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 calf mortality in large Swedish dairy herds

The aim of this study was to identify possible risk factors for 1-90 day calf mortality in large Swedish dairy herds. Sixty herds with a herd size of ≥160 cows were visited once between December 2005 and March 2006. Thirty herds were known to have low mortality (LM) and 30 were known high mortality herds (HM). Upon the visit, data about housing and management was collected from interviews with personnel responsible for the calves. The herd status regarding the calves' passive transfer (total protein), levels of α-tocopherol, β-carotene and retinol, and excretion of faecal pathogens (Cryptosporidium spp., Escherichia coli F5, rota and corona virus) was evaluated based on targeted sampling of high risk calf groups; in each herd, blood and faecal samples were collected from calves 1-7 and 1-14 days old, respectively. Similarly, the herd status regarding clinical respiratory disease in calves and history of respiratory virus exposure was evaluated based on lung auscultations and blood samplings of calves 60-90 days old. The median calf mortality risk (in calves 1-90 days of age) among HM herds was 9% (Range: 6-24%) and among LM herds 1% (Range: 0-2%). LM and HM herds were compared using five logistic regression models, covering potential risk factors within different areas: "Disease susceptibility", "Factors affecting the gastrointestinal tract", "Factors related to transmission of infectious disease", "Hygiene" and "Labour management". The percentage of calves, 1-7 days old, with inadequate serum concentrations of α-tocopherol and β-carotene were significantly higher in HM herds compared to LM herds and also associated with higher odds of being a HM herd (OR=1.02; p=0.023 and OR=1.05; p=0.0028, respectively). The variable "Average number of faecal pathogens in the sampled target group" was significantly associated with higher odds of being a HM herd (OR=4.65; p=0.015), with a higher average in HM herds. The percentage of calves with diarrhoea treated with antibiotics was significantly higher in HM herds and was associated with higher odds of being a HM herd (OR=1.08; p=0.021). The median age at death of calves in the age interval 1-90 days that died during a one-year period was significantly lower among HM herds (13 days) than in LM herds (24 days) (p=0.0013) The results indicate that gastrointestinal disorders may be an important cause of calf mortality in large Swedish dairy herds. Furthermore, our study provides additional indications that fat soluble vitamins might play an important role for calf health.     

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.     

Risk factors associated with bovine tuberculosis in traditional cattle of the livestock/wildlife interface areas in the Kafue basin of Zambia

We conducted a cross-sectional study from August 2003 to February 2004 to identify risk factors for bovine tuberculosis (BTB) in the Kafue basin of Zambia. We investigated a total of 106 herds of cattle for presence of BTB using the comparative intradermal tuberculin test (CITT) while an interviewer-administered questionnaire was used to gather epidemiological data on herd structure, management and grazing strategies. BTB prevalence at herd level was estimated and possible risk factors were investigated using the multiple logistic regression model. The true herd level prevalence of BTB was estimated at 49.8% (95% CI: 37.9, 61.7%). The logistic regression model showed that cattle herd BTB status was highly associated with area and husbandry practices. When compared to Kazungula, cattle herds in Blue Lagoon were more likely to test positive for BTB when other factors such as management practices were controlled (OR=10.5). In terms of grazing strategies, transhumant herds (TH) had higher odds (OR=3.0) of being positive compared to sedentary herds (OR=1.0). The results in this study provide preliminary information about potential risk factors that were found to be associated with BTB status in cattle.     

Risk factors for Brucella spp. infection In dairy cattle farms in Asmara, State of Eritrea

A cross-sectional study was conducted to identify risk factors for herd infection by Brucella spp. in dairy cattle in the suburbs of Asmara, Eritrea. Data were collected from 64 herds, randomly selected from a total of 99 herds with a minimum herd size of 9 cows. A questionnaire was used to gather data on management, hygiene and herd structure. Serum samples collected from all pregnant heifers, cows and bulls, were screened for Brucella infection by the Rose Bengal test (RBT), and all RBT-positive sera re-tested with the complement-fixation test (CFT) for confirmation. A seropositive herd was defined as one in which at least one animal tested positive in the CFT. There were 23 (36%) positive herds among the 64 studied. Both multiple logistic and multiple betabinomial regression modeling were used to analyze the data. Mixed-breed herds, compared to single (exotic)-breed herds, were found to be independently associated with increased herd seroprevalence (OR=5.2, 95% confidence interval 1.4–18.7) in the multiple logistic model with the herd infection status as the dependent variable. The importance of this variable was supported by the multiple betabinomial regression model (OR=3.3, 1.4–7.6) with animal-level prevalence within herd as the outcome variable. Both models also revealed the presence of a negative association between seropositivity and cattle stocking density.     

Risk factors for epidemic respiratory disease in Norwegian cattle herds

An epidemic of acute respiratory disease associated with bovine respiratory syncytial virus (BRSV) occurred during the winter and spring of 1995 in two neighbouring veterinary districts in the south-eastern part of Norway.The objective of this study was to describe the time course of the outbreak associated with BRSV in the cattle herds, and to determine the association between selected herd factors and the risk of experiencing a herd outbreak of acute respiratory disease.Data from 431 cattle herds on the dates of disease occurrence, location of the farms, herd size, age profile and production type were collected retrospectively for 1995. The risk of acute respiratory disease occurring in a cattle herd was related to the herd size as well as the type of production, with an expressed interaction between these two variables. From the Cox proportional-hazards model, the risk of a herd outbreak in a mixed herd of 20 animals was estimated to be 1.7-times greater than in a dairy herd and 3.3-times greater than a beef herd (reference category) of a comparable size. On increasing the herd size to 50 animals, the risk increased 1.3-fold for a mixed herd, 3.3-fold for a dairy herd, and 2.1-fold for a beef herd, compared to the risk for a corresponding type of herd of 20 animals.     

Risk factors for the between-herd spread of Mycobacterium bovis in Canadian cattle and cervids between 1985 and 1994.

Microorganisms of the genus Mycobacterium cause tuberculosis in many animal species including humans. Generally, Mycobacterium bovis (M. bovis) infects cattle and cervids, but it has the potential to infect virtually all species of mammals. This study examined and analysed the data from the nine outbreaks of tuberculosis in Canadian cattle and cervids from 1985 to 1994. For the purposes of this study, a positive herd was one with at least one culture-positive animal. A reactor herd had at least one animal which was positive or suspicious on a mid-cervical, comparative cervical, or gross or histopathologic test for tuberculosis. Herd classification was either reactor/positive or negative. Data for the study were collected from the outbreak records in the Regional or District offices of Agriculture and Agri-Food Canada. Logistic regression was used to study spread of tuberculosis between herds. Two risk factors were identified: increasing herd size; and, the reason why a herd was investigated as part of the outbreak. This latter factor was interpreted as a surrogate measure for the nature of contact between the study herd and other potentially infected herds in the outbreak. Increasing herd size was associated with an increased risk of being positive for tuberculosis with herds of 16-35, 36-80, and >80 animals having odds ratios of 2.9, 5.8, and 9.3, respectively, when compared to a herd size of <16 animals (p < 0.001). When compared to perimeter testing (i.e. testing herds within a specified radius of an infected herd), all other reasons for investigation had higher odds ratios (p < 0.001). These odds ratios were 57.8 for traceout herds (i.e. herds which had purchased animal(s) from a reactor/positive herd), 31.8 for herds with pasture or fence-line contact with a reactor/positive herd, and 14.9 for traceback herds (i.e. herds which had been a source of animals for reactor/positive herd(s)).     

Herd factors associated with the seroprevalences of four major respiratory pathogens in slaughter pigs from farrow-to-finish pig herds

The objective of this study was to investigate sero-epidemiological aspects of Mycoplasma hyopneumoniae (Mh), influenza H1N1 and H3N2 viruses and Aujeszky disease virus (ADV) in fattening pigs from 150 randomly selected farrow-to-finish pig herds. Different herd factors were examined as potential risk indicators for the percentage of pigs with antibodies against the 4 pathogens. The median within-herd seroprevalences of the pathogens were: Mh 76%, H1N1 100%, H3N2 40% and ADV 53%. There was a positive association between the seroprevalences of both influenza viruses, and a negative association between the seroprevalences of ADV and H1N1. The percentage of pigs seropositive for Mh increased with the purchase of gilts and with the season (slaughter date in March-April). The within-herd seroprevalences of both influenza viruses were higher in the case of a higher density of pig herds in the municipality. A higher number of fattening pigs per pen additionally increased the risk of being seropositive for H3N2. The percentage of pigs with anti-gE-antibodies against the wild type ADV increased with higher airspace stocking density in the finishing unit, increasing herd size, increasing number of pig herds in the municipality and slaughter date in March-April. Increased seroprevalences for these 4 respiratory pathogens were mostly associated with pig density in the herd and its vicinity, the winter period, and with the purchase of gilts. Purchase of gilts, number of fattening pigs per pen and airspace stocking density are risk factors that can be managed directly by farmers striving to attain a high respiratory health status of pigs.     

Risk factors associated with the presence of viable Listeria monocytogenes in bulk tank milk from US dairies

The objective of the study was to screen a large number of herd management practices and herd characteristics from US dairies to identify herd-level risk factors associated with the presence of Listeria monocytogenes in bulk tank milk (BTM). A total of 71 variables was univariately evaluated for their association with the presence of L. monocytogenes in BTM. Results from the univariate analysis indicated that using automatic take offs and having an open herd management increased the risk of BTM contamination with L. monocytogenes, while storing manure in outside pens not accessible to cattle decreased the risk. These variables, however, were not sustained in the multivariable model, which indicated that the presence of L. monocytogenes in BTM was significantly associated with region of the country (farms in the southeast and northeast were six and four times more likely respectively, to have BTM contamination than farms in the west) and number of milking cows (herds with >500 milking cows were five times more likely to have BTM contamination than herds with <100 milking cows). In conclusion, our results suggest that risk factors associated with BTM contamination are different depending on the geographical region and herd size of the operation.     

A case-control study of Nocardia mastitis in Nova Scotia dairy herds

A case-control study was conducted to identify herd production, housing, and hygienic and therapeutic factors associated with a diagnosis of Nocardia mastitis in dairy herds in Nova Scotia. The data were collected by on-farm interviews with owners of 54 case and 54 control herds.

Logistic regression was used to study risk factors. The use of dry cow products containing neomycin, including two specific dry cow products, was strongly associated with a diagnosis of Nocardia mastitis in a herd. Other factors which increased the risk of Nocardia mastitis were higher levels of production, larger herd size, and a large percentage of cows treated with dry cow products. These results are compared to results from a similar study carried out in Ontario.

     

Risk factors for bovine herpesvirus-1 seropositivity

This paper reports the investigation of risk factors for bovine herpesvirus-1-seropositivity, based on a cluster-sample survey of the Belgian cattle population. This serosurvey was carried out in 1998 in 309 randomly selected unvaccinated herds of all types (dairy, mixed and beef) were all bovids (N = 11,284) were sampled.

Older and male cattle had higher seroprevalence. Origin (homebred or purchased) and herd size interacted; for smaller herds (≤50 cattle on the premises), purchase status and larger herd size were risk factors, whereas these effects were not observed for larger herds.     

The consequences of risk-based surveillance: Developing output-based standards for surveillance to demonstrate freedom from disease

Risk factors associated with high or low long-term incidence of displaced abomasum (DA) or clinical ketosis were studied in 60 Swedish dairy herds, using multivariable logistic regression modelling. Forty high-incidence herds were included as cases and 20 low-incidence herds as controls. Incidence rates were calculated based on veterinary records of clinical diagnoses. During the 3-year period preceding the herd classification, herds with a high incidence had a disease incidence of DA or clinical ketosis above the 3rd quartile in a national database for disease recordings. Control herds had no cows with DA or clinical ketosis. All herds were visited during the housing period and herdsmen were interviewed about management routines, housing, feeding, milk yield, and herd health. Target groups were heifers in late gestation, dry cows, and cows in early lactation. Univariable logistic regression was used to screen for factors associated with being a high-incidence herd. A multivariable logistic regression model was built using stepwise regression. A higher maximum daily milk yield in multiparous cows and a large herd size (p = 0.054 and p = 0.066, respectively) tended to be associated with being a high-incidence herd. Not cleaning the heifer feeding platform daily increased the odds of having a high-incidence herd twelvefold (p < 0.01). Keeping cows in only one group in the dry period increased the odds of having a high incidence herd eightfold (p = 0.03). Herd size was confounded with housing system. Housing system was therefore added to the final logistic regression model. In conclusion, a large herd size, a high maximum daily milk yield, keeping dry cows in one group, and not cleaning the feeding platform daily appear to be important risk factors for a high incidence of DA or clinical ketosis in Swedish dairy herds. These results confirm the importance of housing, management and feeding in the prevention of metabolic disorders in dairy cows around parturition and in early lactation.     

A case-control study on the association of selected risk factors with the occurrence of bovine tuberculosis in the Republic of Ireland

We did a case-control study on the association between the occurrence of bovine tuberculosis in herds in the East Offaly area and a number of possible risk factors: herd size, the purchasing of cattle, the herd history, the status of contiguous herds, distance to the nearest badger sett, and animal factors such as age, breed and animal type. The characteristics of 100 herds that had a confirmed outbreak of tuberculosis at a herd test in 1988 were compared with those from an equal number of herds that passed at least one tuberculin test during that year. The study base consisted of 1379 herds mainly from the eastern part of County Offaly. The data were analysed at both herd and animal levels. Factors that were associated with an increased risk of tuberculosis breakdowns at the herd level were (i) the total number of animals in the herd and (ii) the restriction of a contiguous herd for tuberculosis within a period of 6 months prior to or following the herd under study. A number of factors were associated with an animal having an increased risk of failing a tuberculin test. After adjusting for all other variables in the model, cows, heifers and bullocks were 10.3, 14.8 and 8.0 times, respectively, more likely to fail a tuberculin test than calves. Cattle that had teen purchased since the previous herd test were less likely to fail a tuberculin test compared with cattle that had been present at the time of the preceding herd test.     

Prevalence of fecal shedding of Salmonella spp in dairy herds

OBJECTIVE: To estimate prevalence of Salmonella spp in Ohio dairy farms and to identify potential risk factors for fecal shedding of salmonellae. DESIGN: Cross-sectional study. SAMPLE POPULATION: 105 Ohio dairy farms. PROCEDURE: Individual fecal samples from all mature cows in study herds were tested for Salmonella spp by use of standard bacteriologic culture procedures. Herds were identified as infected if at least 1 cow was shedding Salmonella spp. Information regarding herd characteristics, management practices, and health history were collected. Potential risk factors for herd-level Salmonella infection were identified. RESULTS: In 31% of the study herds (95% confidence interval, 22 to 40%), at least 1 cow was shedding Salmonella spp. Six percent of 7,776 fecal samples contained Salmonella organisms; prevalence within infected herds ranged from < 1 to 97%. Herd size, use of free stalls for lactating and nonlactating cows, and use of straw bedding in nonlactating cows were significantly associated with fecal shedding of Salmonella spp, as determined by use of univariate analysis. By use of multivariate analysis, large herds were more likely to be infected than smaller herds; however, no other factors were associated with Salmonella infection after adjustment for herd size. CONCLUSIONS AND CLINICAL RELEVANCE: Subclinical shedding of Salmonella spp is common in Ohio dairy herds, although we could not identify specific interventions that may influence the prevalence of Salmonella spp on dairy farms. It appears that large herd size and intensive management may provide an environment conducive to Salmonella shedding and chronic dairy herd infection.     

Neighbourhood infections of classical swine fever during the 1997-1998 epidemic in The Netherlands

Data of the 1997–1998 epidemic of classical swine fever (CSF) in The Netherlands were analysed in survival analysis to identify risk factors that were associated with the rate of neighbourhood infections. The study population consisted of herds within 1000 m of exclusively one previously infected herd. Dates of virus introduction into herds were drawn randomly from estimated probability distributions per herd of possible weeks of virus introduction. (To confirm the insensitivity of the results for this random data-selection procedure, the procedure was repeated 9 times (resulting in 10 different datasets).) The dataset had 906 non-infected and 59 infected neighbour herds, which were distributed over 215 different neighbourhoods. Neighbour herds that never became infected were right-censored at the last date of the infectious period of the infected source herd. Neighbour herds that became empty within the infectious period or within the following 21 days due to preventive depopulation or due to the implemented buying-out programme were right-censored 21 days before the moment of becoming empty. This was done as a correction for the time a herd could be infected without being noticed as such.

The median time to identified infection of neighbour herds was 2 weeks, whereas the median time to right censoring of non-infected neighbour herds was 3 weeks. The risk factors, radial distance ≤500 m, cattle present on source herd and increasing herd size of the neighbour herd were associated multivariably with the hazard for neighbour herds to become infected. We did not find an association between time down wind and infection risk for neighbour herds. Radial dispersion of CSFV seemed more important in neighbourhood infections than dispersion along the road on which the infected source herd is situated. The results of this study support the strategy of preventive depopulation in the neighbourhood of an infected herd. Recommendations are presented to adapt the applied control strategy for neighbourhood infections.     

Herd management practices associated with paratuberculosis seroprevalence in Dutch dairy herds

We describe the paratuberculosis management practices applied in dairy herds in the Netherlands. The findings from paratuberculosis seronegative and seropositive herds were compared to discover possible risk factors. In total, 370 randomly selected herds with > or =20 dairy cows were surveyed. A questionnaire was used to collect data on current and previous paratuberculosis management practices. All cattle aged > or =3 years were serologically tested for paratuberculosis using an enzyme-linked immunosorbent assay. Herds with >33 tested cattle, of which only one was seropositive, were excluded to reduce the risk of including false-positive herds in the analysis. A comparison of the management data of the seronegative herds (n = 166) and the seropositive herds (n = 143) showed that in both groups important management measures for the prevention of paratuberculosis, such as calving in a cleaned calving area, removing the calf immediately after birth, and feeding paratuberculosis non-suspect roughage to calves, were used only rarely. However, such measures should be regarded as the critical first step to control the disease and/or reduce its prevalence. Using univariable analysis, four factors were statistically different between seronegative and seropositive herds: herd size, cows with clinical signs of paratuberculosis, prompt selling of clinically diseased cattle and feeding milk replacer. Using a multivariable logistic regression model, only herd size was a significantly different factor. These results indicate that most of the paratuberculosis preventive management measures were executed on these Dutch dairy farms only to a limited extent.     

Associations between the proportion of Salmonella seropositive slaughter pigs and the presence of herd level risk factors for introduction and transmission of Salmonella in 34 Danish organic, outdoor (non-organic) and indoor finishing-pig farms

This paper evaluates the association between herd level risk factors for introduction and transmission of Salmonella in farms with three different production systems: organic, outdoor (non-organic) and indoor finishing-pig farms, and the presence of seropositive animals in the herds. Potential risk factors for Salmonella in the three pig production systems were identified through a literature review, and management information as well as serological data were collected in 34 pig farms: 11 organic farms, 12 outdoor farms, and 11 indoor farms. There were no general differences in the proportion of Salmonella seropositive animals in the organic, outdoor, and indoor pig farms. Correspondence analysis showed that the occurrence of seropositive animals in the herds was mostly associated to the risk of introducing Salmonella in the herds by purchasing and transporting growing pigs. No associations between herd risk factors for transmission and survival of Salmonella and seropositive animals in the herds were found.     

Characterization of Minnesota dairy herds participating in a Johne's disease control program and evaluation of the program risk assessment tool

The objectives of this study were to: (1) characterize Minnesota dairy herds participating in a Johne's disease control program (JDCP) based on herd size, milk production, and clinical Johne's disease (JD) history, (2) evaluate if change in farm management practices, expressed in risk assessment (RA) total score, is associated with the change between the first and most recent ELISA test herd seroprevalence or change in clinical JD culling rate, and (3) identify farm factors associated with ELISA seroprevalence. A total of 1234 RA, performed between January 2000 and February 2004, were available for analysis from 714 dairy herds. ELISA test results from herd sampling between 2000 and 2004 were obtained from the Minnesota board of animal health (MBAH) database, and were available for 474 herds. Both the first and the most recent ELISA test results for herds with more than one RA were available for 262 herds. Mean herd size and mean annual milk production per cow was higher in JDCP dairy herds (161 milking cows) than either all Minnesota dairy herds or Minnesota dairy herd improvement association (DHIA) herds. For herds with more than one RA available, the most recent RA total score was significantly lower (mean 11% less) than the first. The change in RA total score (and any RA subtotal scores) between the first and most recent RA was not associated with the change between the first and the most recent ELISA within-herd seroprevalence or the change in JD culling rate between the first and most recent RA. The most recent ELISA test results were positively associated with postweaned heifer score and JD culling rate. The RA score was not found to be an effective tool for the prediction of ELISA seroprevalence.     

Use of herd information for predicting Salmonella status in pig herds

Salmonella surveillance-and-control programs in pigs are highly resource demanding, so alternative cost-effective approaches are desirable. The aim of this study was to develop and evaluate a tool for predicting the Salmonella test status in pig herds based on herd information collected from 108 industrial farrow-to-finish pig herds in Portugal. A questionnaire including known risk factors for Salmonella was used. A factor analysis model was developed to identify relevant factors that were then tested for association with Salmonella status. Three factors were identified and labelled: general biosecurity (factor 1), herd size (factor 2) and sanitary gap implementation (factor 3). Based on the loadings in factor 1 and factor 3, herds were classified according to their biosecurity practices. In total, 59% of the herds had a good level of biosecurity (interpreted as a loading below zero in factor 1) and 37% of the farms had good biosecurity and implemented sanitary gap (loading below zero in factor 1 and loading above zero in factor 3). This implied that they, among other things, implemented preventive measures for visitors and workers entering the herd, controlled biological vectors, had hygiene procedures in place, water quality assessment, and sanitary gap in the fattening and growing sections. In total, 50 herds were tested for Salmonella. Logistic regression analysis showed that factor 1 was significantly associated with Salmonella test status (P = 0.04). Herds with poor biosecurity had a higher probability of testing Salmonella positive compared with herds with good biosecurity. This study shows the potential for using herd information to classify herds according to their Salmonella status in the absence of good testing options. The method might be used as a potentially cost-effective tool for future development of risk-based approaches to surveillance, targeting interventions to high-risk herds or differentiating sampling strategies in herds with different levels of infection.