Associations among antimicrobial use, calf management practices, and antimicrobial resistance in Escherichia coli from a pooled fecal sample in calves on Canadian dairy farms: A cross-sectional study.

The objective of this cross-sectional study was to determine associations between calf management practices, the number of antimicrobial treatments, and antimicrobial resistance in preweaning heifers on Canadian dairy farms. A composite of 5 fecal samples from preweaning calves was collected from 142 dairy farms in 5 provinces and analyzed for phenotypic antimicrobial susceptibility with the microbroth dilution method. Questionnaires were used to capture herd characteristics and calf management practices used on the farm. Calf treatment records were collected during the farm visits. Escherichia coli was isolated from all 142 fecal samples with the highest resistance to tetracycline (41%), followed by sulfisoxazole (36%), streptomycin (32%), chloramphenicol (28%), ampicillin (16%), trimethoprim-sulfamethoxazole (15%), ceftriaxone (4.2%), cefoxitin (2.8%), amoxicillin-clavulanic acid (2.1%), ciprofloxacin (2.1%), nalidixic acid (2.1%), azithromycin (1.4%), and gentamicin (1.4%). Multidrug resistance was observed in 37% of E. coli isolates. Three-quarters of farms used fresh colostrum as the most common type of colostrum fed to calves. Colostrum quality was checked on 49% of farms, but the transfer of passive immunity was only checked on 32% of farms in the last 12 mo. Almost 70% of farms used straw or hay or a combination as the bedding material for calves. Among the 142 farms, a complete set of calf records were collected from 71 farms. In a multivariable logistic regression model, farms with ≥1.99 to 32.57 antimicrobial treatments/calf-year were 3.2 times more likely to have multidrug resistant E. coli in calf feces compared farms with <1.99 antimicrobial treatments/calf-year. Farms using hay or straw beddings were 5.1 times less likely to have multidrug resistant E. coli compared with those with other bedding materials including shavings or sawdust. Bedding management practices on farms may need to be investigated to reduce the potential effect on disseminating multidrug resistant bacteria.

Randomized control trial to investigate compliance with, and impacts of, cow comfort recommendations on smallholder dairy farms in Kenya.

Smallholder dairy farmers (SDF) in developing countries often have limited understanding on the importance of cow comfort. We conducted a randomized controlled trial with 124 cows on 114 Kenyan SDF to determine the status of cow comfort, to assess compliance to farm-specific cow comfort recommendations, and to evaluate the impacts of the farm-specific interventions on cow comfort. On the first farm visit, stall dimensions and characteristics (e.g. stall base hardness and hygiene) were measured and categorized as adequate, marginal or inadequate/absent based on cow size. Where measurements were not adequate, farm-specific cow comfort recommendations were provided in written and oral form to the randomly allocated intervention group of farms (n = 74). On the second farm visit two months later, the same measurements were taken, and percent compliance to the recommendations was evaluated. A discomfort index was arithmetically calculated based on the stall base hardness (scale was 1-3 for soft to hard) and hygiene (scale was 1-5 for clean to dirty). Multivariable linear regression models were used to determine specific associations with the discomfort index. On the first visit, the mean stall base hardness and stall hygiene scores were 1.7 and 2.3, respectively, for a mean discomfort index of 4.0. Intervention farmers were given 3.9 comfort recommendations, on average, and complied with 2.1 recommendations, significantly improving the discomfort index at visit two to 3.3. The overall compliance to the recommendations was 49.0%. In a final model, the interaction between intervention group and visit number was significantly associated with discomfort index, indicating that after adjusting for baseline discomfort indices, the intervention led to better cow comfort. Specifically, bedding type and neck rail positioning were significantly associated with discomfort index. We concluded that farmers can substantially improve cow comfort on SDF by providing recommendations to them. Farm advisors should include cow comfort recommendations to SDF.

Associations of calf management practices with antimicrobial use in Canadian dairy calves.

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.

Evaluation of environmental and comfort improvements on affective welfare in heifer calves on smallholder dairy farms.

A controlled trial on zero-grazed smallholder dairy farms was conducted to determine the effect of environmental and comfort improvements on sucking and lying behaviours in heifer calves on Kenyan smallholder dairy farms. The study involved 187 heifer calves from 150 farms in two Kenyan counties, 75 farms per county. Farms in one county received animal welfare training and improvements in the calf pen that included: 1) placement of rubber mats on the lying area; 2) fixing gaps/holes in the flooring and roofing; and 3) attaching a rubber nipple on the wall of the calf pen. During the 16-month data collection period, bimonthly farm visits were used to collect data on lying time (using accelerometers) and other animal- and farm-level factors. Multilevel mixed-effects linear regression was used to model daily lying times and frequency of lying bouts, with the animal as a random effect. Over the visits, daily lying times and lying bout durations averaged 12.6-86.7 min/bout, respectively, while the median for the frequency of lying bouts was between 30-46/day. Provision of rubber nipples for non-nutritive sucking lowered proportions of cross-sucking, self-sucking and object-sucking behaviours slightly but not significantly. In a final daily lying time model, superficial lymph node enlargement, body condition score and use of wood shaving/ sawdust/ crop waste as beddings had positive associations. In contrast, group housing and rubber mat use had negative associations with daily lying time. In an interaction term, lying time was significantly higher for calves on clean versus dirty floors if the age was <190 days but this difference diminished significantly in older animals. In a second interaction term, lying time was lower for calves with leaking versus non-leaking roofs, regardless of the pen floor level, but lying time was higher on elevated than non-elevated floors if the roof was intact. In the final model of the frequency of lying bouts, the use of a rubber mat, the years of experience in dairy farming, and calf body weight had negative associations. In contrast, body condition score had a positive association. In an interaction, the frequency of daily lying bouts was lower on clean floors than dirty floors, irrespective of tethering status, but when the floor was dirty, the lying bouts were higher for animals not tethered than the ones sometimes tethered. We conclude that the comfort improvements enhanced the welfare and lying experience of heifer calves on smallholder dairy farms.

Management factors associated with time-to-onset and fecal egg/oocyst counts of gastrointestinal parasites in heifer calves on Kenyan smallholder farms.

A prospective cohort study on zero-grazed smallholder dairy farms was conducted to determine factors associated with onset and counts of gastrointestinal parasitism in heifer calves. The researchers recruited 187 newborn heifer calves from 150 farms in Kenya. Over 16 months, farm visits every two months were used to collect rectal fecal samples and animal- and farm-level measures. Fecal samples underwent centrifugal fecal flotation with Sheather's sugar to determine counts of strongyle-type eggs and coccidia oocysts. Cox proportional hazard (Cox PH) analysis and mixed-effects negative binomial (MeNB) regression determined factors associated with time-to-onset and counts of strongyle-type eggs and coccidia oocysts, respectively (P < 0.05). The incidence rate of strongyles was 0.0011 cases/animal-day while coccidia was 0.0073 cases /animal-day. Incidence risks of strongyles and coccidia over the study period were 28.3 % (53/187) and 87.7 % (164/187), respectively. For infected calves, median time-to-onset for strongyles and coccidia was 78 (interquartile-range: IQR 38-117) and 43 (IQR 29-92) days, respectively. In the final Cox PH model for strongyles, breed (Ayrshires and Jerseys) and weaned calves had a greater hazard of infection than Friesians and preweaned calves, respectively. Calf tethering outside the pen was associated with a higher hazard of strongyle infection. In the final Cox PH model for coccidia, calves with watery and/or hemorrhagic diarrhea had a higher hazard compared with those with hard or soft feces. Weaning status and birth weight (kg) were time-varying covariates, leading to increased hazard over time. In the final MeNB model for strongyles, weaned animals had higher counts than those still on milk. In an interaction variable, the predicted strongyle-type egg counts increased with longer duration of farm operation when herd size was less than five cattle, but decreased when herd size was more than five. In the final MeNB model for coccidia, calves sometimes tethered outside their pens had higher counts than those continuously enclosed in the pen. Calf pen floors with either scant manure or moderate slurry had higher predicted counts than those on a clean pen floor. Calves with watery or hemorrhagic diarrhea and fed fresh Napier grass (Pennisetum purpureum) had higher counts compared with soft or hard feces and those not given fresh Napier, respectively. In an interaction variable, calves experiencing diarrhea and raised on elevated slatted floors had lower oocyst counts compared with those having diarrhea but not on elevated floors. The identified management practices associated with onset and counts of gastrointestinal parasitism should be considered in control efforts.

Using serum and plasma samples to assess failure of transfer of passive immunity in dairy calves.

The objectives of this study were (1) to determine the differences in IgG and total protein (TP) content of serum and plasma samples collected from the same calves; (2) to evaluate the correlation between calf serum and plasma IgG levels, Brix scores, and TP concentrations; (3) to determine whether different cut-off values should be used for plasma and serum to assess failure of transfer of passive immunity (FTPI) in dairy calves; and (4) to evaluate the level of agreement between results obtained from using serum and plasma samples of the same calves to assess FTPI using optimal cut-off values. Blood samples (n = 217) were collected from Holstein calves at 3 to 10 d of age on 30 commercial dairy farms in Nova Scotia and Newfoundland, Canada. Paired serum and plasma samples were analyzed for IgG concentration by the reference radial immunodiffusion assay, transmission infrared (TIR) spectroscopy, digital and optical Brix refractometers, and optical TP refractometer. The IgG concentrations measured by RID and TIR spectroscopy in serum were similar to those in plasma. However, the Brix and TP refractometer readings were significantly higher in plasma than in serum. The prevalence of FTPI in serum and plasma samples based on a RID-IgG concentration <10 g/L was 43.3 and 46.5%, respectively. The RID-IgG concentration was correlated with TIR-IgG (r = 0.92 and 0.89), digital Brix (r = 0.80 and 0.80), optical Brix (r = 0.77 and 0.77), and optical TP (r = 0.75 and 0.77) refractometers in serum and plasma, respectively. The correlations between paired serum and plasma IgG content were 0.85 by TIR spectroscopy, 0.80 by digital Brix, 0.77 by optical Brix, and 0.79 by optical TP refractometer. The optimal cut-off values for TIR spectroscopy, digital Brix, optical Brix, and TP refractometers to assess FTPI using serum were 13.1 g/L, 8.7% Brix, 8.4% Brix and 5.1 g/dL, respectively; and the optimal cut-off values with plasma were 13.4 g/L, 9.4% Brix, 9.3% Brix and 5.8 g/dL, respectively. When using these optimal cut-off values, the level of agreement (88.1%) between results derived from testing serum and plasma by TIR spectroscopy was substantial, with a kappa (κ) value of 0.76. The results derived from testing serum and plasma by digital Brix refractometer showed substantial agreement (83.4%), with a κ value of 0.65, which is higher than the agreement and κ value (74.7% and 0.51) reported for the optical Brix refractometer. Substantial agreement (81.6%) between serum and plasma TP was also obtained when using the optical TP refractometer, with a κ value of 0.63. In conclusion, serum or plasma samples can be used interchangeably for measuring IgG concentrations and assessing FTPI in dairy calves. However, different cut-offs must be used to assess FTPI depending on the sample matrix. Furthermore, results obtained from serum samples showed higher agreement with the reference RID assay than those obtained from plasma samples.

Short communication: Extended-spectrum cephalosporin-resistant Escherichia coli in colostrum from New Brunswick, Canada, dairy cows harbor blaCMY-2 and blaTEM resistance genes.

Dairy calves are colonized shortly after birth by multidrug resistant (MDR) bacteria, including Escherichia coli. The role of dairy colostrum fed to calves as a potential source of MDR bacteria resistance genes has not been investigated. This study determined the recovery rate of extended-spectrum cephalosporin-resistant (ESC-R) E. coli in colostrum from cows. The ESC-R E. coli isolates were further investigated to determine their phenotypic antimicrobial resistance pattern and the genes conferring ESC-R. Fresh colostrum was collected from 452 cows from 8 dairy herds in New Brunswick, Canada. The ESC-R E. coli was isolated from the colostrum by using the VACC agar, a selective media for extended-spectrum ß-lactamase producing Enterobacteriaceae. Minimum inhibitory concentration was determined for all the suspected ESC-R E. coli isolates using a commercial gram-negative broth microdilution method. Two multiplex PCR were conducted on all the suspected ESC-R E. coli isolates to determine the presence of the blaCTX-M (groups 1, 2, 9, and 8/25) blaCMY-2, blaSHV, and blaTEM resistance genes. The ESC-R E. coli were detected in 20 (4.43%) of the colostrum samples. At least 1 ESC-R E. coli isolate was detected in 6 (75%) of the dairy herds. All ESC-R E. coli had MDR profiles based on minimum inhibitory concentration testing. No blaCTX-M groups genes were detected; however, the blaCMY-2 gene was detected in 9 or 20 (45%) and blaTEM was detected in 7 of 20 (35%) of the ESC-R E. coli. No ESC-R E. coli had both blaCMY-2 and blaTEM resistance genes. This is the first report of blaCMY-2 and blaTEM genes found in E. coli isolates cultured from dairy colostrum to our knowledge.

Rapid assessment of bovine colostrum quality: How reliable are transmission infrared spectroscopy and digital and optical refractometers?

The objectives of this study were to evaluate the performance of the transmission infrared (IR) spectroscopic method and digital and optical Brix refractometers for measurement of colostral IgG concentration and assessment of colostrum quality of dairy cows. Colostrum samples (n = 258) were collected from Holstein cows on 30 commercial dairy farms in Nova Scotia and Newfoundland, Canada. Colostral IgG concentrations of 255 samples were measured by the reference radial immunodiffusion (RID) assay and IR spectroscopy. The Brix scores were determined on 240 of these samples using both the digital and optical Brix refractometers. Approximately half (48%) of the colostrum samples had RID IgG concentrations <50 g/L, which was the cut-point for poor quality. The correlation between RID and IR IgG concentrations was 0.88. The correlations between RID IgG concentration and Brix scores, as determined by the digital and optical refractometers, were 0.72 and 0.71, respectively. The optimal cutoff levels for distinguishing good- and poor-quality colostrum using IR spectroscopy, and digital and optical Brix refractometers were at 35 g/L and 23% Brix, respectively. The IR spectroscopy showed higher sensitivity (90%) and specificity (86%) than the digital (74 and 80%, respectively) and optical (73 and 80%, respectively) Brix refractometers for assessment of colostrum quality, as compared with RID. In conclusion, the transmission-IR spectroscopy is a rapid and accurate method for assessing colostrum quality, but is a laboratory-based method, whereas Brix refractometers were less accurate but could be used on-farm.

Presumptive diagnosis of Clostridium botulinum type D intoxication in a herd of feedlot cattle.

Fifty-two feedlot cattle exhibited clinical signs suggestive of botulism. Clostridium botulinum type D organisms were recovered from ruminal fluid of 4 of the 5 affected animals tested and were isolated from bakery waste fed to the cattle. Clostridium botulinum type D has not been reported previously in Canadian cattle.

Costs of clinical mastitis and mastitis prevention in dairy herds.

A stratified random sample of 50 Ohio dairy herds, monitored for 1 year between March 1988 and May 1989, was used to estimate the component costs of clinical mastitis per cow-year overall and by organism, the component costs of an episode of clinical mastitis overall and by organism, and the incidence of clinical mastitis by organism. Each herd was visited monthly by a veterinarian who conducted on-farm interviews and completed standardized data-collection forms designed to elicit economic information about the on-farm costs of clinical mastitis and mastitis prevention. Producers collected milk samples prior to treatment of clinical mastitis cases. Culturing methods allowed identification of 18 specific mastitis pathogen classifications. Annual costs estimated were on a per cow-year and clinical episode basis. The monthly mean population of cows monitored was 4,068. Mastitis prevention cost $14.50/cow-year, whereas the cost incurred by producers because of clinical cases of mastitis was $37.91. Organisms prevalent in the cows' environment caused the most costly types of mastitis. Disregarding contaminated samples and episodes for which no milk samples were taken, mastitis for which 2 organisms were isolated accounted for 35.5% of costs of clinical mastitis, followed by cases for which Escherichia coli (21.3%) was isolated, cases for which culturing yielded no growth (8.6%), and cases for which esculin-positive Streptococcus spp (6.4%), Klebsiella spp (5.7%), esculin-negative CAMP-negative Streptococcus spp (5.1%), Enterobacter spp (4.8%), coagulase-negative Staphylococcus spp (4.1%), coagulase-positive Staphylococcus spp (3.0%), S agalactiae (2.5%), and Bacillus spp (1.2%) were isolated.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevalence of contagious pathogens of bovine mastitis and use of mastitis control practices.

A cross-sectional study of 1,032 dairy herds in Ohio was conducted to determine the prevalence of the major contagious pathogens of mastitis (Streptococcus agalactiae and Staphylococcus aureus) and the use of common mastitis control measures. Herd owners were surveyed by mail concerning their use of mastitis control measures. The survey focused on treatment of nonlactating cows, postmilking teat dipping, culling practices, milking machine maintenance, treatment for clinical mastitis, and premilking hygiene practices. Nearly 90% of questionnaires were returned. The prevalence of Streptococcus agalactiae and Staphylococcus aureus was determined by use of bulk-tank milk samples. Most herds (n = 802) met the criteria for classification into 1 of 4 groups: (1) Free of contagious pathogens, as determined by inability to isolate coagulase positive staphylococci (CPS) and esculin-negative CAMP positive streptococci (ENCPS) from 3 bulk-tank milk samples, (2) CPS, but not ENCPS, isolated from at least 1 sample, (3) ENCPS, but not CPS, isolated from at least 1 sample, (4) both ENCPS and CPS isolated from at least 1 sample. The number of herds in which both ENCPS and CPS were isolated was low; therefore, these herds were grouped with herds in which ENCPS alone was isolated for the evaluation of mastitis control practices related to herd pathogen status. Herd somatic cell count (SCC) was determined using Dairy Herd Improvement Association data by calculating the geometric mean SCC from individual cow test day SCC. Twelve months of SCC data from 741 herds were included in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of environment and management on mortality in preweaned dairy calves.

Forty-eight herds participating in the 1988/1989 Ohio National Animal Health Monitoring System dairy project were monitored for 1 year to determine the effects of environment and management on mortality in preweaned calves. Environmental factors were evaluated by veterinarians during monthly visits to the herds. Management procedures were measured through the use of a questionnaire administered near the end of the project. Mortality in preweaned calves was calculated for each herd by using data from project records on calf mortality and animal inventory, which were collected monthly by veterinarians. Relationships between the management/environment variables and calf mortality were examined by use of analysis of covariance. Herd size, days on a nipple feeder, navel disinfection, type of housing, and whether each calf observed with diarrhea was treated with antibiotics were the variables that had an impact on herd mortality. These variables explained approximately 39% of the variation in mortality among herds.

Managerial risk factors of intramammary infection with Streptococcus agalactiae in dairy herds in Ohio.

Dairy herds in Ohio were selected by stratified random sampling for participation in a disease-monitoring study to relate Streptococcus agalactiae intramammary prevalence to herd management and environmental conditions. Of 48 herds studied, 27 herds had at least 1 cow infected with this pathogen. Management and environmental conditions were assessed by direct observation as well as by an interview with the dairy producers. One-way ANOVA or chi 2 analysis, with presence or absence of Streptococcus agalactiae as the dependent variable, was used to test each of 70 independent variables. Variables found significant at P less than 0.20 were further evaluated by use of logistic regression. Our sample size permitted only 4 independent variables to be simultaneously evaluated by logistic regression. The most predictive risk factors were identified as poor teat and udder hygiene, poor environmental sanitation, large herd population, and use of a shared washcloth for premilking cleaning of teats and udders.

Salmonella infections in neonatal dairy calves.

To estimate herd prevalence of Salmonella spp, fecal specimens were obtained for culture from neonatal calves of 47 Ohio dairy herds. Of the 452 calves tested, 10 calves from 7 farms were culture-positive. Salmonella serotypes isolated were S dublin, S typhimurium, S enteritidis, S agona, S mbandaka, and S montevideo. Bulk tank milk filters from these dairies were also submitted for culture. Salmonella sp was isolated from 1 of the 50 filters, and 2 calves from this herd were found to be shedding Salmonella sp of the same serotype.

Managerial determinants of intramammary coliform and environmental streptococci infections in Ohio dairy herds.

Forty-eight dairy herds in Ohio were selected as a stratified random sample for participation in a disease monitoring study to relate the prevalence of IMI with coliform and environmental streptococci to herd management and environmental conditions. Management and environmental conditions were assessed by farm inspection and by an interview with the dairy producers. A separate analysis for each independent variable identified many potential disease determinants. A multivariable analysis of a covariance model to predict the prevalence of coliforms had 6 model df (R2 = .47). Increased prevalence of coliform infection was associated with an increased amount of milk remaining in the udder after milking, use of free stalls, regular use of a running water wash, increased person hours per cow spent milking, and poor sanitation. The multivariable model for environmental streptococci used 5 model df (R2 = .51). Increased prevalence of environmental streptococci was associated with poor sanitation, increased number of days dry, use of tie stalls, no use of a shared wash cloth, and no use of an individual dry cloth.

Serologic enzyme-linked immunosorbent assay responses of calves vaccinated with a killed Mycobacterium paratuberculosis vaccine.

The purpose of this study was to document the effect of calfhood vaccination for Mycobacterium paratuberculosis on a serologic ELISA. Fifteen calves vaccinated with a killed paratuberculosis vaccine and 5 unvaccinated control calves were tested from the first through the fifteenth month of life. Age of vaccination ranged from 5 to 40 days. Blood samples were collected prior to vaccination and periodically thereafter. Serum antibody was analyzed by use of the ELISA. All calves were ELISA-negative prior to vaccination. Thirteen of 15 vaccinated calves became ELISA-positive between 2 and 6 months after vaccination. The unvaccinated cohort remained ELISA-negative. Wide-spread use of vaccine may interfere with diagnosis of paratuberculosis and with control programs that are based on serologic tests that measure humoral antibody.