Biosecurity practices of beef cow-calf producers

OBJECTIVE: To evaluate biosecurity practices of cow-calf producers. DESIGN: Cross-sectional survey. SAMPLE POPULATION: 2,713 cow-calf operations were used in phase 1 of the study, and 1,190 cow-calf operations were used in phase 2. PROCEDURE: Producers were contacted for a personal interview between Dec 30, 1996 and Feb 3, 1997 regarding their management practices. Noninstitutional operations with 1 or more beef cows were eligible to participate in the study. Producers who participated in the first phase of the study and who had > or = 5 beef cows were requested to continue in the study and were contacted by a veterinarian or animal health technician who administered further questionnaires. All contacts for the second phase of the study were made between Mar 3, 1997 and Apr 30, 1997. Additional data on use of various vaccines, testing of imported cattle for brucellosis, Mycobacterium paratuberculosis, bovine viral diarrhea, and tuberculosis as well as potential for feed contamination were collected during the second phase of the study. RESULTS: Producers commonly engaged in management practices that increased risk of introducing disease to their cattle such as importing cattle, failing to quarantine imported cattle, and communal grazing. Producers inconsistently adjusted for the increased risk of their management practices by increasing the types of vaccines given, increasing the quarantine time or proportion of imported animals quarantined, or increasing testing for various diseases in imported animals. CONCLUSIONS AND CLINICAL RELEVANCE: Cow-calf herds are at risk for disease exposure from outside sources when cattle are introduced to the herd, and producers do not always adjust management practices such as vaccination schedules and quarantine procedures appropriately to minimize this risk. Veterinary involvement in education of producers regarding biosecurity risks and development of rational and economical biosecurity plans is needed.     

Biosecurity in 116 Danish fattening swineherds: descriptive results and factor analysis

Biosecurity measures are important for the herd's protection against diseases and also to provide nationwide protection against the introduction of exotic diseases. In this paper, we describe the farmers’ choices and routines regarding biosecurity in Danish fattening herds.

Overall, 116 Danish swine fattening herds in three areas of different pig density were interviewed.

Of these herds, 78% purchased weaners from one sow herd only, whereas 10% purchased from >5 sow herds during 1 year. Large herds (>500 finishers) purchased weaners more often than smaller herds (≤500 finishers). Only two swine producers purchased weaners from a market. Almost all herds (95%) received weaners from one sow herd at one time, and only one herd received from >5 sow herds in one batch. Twenty-one percent did not use an effective barrier between the loading area and the stables when delivering pigs for slaughter. Entry rooms (in which clothing and boots are changed) were common at the farm, and the numbers of visitors were generally low (<10 visitors a year).

Factor analysis was performed to find underlying structures of the biosecurity measures in the herd; four factors were chosen (eigenvalue > 3.10). A site scoring high on factor 1 was a large SPF herd, which received weaners from a single source, had biosecurity requirements for the transport vehicles, and had a high level of biosecurity for visitors. A site scoring high on factor 2 was a multi-site farm, which had personnel working on more than one of the sites, only received weaners from one sow herd, had delivering herds placed close to the participating site, and transported animals themselves. A site scoring high on factor 3 was a site which hired commercial transport for slaughter, was situated far from the abattoir and had a high level of biosecurity when loading pigs. A production site scoring high on factor 4 was a large site, which used all-in/all-out management, washed and disinfected between each group, and purchased many weaners.     

Survey of Mycobacterium avium subspecies paratuberculosis serological status in beef herds on community pastures in Saskatchewan

Johne's disease is a well recognized problem in dairy herds. Relatively little information is available on either the prevalence or the control of Johne's disease in commercial cow-calf operations. In the fall of 1999, blood samples were collected during pregnancy testing from cows on community pastures in Saskatchewan. Sera from these cows were analyzed using a commercial ELISA for antibodies to Mycoplasma avium subspecies paratuberculosis. All cows from each herd examined at the community pastures were sampled. Of the 1799 samples tested, 15 had sample to positive (S/P) ratios greater than 0.25 and were considered positive (apparent sample prevalence, 0.8%; 95% CI, 0.4% to 1.5%). If we assume test sensitivity of 25% and specificity of 98% as recommended by the National Johne's Working Group, the true sample prevalence is not significantly different from 0.0%. The ELISA S/P results for the antibody test-positive animals ranged from 0.27 to 2.5. If a herd was classified as positive based on one test-positive animal, the average herd apparent prevalence was 15.2% (95% CI, 7.1% to 28.6%). If the potential for false-positive results was considered with 2 or more positive animals being required for positive herd status, the herd prevalence was 3.0% (95% CI, 0.4% to 13.4%). Because of the very low prevalence in cow-calf herds, future research to identify risk factors and control points should target problem herds and utilize a case-control study design.     

Estimating herd prevalence of bovine brucellosis in 46 USA states using slaughter surveillance

Making valid inferences about herd prevalence from data collected at slaughter is difficult because the observed sample is dependent on the number of animals sampled from each herd, which varies with herd size and culling practices, and the probability of a positive test result, which depends on variable within-herd prevalence levels as well as test sensitivity and specificity. In this study, brucellosis herd prevalence among beef cow-calf operations is estimated from slaughter surveillance data using a method that combines process modeling with Bayesian inference. Inferences are made for two populations; the first population comprises cow-calf beef herds in a typical U.S. state. The second population represents all beef herds in a collection of 46 low-risk states. The Bayesian Monte Carlo method used in this study links process model inputs to observed surveillance results via Bayes Theorem. The surveillance evidence across multiple years is accumulated at a discounted rate based on the probability of introducing new infection into an area. The process model's inputs include herd size, culling rate per herd, within-herd prevalence, serologic test performance, and the probability of successfully investigating positive results. The surveillance results comprise the number of cows and bulls tested at slaughter and the number of affected herds detected each year. The results find at least 95% confidence that brucellosis herd prevalence among beef cow-calf herds is less than 0.014% (3 per 21,500 herds) and 0.00081% (5 per 6,15,770) after 5 years of slaughter surveillance (with no detections of affected herds) in a typical U.S. state and across 46 low-risk U.S. states, respectively. These results were based on conservative modeling assumptions, but sensitivity analysis suggests only slight changes in the results from changing the assumed process model input values. The most influential analytic input was the probability of introducing new infection into a putatively brucellosis-free state or group of states.     

Patterns of stillbirth and dystocia in Ontario cow-calf herds.

The association between a number of individual animal and herd level factors and calving problems in beef cows and heifers were examined. Data were from the 1987 calving season for a subset of 123 herds which maintained individual-animal records, from a sample of 180 randomly selected Ontario cow-calf herds. The median herd dystocia rate was 5.8% and 24.4% of herds had no dystocias. The median herd stillbirth rate was 2.8%, and 33.3% of herds had no stillbirths. Dystocias and stillbirths were much more common in heifers than in cows. Separate statistical models of dystocia and stillbirth for cows and heifers were created. Dystocia in cows was associated with calf sex, previous calving assistance and large breed type and birth weight. Variations in 1987 cow herd dystocia rates were associated with calving season, location and density, and the herd dystocia rate in 1986. Dystocia in heifers was associated with large breed type and calf birth weight. Herd-level management practices associated with increased heifer dystocia rates included breeding heifers to calve earlier than cows and rearing heifers together with the cow herd. Stillbirths for both cows and heifers were associated with calving assistance, particularly hard assistance. Herd-level management and other factors were unassociated with stillbirths.     

Lungworm disease in dairy cattle: symptoms,diagnosis, and pathogenesis on the basis of four case reports

Clinical lungworm disease appears to occur frequently in Dutch dairy herds. Because the clinical diagnosis is difficult to make in adult cattle, the clinical diagnosis, laboratory diagnosis, differential diagnosis, therapy, and prevention are discussed in this article. In addition, four cases of lungworm disease in adult cattle are presented. The main clinical complaints were coughing, decreased milk production, and weight loss. Several lactating cows died in one herd. The disease history of four herds revealed that introduction of susceptible cows or heifers to herds with cows with subclinical patent lungworm infections had resulted in a pasture infection, leading to clinical problems in both the newly introduced and 'resident' cows of the herd. Further history analysis of the fourth herd revealed that re-introduction of lungworm infection by newly purchased cows in a lungworm free herd resulted in clinical lungworm problems in adult and young animals. The fourth case led to the conclusion that lungworm infection must have been re-introduced by cows purchased from another farm.     

Comparison of the Prevalence and Incidence of Infection with Bovine Virus Diarrhoea Virus (BVDV) in Denmark and Michigan and Association with Possible Risk Factors

Based on 2 previous surveys on the occurrence of infection with bovine virus diarrhoea virus (BVDV) in Danish and Michigan dairy herds, the prevalence and incidence of the infection were compared. The presence of certain possible risk factors for the occurrence of infection in the 2 areas were summarized and it was investigated if any of these risk factors had significant effect on the presence of animals persistently infected (PI) with BVDV in the dairy herds. Information on the cattle population density in the 2 areas was obtained from statistical yearbooks. Further information for the individual farms on age distribution, housing of animals, herd size, pasturing and purchasing policy was gathered. The prevalence of PI animals was more than 10 times higher in Denmark as compared to Michigan. In herds without PI animals, the annual incidence of seroconversion as calculated from the age specific prevalence of antibody carriers varied in most age groups between 20–25% in Denmark and between 5–10% in Michigan. All investigated risk factors except for herd size were in favour of a lower prevalence of infection in Michigan. The use of having animals on pasture and at the same time having purchased more than 40 animals within recent 31/2–4 years were significantly associated with presence of PI animals in the dairy herds (p = 0.01) when tested by the Mantel-Haenszel χ². Using mul-tivariable logistic regression, the occurrence of PI animals was found to be significantly related to the study area (Michigan and Denmark) as well as to herd size and purchase intensity.     

Serum copper concentrations in beef cows and heifers

OBJECTIVE: To characterize serum copper status of cows and heifers in beef cow-calf herds throughout the United States and to evaluate use of copper supplements in those herds. DESIGN: Cross-sectional survey. ANIMALS: 2,007 cows and heifers from 256 herds in 18 states. PROCEDURES: Producers participating in a health and management survey conducted as part of the National Animal Health Monitoring System voluntarily allowed serum samples to be obtained from cows and heifers for determination of copper concentration. Results were categorized as deficient, marginally deficient, or adequate. The proportion of cattle and herds (on the basis of mean value of the tested cattle) in each category was determined. Copper concentrations were compared between herds that reportedly used copper supplements and those that did not. RESULTS: Overall, 34 of 2,007 (1.7%) cows and heifers were deficient in copper, and 781 (38.9%) were marginally deficient. In each region, at least a third of the cattle were deficient or marginally deficient. For herds, 92 of 256 (35.9%) were marginally deficient, and 22 (0.8%) were deficient. Approximately half of the producers reported use of copper supplements, but a sizeable proportion of those producers' cattle and herds were classified as marginally deficient or deficient. CONCLUSIONS AND CLINICAL RELEVANCE: Copper deficiency is not restricted to a single geographic region of the United States. Copper deficiency can persist despite reported use of supplements by producers. Veterinarians dealing with beef cow-calf herds that have problems consistent with copper deficiency should not rule out copper deficiency solely on the basis of geographic region or reported use of copper supplements for the herd.     

Prevalence and risk factors associated with bovine viral diarrhea virus infection in dairy herds in Jordan

A cross-sectional study was carried out to determine the seroprevalence and to identify risk factors associated with bovine viral diarrhea virus (BVDV) infection in 62 non-vaccinated dairy herds (671 cows) in Jordan between January and June 2007. Information regarding herd management was recorded through a personal interview with farmers. Antibodies against BVDV were detected using an indirect ELISA test. Chi-square analysis and multivariable logistic regression model were used to identify risk factors for BVDV seropositivity. The true prevalence of antibodies against BVDV in individual cows and cattle herds was 31.6% and 80.7%, respectively. The seroprevalence of BVDV in medium and large size herds was significantly higher than that in smaller herds. There was no significant difference in BVD seroprevalence between different age groups. Random-effects logistic regression model revealed two major factors associated with seropositivity to BVDV; exchange of visits between adjacent farm workers and not isolating newly purchased animals before addition to the herd. The seroprevalence of BVDV in cows located in the northern Jordanian governorates was significantly higher than that in other studied governorates. Results of this study indicated that BVDV is highly prevalent in Jordan and BVDV infection could be controlled by livestock-trade control, and applying strict biosecurity measures in the dairy farms.     

Economic risk analysis model for bovine viral diarrhea virus biosecurity in cow-calf herds

A stochastic model was designed to calculate the cost-effectiveness of biosecurity strategies for bovine viral diarrhea virus (BVDV) in cow-calf herds. Possible sources of BVDV introduction considered were imported animals, including the calves of pregnant imports, and fenceline contact with infected herds, including stocker cattle raised in adjacent pastures. Spread of BVDV through the herd was modeled with a stochastic SIR model. Financial consequences of BVDV, including lost income, treatment costs, and the cost of biosecurity strategies, were calculated for 10 years, based on the risks of a herd with a user-defined import profile. Results indicate that importing pregnant animals and stockers increased the financial risk of BVDV. Strategic testing in combination with vaccination most decreased the risk of high-cost outbreaks in most herds. The choice of a biosecurity strategy was specific to the risks of a particular herd.     

Neospora caninum seroprevalence and associated risk factors in beef cattle in the northwestern United States

A Neospora caninum seroprevalence and risk factor survey of 2585 cows was conducted in 55 beef cow-calf herds located in five northwestern states of the USA. Blood samples were collected by private veterinary practitioners and management practices were surveyed using a mail questionnaire. Producers were randomly selected from those that employed these veterinarians to perform annual herd pregnancy examinations. Questions were asked about animal management, grazing and feeding, immunization and record keeping practices. Blood was collected from a systematically selected sample of cows in each herd, and age, origin, and pregnancy status were recorded. Blood samples were analyzed for antibodies against N. caninum antigen using a monoclonal antibody-based competitive inhibition (CI) ELISA. Overall seroprevalence was 24% and within herd seroprevalence ranged from 3 to 67% with a median of 19%. Within herd seroprevalence and mean inhibition percentage were different between the five states. Herds that managed their cows on range for summer grazing had lower seroprevalence than those that did not, while increased seroprevalence was associated with higher winter stocking density. Cows less than 3 years of age had higher CI ELISA inhibition percent values than cows greater than 6 years of age. No relationship was noted between serologic status and individual cow origin (purchased or raised), or pregnancy status at the time of sampling.     

A survey of the selenium status of beef cows in Alberta.

An epidemiological survey was conducted in Alberta to measure the selenium status in blood of beef cows during the fall and to determine the risk of selenium deficiency among specific geographic regions of Alberta. Three census divisions of Alberta based on the Statistics Canada Census of Agriculture were chosen as the study areas for the project. Soils and plants in area A (Edmonton area) and area B (Calgary area) were known to be deficient in selenium, while soils and plants in area C (southeast corner of Alberta) were known to have adequate levels of selenium. Blood samples were collected from 335 cows on 29 farms from the 3 study areas. These samples were collected from cows that had recently been removed from pasture in October and November 1992. Answers to a short questionnaire pertaining to various herd characteristics and management practices were also obtained for each herd. The average value of selenium for all cows sampled was 2.20 mumol/L. The average value of selenium of cows in areas A and B was 1.93 mumol/L. The average value of selenium of cows in area C was significantly (P < 0.05) higher at 2.70 mumol/L. Nine percent of the cows in the study were considered marginal or deficient in selenium (< 1.27 mumol/L selenium). Herds located in area C, herds that were provided with supplemental feed on pasture, and herds that were pregnancy checked had higher average herd selenium values than did other herds. Cow-calf producers located in areas with selenium-deficient soils should pay particular attention to selenium supplementation for their cows. Some of the negative "geographic" effects on selenium values can be overcome by more progressive management practices.     

Characteristics and management practices associated with milk production in dairy herds in Ohio enrolled in official Dairy Herd Improvement Association programs

OBJECTIVE: To determine herd characteristics and management practices associated with milk production in dairy herds enrolled in official Dairy Herd Improvement Association (DHIA) programs in Ohio. SAMPLE POPULATION: 186 dairy farms in Ohio. PROCEDURE: All herds in official DHIA programs in 9 counties were invited to participate. Information regarding herd characteristics and management practices was obtained, using a standardized questionnaire. Bulk-tank milk samples were obtained for bacteriologic culture. Official DHIA test-day records were obtained, and associations were identified, using multivariable ANOVA procedures. RESULTS: Of 479 eligible producers, 186 (39%) participated, and consecutive bulk-tank milk samples were available for culture from 172 (36%). Streptococcus agalactiae and Mycoplasma spp were not recovered from bulk-tank milk samples, but Staphylococcus aureus was recovered from 64 (37%) herds. Mean (+/- SD) number of lactating cows in participating herds was 97+/-66, with 123 (66%) herds milking < 100 cows. The RHA was significantly associated with number of cows in milk, estimated percentage of herd detected in estrus, reported annual percentage of heifer calves born alive that died before 8 weeks old, percentage days in milk, use of bovine somatotropin during the preceding 2 years, and sex of the person completing the questionnaire. CONCLUSIONS AND CLINICAL RELEVANCE: In this study, the strongest indicator of milk production was number of cows in milk. However, merely adding cows to a herd should not be considered to guarantee increased milk production, because other management traits could be confounded with increased number of cows in a herd.     

A questionnaire on the health, management, and performance of cow-calf herds in Québec.

Questionnaires were mailed to 520 cow-calf producers in Québec in order to compare management practices and herd performance according to herd size (small: < 40 females, or large: > or = 40 females) and in 4 geographic areas for the 1995 calving season. Owners of large herds adopted management practice and preventive measures more often than did owners of small herds. Average calving and weaning rates were 95% and 87% respectively. Average perinatal and preweaning mortality rates were between 4.9% and 5.6%. A greater percentage of owners with large herds than owners of small herds reported diarrhea and pneumonia problems. Among large herds, the number of herds experiencing pneumonia and calf mortality associated with diarrhea tended to be higher in areas of the northwest. Calf mortality due to pneumonia was higher in the northeast. No regional variation was found among small herds. Further research is needed to identify diseases risk factors.     

Risk factors for high herd level calf morbidity risk from birth to weaning in beef herds in the USA

We analyzed data from a national survey of beef cow-calf producers in the USA to quantify the effects of hypothesized risk factors on herd-level calf morbidity risk from birth to weaning. The analysis included 2490 herds from 23 states. Two stepwise logistic regressions were fit to identify factors associated with ≥10% morbidity. The first model included all herds dichotomized into high-morbidity herds with ≥10% morbidity and low-morbidity herds with <10% morbidity. The second model excluded herds with between 5 and 10% morbidity, and compared >/=10% morbidity with 70% of cows and heifers calves in confinement also increased the odds of being a high-morbidity herd (OR=1.8). The population attributable fractions for dystocia and confined calving for the model including all herds dichotomized at 10% morbidity were 0.41 and 0.11, respectively. The summary population attributable fraction for both factors was 0.46.     

Risk factors for interdigital dermatitis and heel erosion in dairy cows kept in cubicle houses in The Netherlands

Risk factors concerning both the pasture and housing seasons for interdigital dermatitis and heel-horn erosion (IDHE) were studied in dairy cows in a cross-sectional study in The Netherlands. The study population included 2,326 cows (41 herds) and 2,751 cows (46 herds) for the pasture and housing seasons, respectively. Of these animals, 545 (23%) showed serious lesions of IDHE (stages 2 and 3) at the end of the pasture season and 1,269 (46%) during housing. Logistic regression of the pasture study indicated that increased parity, solid concrete floor, restricted grazing time, and herd trimming at long intervals were associated with an increased odds of IDHE, while dry cows and lactating cows within 30 days after calving as well as cows on a slatted floor with manure scraper, and grassland with mixed type of soil were associated with lower odds. In the housing study, odds of IDHE increased with parity, administering low- or medium-energy roughage, and introduction of dry cows into the lactating herd at >2 weeks before calving. The presence of long cubicles, knee-bumpers installed in cubicles as well as rearing calves and heifers within the dairy cows' accommodation decreased the odds of IDHE.     

Management practices and their association with reproductive health and performance in Colorado beef herds

An observational study was conducted to quantify the effects of management practices on reproductive performance and disorders of beef cows. The study population consisted of 44 randomly selected Colorado cow-calf herds monitored for disease and reproductive events as part of the National Animal Health Monitoring System. The managers of the herds were surveyed with a standardized questionnaire to determine specific management characteristics of their operations. Data were analyzed using the random-effects multiple logistic regression model. Outcomes of interest were calving rate, herd incidence rates of dystocia and combined reproductive disorders, and calf mortality rate. A higher calving rate was associated (P less than .01) with a decreased percentage of replacement females in the herd, a shorter breeding season, a smaller herd size, and a lower percentage of bulls being used as yearlings. Incidence rates of both dystocia and combined reproductive disorders were found to be lower (P less than .01) in herds that were fed cottonseed cake as a winter supplement, but higher (P less than .01) in herds that were fed grass hay as a winter supplement. Herds located in the mountains of Colorado had lower (P less than .01) incidence rates of dystocia and reproductive disorders than herds located in the eastern plains. Calf mortality rate was found to be higher (P less than .05) with calving seasons that began earlier in the year. Higher calf mortality rates were associated (P less than .05) with an increased incidence of dystocia, the commingling of cattle on summer range, and smaller herd size.     

Management-related risk factors for M. paratuberculosis infection in Michigan, USA, dairy herds

A cross-sectional study was conducted from June through December 1996 to identify management-related risk factors for herd-level M. paratuberculosis infection. Data were collected from 121 participating herds. A two-part questionnaire was administered to gather data on current and previous management practices and herd productivity. A random sample of cows aged ≥24 months was selected from each herd and tested for antibodies to M. paratuberculosis using the IDEXX Antibody ELISA (sensitivity 64%, specificity 96%). A positive herd was one in which ≥2 animals tested positive for antibodies to M. paratuberculosis. A negative herd was one in which no animal tested positive. Herds in which only one animal tested positive were dropped from statistical analysis to reduce the risk of including false-positive herds in the statistical analyses.

There were 80 herds with one or more positive animals and 41 herds with no positive animals in the sample (66% herd-level prevalence). Twenty-six herds (21%) were dropped from further analyses because they had only one positive cow. Twelve herds (10%) were dropped from analysis because of missing data. The resulting sample used for statistical modeling included 46 positive herds and 37 negative herds (55% herd-level prevalence). A multi-variable logistic-regression model was used to evaluate the results. The variable ‘use of an exercise lot for lactating cows' was associated with a three-fold increase in odds of a herd being positive for M. paratuberculosis infection (O.R.=3.01, C.I.=1.03–8.80); ‘cleaning of maternity pens after each use' was associated with a three-fold reduction in odds of a herd being positive for M. paratuberculosis infection (O.R.=0.28, C.I.=0.08–0.89); ‘application of lime to pasture areas in 1993' resulted in a ten-fold decrease in odds of a herd being positive for M. paratuberculosis infection (O.R.=0.10, C.I.=0.02–0.56).     

Herd characteristics and management practices associated with seroprevalence of Mycobacterium avium subsp paratuberculosis infection in dairy herds

OBJECTIVE: To investigate herd characteristics and management practices associated with a high seroprevalence of Mycobacterium avium subsp paratuberculosis (MAP) in dairy herds in central California. SAMPLE POPULATION: 60 randomly selected cows from each of 21 dairy herds. PROCEDURES: Sera of selected cows were tested for antibodies against MAP by use of an ELISA test kit. Cows with a test sample-to-positive control sample (S:P) ratio of > or = 0.25 were considered seropositive, and herds with > or = 4% seropositive cows were considered high-seroprevalence herds. Data on herd characteristics and management practices were collected via interviews with owners. Bayesian logistic regression was used to model the predictive probability of a herd having a high seroprevalence on the basis of various herd characteristics and management practices. RESULTS: 9 of 21 (43%) herds were classified as high-seroprevalence herds. Five variables (history of previous signs of paratuberculosis in the herd, herd size, exposing cattle to water from manure storage lagoons, feeding unsalable milk to calves, and exposing heifers < or = 6 months old to manure of adult cows) were included in the predictive model on the basis of statistical and biological considerations. In large herds, the predictive probability of a high seroprevalence of MAP infection decreased from 0.74 to 0.39 when management changed from poor to good practices. In small herds, a similar decrease from 0.64 to 0.29 was predicted. CONCLUSIONS AND CLINICAL RELEVANCE: The seroprevalence of MAP infection in California dairies may be reduced by improvements in herd management practices.