity and mortality were lower than comparable studies, potentially due to limitations in the study design. Serum IgG and calf sex were significant explanatory variables that affected beef calf average daily liveweight gain. For every 5g/L increase in serum IgG, the odds ratio of dying and/or requiring treatment decreased by 0.86.

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

Although calf mortality is a multifactorial problem, little is known about the attitudes and personalities of calf care workers (CCWs) and their association with calf mortality. This study aimed to describe the attitudes, satisfaction, and personality of CCWs in large Estonian dairy herds and to analyze their associations with herd calf mortality. A questionnaire registering CCWs' attitudes toward their work and calf mortality, personality characteristics, satisfaction and importance of different job-related factors was developed. In total, completed questionnaire data of 161 CCWs from 108 large (>100 cows) Estonian dairy farms were analyzed. Herd-level yearly calf mortality risk (MR) was calculated. Cluster analysis and variance partitioning analysis were applied to reveal the explanatory capacity of CCWs' attitudes and personalities on calf mortality. The mean yearly herd-level calf MR was 5.4% during the first 21 days of life and 2.7% during 22–90 days of life. Although good calf health and low calf mortality was important for CCWs, dead calves were often seen as inevitable. CCWs were generally doubtful regarding their capacity and available knowledge to influence calf mortality. In high-mortality herds, CCWs were dissatisfied with the calf health situation and farm working equipment and felt that the situation was out of their control. Despite striving, they had less faith that farmworkers could affect the outcomes, such as calf mortality. CCWs' personality domains explained <5% of the variance in the herd's calf MR, whereas their attitudes and satisfaction explained 20% of the variability in calf MR. The current study revealed the importance of the attitudes and satisfaction of CCWs on calf mortality and highlighted the need to allocate proficient assistance to herds with high calf mortality to mitigate calf health problems and the resulting consequences for CCWs.

Clonal dissemination of MDR Pasteurella multocida ST79 in a small Swiss veal calf farm with high use of antibiotics.

Bovine respiratory disease (BRD) is common in calves in Algeria, but to date, Mycoplasma bovis has never been monitored as a potential etiological agent. Here, to assess the presence (direct detection) and circulation (indirect detection) of M. bovis, broncho-alveolar lavage fluids (BALF) and serum samples were collected from 60 veal calf farms in Algeria. A commercial ELISA kit (ID Screen® ELISA) was used to screen for the presence of specific antibodies against M. bovis in 351 blood sera collected from both diseased and healthy calves, and 69% (241 sera) tested positive. BALFs from the 176 diseased calves were used to screen for M. bovis by real-time-PCR (rt-PCR), and 102 (58%) tested positive. A non-exhaustive set of 53 clones were isolated from 44 calves and further subtyped using polC gene sequencing. No predominant subtype was found, and two clones exhibited a new subtype. Fourteen clones were further characterized by multilocus sequence typing, and results showed a high degree of genetic diversity, with some clones having new alleles and subtypes. The minimum inhibitory concentrations (MICs) of 5 antimicrobials regularly used to treat BRD was determined on 45 clones. Susceptibility profiles showed very broad diversity, confirming the variety of clones actively circulating. We detected clones with high MICs, including increased MICs of enrofloxacin (n = 5). This is the first study to report the presence of M. bovis in Algeria in calves with BRD. This research also finds broad genetic and phenotypic diversity in the actively circulating isolates.

Simple SummaryBovine respiratory disease is one of the most important diseases in group-housed calves worldwide, with impacts on calf welfare and farm economics. Early detection of the disease is important for the well-being of the animals and a targeted treatment. Therefore, tools for an automated monitoring of individual calves would be a breakthrough in health management. In this study, we used an ear-attached accelerometer to evaluate its potential for the early detection of behavioral changes related to respiratory disease in calves. Our result showed that accelerometers are able to detect changes in activity and lying times that can be used to predict respiratory disease before clinical diagnosis.Accelerometers (ACL) can identify behavioral and activity changes in calves. In the present study, we examined the association between bovine respiratory disease (BRD) and behavioral changes detected by an ear-tag based ACL system in weaned dairy calves. Accelerometer data were analyzed from 7 d before to 1 d after clinical diagnosis of BRD. All calves in the study (n = 508) were checked daily by an adapted University of Wisconsin Calf Scoring System. Calves with a score ≥ 4 and fever for at least two consecutive days were categorized as diseased (DIS). The day of clinical diagnosis of BRD was defined as d 0. The data analysis showed a significant difference in high active times between DIS and healthy control calves (CON), with CON showing more high active times on every day, except d −3. Diseased calves showed significantly more inactive times on d −4, −2, and 0, as well as longer lying times on d −5, −2, and +1. These results indicate the potential of the ACL to detect BRD prior to a clinical diagnosis in group-housed calves. Furthermore, in this study, we described the ‘normal’ behavior in 428 clinically healthy weaned dairy calves obtained by the ACL system.

The illicit use of dexamethasone and other glucocorticoids for cattle fattening in livestock production has been widely described; evidence for illegal treatments can be obtained by direct or indirect detection. In our previous study, we applied two-dimensional electrophoresis (2DE) to identify plasma protein markers of dexamethasone administration in veal calves. Comparison of 2DE maps obtained from blood samples before and after treatment showed the disappearance of two protein spots identified as serum paraoxonase/arylesterase 1 precursor (PON1). In the present study, we validated PON1 as a marker by analysing a larger number of samples treated with dexamethasone for illicit use. Analysis of samples from experimental treatment with other glucocorticoids, androgens and oestrogens confirmed that their influence on PON1 could be excluded. The specificity of the PON1 protein marker was verified on expected negative field samples to exclude interfering factors. However, there is poor statistical evidence to support a significant association between the outcome of PON1 and the considered variables. The results on field samples were compared with histological examination of the thymus as a biomarker of corticosteroid treatment monitored in the Italian histological plan for the control of growth promoters in animals. Two suspect cases were identified from two Piedmont farms where other animals had tested positive at histological examination. In conclusion, the absence of PON1 in the plasma of veal calves can indirectly reveal illicit dexamethasone treatment in individual animals and so identify suspect farms for further investigation. It is effective in a period ranging from 3 to about 10 days from illicit treatment, covering a time span that goes beyond the limits of official chemical controls and preceding histological controls on the thymus of slaughtered animals. PON1 detection in plasma can be coupled with other tests to identify illegal dexamethasone use on veal calf farms.

Simple SummaryCalf diarrhea caused by bacteria usually begins to occur 2–3 d after birth. The main pathogenic bacteria are Escherichia coli, Campylobacter, Salmonella, and Clostridium perfringens. Pathogenic E. coli is the main bacterium that causes diarrhea in calves. It invades the body of calves and releases enteric toxins that cause diarrhea. The incidence of calf diarrhea caused by pathogenic E. coli O1 can reach 60–70%, even as high as 90–100% in large-scale calf farms, and the mortality rate can reach over 50%. Therefore, the prevention and treatment of calf diarrhea are extremely important. We established a calf diarrhea model by artificially intervening in the colonization of intestinal microbial flora and studied the influence of pathogenic E. coli on the composition, function, and short-chain fatty acid content of calf feces. Our research shows that pathogenic E. coli O1 can significantly reduce the abundance and diversity of calf intestinal microflora, increase harmful bacteria, reduce the colonization of beneficial bacteria, and reduce the short-chain fatty acid content in feces.Calf diarrhea caused by pathogenic Escherichia coli is a major cause of death in calves, with a mortality rate of over 50%. It is crucial to understand the pathogenesis and development of calf diarrhea for its prevention and treatment. We aimed to study the effect of pathogenic E. coli on the flora composition, function, and short-chain fatty acid (SCFA) content of calf feces using a calf diarrhea model. Sixty-four newborn Holstein calves (40–43 kg) were divided into a normal group (NG; n = 32) and a test group (TG; n = 32). At the beginning of the experiment, the TG were orally administered pathogenic E. coli O1 (2.5 × 1011 CFU/mL, 100 mL) to establish a calf diarrhea model, and the NG were orally administered the same amount of physiological saline solution. The calves of the two groups were subjected to the same feeding and management. Fresh feces samples were collected at different time points and subjected to 16S rRNA high-throughput sequencing and gas chromatography–mass spectrometry to determine the fecal microbial composition and SCFA content. Pathogenic E. coli O1 significantly altered microbiotas composition in the feces of calves, increasing the relative abundance of Proteobacteria and decreasing that of Firmicutes. It also led to a significant increase in the relative abundance of Escherichia-Shigella and a decrease in Lactobacillus, as well as significantly decreased SCFA content. Therefore, we postulate that pathogenic E. coli induces calf diarrhea by causing intestinal florae imbalance and reducing the content of SCFA.