Epidemiological and genetical studies in Norwegian pig herds. II. Overall disease incidence and seasonal variation

The present epidemiological study is based on individual health records from 1984 to 1986 in 70 pig herds in the south-eastern part of Norway. For most of the recorded diseases, the incidence rate was less than 1% per farrowing. The majority of disease recordings concerned 6 frequently-occurring conditions; the MMA-syndrome, mastitis, metritis, neonatal diarhoea, arthritis and scrotal hernia. A seasonal effect on the incidence rate was shown for several diseases. The incidence rate for the MMA-syndrome of about 17.5% seems to be of the highest recorded for this disease in a population study.     

"Benchmark" - a large observational study of Ontario beef breeding herds: Study design and collection of data

The methods used in a large field study which investigated the health and productivity of Ontario beef breeding herds are described. Beginning in the calving season of 1986, 180 breeding herds on 170 randomly sampled farms were followed for a two year period, using producer records and annual farm visits.

The response (cooperation) rate among the eligible producers initially contacted was 70%. Approximately two-thirds of producers maintained individual animal records, primarily calving season records. Approximately 40% recorded disease occurrences.

The advantages, disadvantages, and interpretation of “on-farm” observational studies are discussed.

     

Epidemiological and genetical studies in Norwegian pig herds. III. Herd effects

Herd differences in disease incidence in 70 Norwegian pig herds were assessed by health card registrations. Such differences proved to be considerable. The incidence of the MMA-syndrome, mastitis, metritis and neonatal diarrhoea was higher in herds producing only weaners ("weaner herds") than in herds with combined production. The mean disease incidence in herds providing breeding stock for the Norwegian Pig Breeders' Association ("breeding herds") was at the same level as in ordinary combined production herds. There was no consistent relationship between changes in disease incidence and herd size, though the incidence of the MMA-syndrome was lower in the largest herds.     

Persistent fecal Salmonella shedding in five dairy herds

OBJECTIVE: To monitor patterns of Salmonella fecal shedding in naturally infected dairy herds, determine the association between fecal shedding and individual animal production measures, and evaluate potential risk factors for shedding of Salmonella organisms among cattle in dairy herds. DESIGN: Longitudinal study. SAMPLE POPULATION: 5 Ohio dairy herds. PROCEDURE: For 3 herds, fecal samples were collected from all mature cows and unweaned calves 7 times during an 18-month period. For the remaining 2 herds, fecal samples were collected from 50 lactating cows 6 times during a 12-month period. Individual animal production records for 3 herds were used to examine associations between individual fecal Salmonella shedding status and 305-day mature-equivalent milk production, somatic cell count, milk fat content, and milk protein content. Multivariable logistic regression was used to test for associations between fecal shedding status and breed, lactation status, lactation number, and duration of lactation. RESULTS: None of the adult animals had clinical signs of salmonellosis, but prevalence of fecal Salmonella shedding at individual collection times ranged from 0 to 99% for cows and from 0 to 67% for unweaned calves. Mature cows were more likely to be shedding Salmonella organisms than were unweaned calves. Within herds, lactation status and duration of lactation for individual animals were associated with Salmonella shedding status. Salmonella fecal shedding status was not associated with individual cow production measures. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that subclinical fecal Salmonella shedding can persist in dairy herds for up to 18 months with no measurable effects on health or production of individual cows.     

Blood selenium associated with health and fertility in Norwegian dairy herds

A survey of blood selenium (Se) concentrations in Norwegian Red heifers and dry period cows was conducted to reveal possible association to management, feeding, health and fertility. Selenium contents were determined in 254 herd blood samples consisting of pooled samples from individual non-lactating animals from herds in 5 counties. The Se concentrations showed a normal distribution with mean 0.09 microg Se/g blood, with a standard deviation (SD) of 0.05, and ranged from 0.02 to 0.23 microg/g, with 50 % of the samples being between 0.06 and 0.11 microg/g. The herds with Se concentrations below 0.06 microg/g were smaller (21.4 +/- 8.7 cow-years) than those with Se levels above 0.11 microg/g (27.5 +/- 14.1 cow-years) (P<0.01), but there were no differences in milk yield, incidence of replacement, proportion of animal culling, amount of concentrate or grass silage as percentage of energy consumption between the groups. Treatment registration records showed a tendency that more animals in the low Se herds were treated for all the diseases included in this investigation (64.8 animals per 100 cow-years) than those in the high Se herds (57.5 per 100 cow-years), while no such differences were revealed for individual disorders. There was, however, a significant difference in bulk milk somatic cell counts (BMSCC) between low and high Se herds, their values being 137 000 and 155 000 cells/ml, respectively. This difference was significantly influenced by herd size. Furthermore, a total of 4916 lactations were analyzed from individual health and fertility recordings, including 2 934 first lactations and 1 982 later lactations. The present study revealed a reduced incidence of disease treatment with increased Se concentrations from 0.02 to 0.23 microg Se/g blood. In this regard, there seemed to be an optimum of 0.10 to 0.15 microg Se/g for all types of mastitis treatments summarized, and for treatment of retained placenta. Thus, herd Se concentrations below and above these values was connected with increased probability for sum mastitis and retained placenta, reflecting the effect of the quadratic term of Se. The cow (composite) milk somatic cell count (SCC) was lower in lactations from low Se herds than in high Se herds with a marked SCC increase in the Se concentration interval from 0.11-0.13 microg/g blood. In conclusion, heifers and dry period cows in Norway are low in blood Se content and there seems to be a positive association between increased blood Se concentration pre partum and decreased incidence of mastitis, ovarian cysts and anoestrus/silent oestrus post partum.     

The effects of calving to first service interval on reproductive performance in normal cows and cows with postpartal disease

The relationships between the calving to first service interval and several measures of reproductive performance were evaluated in 1738 lactation records from cows in 32 southern Ontario Holstein herds. Lactation records were divided into three mutually exclusive health categories based on the cows' postpartal disease histories.

Relationships between the calving to first service interval and the first service conception rate, number of services per conception and open interval were similar for all three health categories. The first service conception rate was lower and the average number of services per conception higher in cows first bred before 60 days when compared to cows first bred after 60 days. The relationship between the calving to first service interval and the open interval indicated that for each day that breeding was delayed the open interval was extended by 0.86 days.

It appeared that overall conception rates may be lower for cows first bred very early or very late, but differences in the overall conception rate were only significant for cows experiencing a reproductive tract infection. Unless very expensive semen is being used, it is suggested that disease free cows be bred at the first heat occurring after 40 days postpartum, and that cows experiencing postpartal disease be bred at the first heat occurring after 60 days postpartum.

     

Leptospirosis: I. Clinical investigation of the infection in dairy cattle in the Waikato district of New Zealand

An investigation was made into the prevalence of leptospiral infection in cattle. An area 50 km radius was selected in a region where leptospirosis was reputedly common. Farmers volunteered 250 herds with 39 500 cows for testing and 7 500 animals were selected and sampled. Twenty-nine cows (0.4%) on 14 (5.6%) of the farms had leptospiruria at the first examination. Leptospirae were cultured from the urines of nine of these animals and all were Leptospira interrogans serovar hardjo. Serologically 12.5% of cows had titres of 1:200 or greater to hardjo and 3.5% titres of 1:200 or greater to pomona. In the Spring of 1977, there was evidence of clinical leptospirosis in calves associated with only one of the herds and no clinical leptospirosis in the 250 lactating herds, although leptospiral titres were found in 88% of them. This indicated that clinical disease was much less common than infection. We concluded that leptospirosis was of minor economic importance in dairy cattle, although it could be significant in individual herds, and a health hazard to farm workers.     

Respiratory disease markers in porcine bronchoalveolar lavage fluid

In bronchoalveolar lavage fluid (BALF) of pigs originating from different herds bacteria, cells and the antibacterial peptide PR-39 were examined to gain information about the lung health status. In a high health nucleus herd 56% and in low health herds 20-100% of the examined pigs were found positive for potentially pathogenic bacteria. Based on these findings, a novel definition for bacterial respiratory tract disease was established using an 8% cut-off for the relative number of neutrophils in bronchoscopic and a 40% cut-off in transtracheal BALF in combination with the occurrence of potentially pathogenic microorganisms. The antibacterial peptide PR-39 was highly correlated to this definition of respiratory disease. An assessment of the bacteriological respiratory health status appears to be possibly based on the determination of PR-39 concentrations in BALF using different cut-off values according to the lavage method (2.5 nM for bronchoscopic and 5 nM for transtracheal BALF).     

Tramped teats--clinical mastitis disease complex in tied cows. Environmental risk factors and interrelationships with other diseases

The effects of stall length, manure system, type of bedding and calving disorders on incidence rates of tramped teats, udder injuries, and clinical mastitis in Swedish Red and White tied cows, as well as interrelationships between these 3 disorders were investigated. Data used consisted of 370 herds, for a total of 45,133 cow records. Cows in herds with liquid manure system were at higher risk of udder injuries and mastitis than in herds with solid system. Lower risk of both udder injuries and mastitis was found for cows in herds with short stall size (less than 180 cm) compared to herds with stalls of 205-219 cm length. It was suggested that other factors, such as slipperiness of the stall floor and presence and type of feeding barrier, must be considered when the effect of stall characteristics on tramped teats is investigated. In farms with solid manure system cut straw or sawdust bedding increased the risk of tramped teats and mastitis relative to uncut straw. Parity and calving disorders were important risk factors for udder health and their effect was greater in herds with liquid manure system. Tramped teats and udder injuries were the most serious risk factors for clinical mastitis.     

Virological and serological studies on the role of PI-3 virus, BRSV, BVDV and BHV-1 on respiratory infections of cattle. I. The detection of etiological agents by direct immunofluorescence technique

Nasal cells extracted from nasal swabs obtained from 95 cattle with signs of respiratory disease, out of eleven different herds, were tested for BHV-1, PI-3 virus, BRSV and BVDV using direct immunofluorescence technique. Viral antigen positive samples were detected in seven out of eleven herds examined. Of the 95 individual diseased cattle, 19 were found positive for at least one viral antigen. It was found that especially BHV-1 and PI-3 virus are important causative agents in cattle respiratory disease, both or in combination with other pathogenic agents. Multiple infection in virologically positive herds were observed in six (9.8%) of 61 animals tested. The findings reveal that single or multiple infections of selected viruses may be present in an important range in cattle and that direct immunofluorescence technique as a rapid method, based on the detection of viral antigen in nasal swab samples, is useful to establish the viral aetiology of acute bovine respiratory disease caused by these viruses, particularly in the diagnosis of mixed viral infections.     

Mycobacterium avium ssp. paratuberculosis--combined serological testing and classification of individual animals and herds

Several serological tests for detection of antibodies to Mycobacterium avium ssp. paratuberculosis, which is the causative agent of Johne's disease are validated, some of which are available commercially. These tests differ in sensitivity and specificity. Test results reported to farmers or veterinarians are therefore dependent upon the test in use. In the present study, three commercially available tests are used to test 2748 bovine sera from 119 Bavarian herds serologically. Serological results are compared with individual animals and on herd level. A scheme for serological testing and classification of herds as well as of individual animals based on a combination of serological test results is proposed.     

Leptospirosis: I. Clinical investigation of the infection in dairy cattle in the Waikato district of New Zealand

An investigation was made into the prevalence of leptospiral infection in cattle. An area 50 km radius was selected in a region where leptospirosis was reputedly common. Farmers volunteered 250 herds with 39 500 cows for testing and 7 500 animals were selected and sampled. Twenty-nine cows (0.4%) on 14 (5.6%) of the farms had leptospiruria at the first examination. Leptospirae were cultured from the urines of nine of these animals and all were Leptospira interrogans serovar hardjo. Serologically 12.5% of cows had titres of 1:200 or greater to hardjo and 3.5% titres of 1:200 or greater to pomona. In the Spring of 1977, there was evidence of clinical leptospirosis in calves associated with only one of the herds and no clinical leptospirosis in the 250 lactating herds, although leptospiral titres were found in 88% of them. This indicated that clinical disease was much less common than infection. We concluded that leptospirosis was of minor economic importance in dairy cattle, although it could be significant in individual herds, and a health hazard to farm workers.     

Estimated within-herd prevalence (WHP) of Mycobacterium avium subsp. paratuberculosis in a sample of Minnesota dairy herds using bacterial culture of pooled fecal samples

The objective of this study was to describe the estimated within-herd prevalence (WHP) of Mycobacterium avium subsp. paratuberculosis (Map) in a sample of infected dairy herds in Minnesota (N = 66) using test results from bacterial culture of pooled fecal samples. Fecal samples were collected from up to 100 cows in each herd and were tested using bacterial culture in pools of 5 cows based on age order. The mean herd size was 222 (44 to 1500) milking cows; the cows were predominantly Holstein. Using a frequentist approach, the within-herd mean individual fecal prevalence was 10% [95% confidence interval (CI) = 4% to 16%] assuming 70% test sensitivity and 99.5% test specificity. Using Bayesian methods, the estimated true within-herd individual cow prevalence was 14% (95% CI = 7% to 27%). Within-herd prevalence was higher in larger dairy herds than in herds with fewer cows. As Map is the causative agent of Johne's disease (JD), the results of this study could contribute to the success of a nationwide control program for this disease.     

Associations between health and productivity in cow-calf beef herds and persistent infection with bovine viral diarrhea virus, antibodies against bovine viral diarrhea virus, or antibodies against infectious bovine rhinotracheitis virus in calves

OBJECTIVE: To measure associations between health and productivity in cow-calf beef herds and persistent infection with bovine viral diarrhea virus (BVDV), antibodies against BVDV, or antibodies against infectious bovine rhinotracheitis (IBR) virus in calves. ANIMALS: 1,782 calves from 61 beef herds. PROCEDURES: Calf serum samples were analyzed at weaning for antibodies against type 1 and type 2 BVDV and IBR virus. Skin biopsy specimens from 5,704 weaned calves were tested immunohistochemically to identify persistently infected (PI) calves. Herd production records and individual calf treatment and weaning weight records were collected. RESULTS: There was no association between the proportion of calves with antibodies against BVDV or IBR virus and herd prevalence of abortion, stillbirth, calf death, or nonpregnancy. Calf death risk was higher in herds in which a PI calf was detected, and PI calves were more likely to be treated and typically weighed substantially less than herdmates at weaning. Calves with high antibody titers suggesting exposure to BVDV typically weighed less than calves that had no evidence of exposure. CONCLUSIONS AND CLINICAL RELEVANCE: BVDV infection, as indicated by the presence of PI calves and serologic evidence of infection in weaned calves, appeared to have the most substantial effect on productivity because of higher calf death risk and treatment risk and lower calf weaning weight.     

The use of test day models with small size of contemporary groups

For many years genetic evaluation of dairy cattle has been based on the analysis of 305-day lactation milk production. Thus, to account for environmental variance, records are usually grouped in herd–year–season (HYS) classes. The 305-day milk yield is computed on the basis of single test day records. An alternative approach to genetic evaluation is an analysis of individual test day records (P tak and S chaeffer 1993). A complete set of records contains more information than 305-day milk yield, and, in consequence, by including the single herd–test date (HTD) effect, this approach leads to an improvement in the accuracy of genetic evaluation. Modeling the time–herd effect in this way reduces residual variance. In populations with a small herd size a number of records with no contemporaries in HTD classes could appear. It should be noted that accurate estimation and prediction in mixed linear models requires both model adequacy and respective data structure. Unfortunately, inclusion of a HTD effect when herds are small (typical situation for European cattle breeding) causes a decomposition of data structure (more unbalanced experimental design). Hence, a modification to the grouping of the records was recommended (S walve 1995; S trabel 1997). When a lactation model is used various modifications to HYS definition could be implemented to improve its adjustment to environmental effects (S chmitz et al. 1991; S trandberg and G randinson 1997; C rump et al. 1997). The definition of herd–test day class is so precise that it does not allow for a different assignment of records to classes. What could be done is to combine HTD classes within the herd by joining the consecutive records (S walve 1995) or across herds looking for records from ‘similar’ herds taken at ‘similar’ periods of time (S trabel 1997). HTD effect can also be set as random to avoid the loss of information especially when the number of single HTD classes is high (R eents et al. 1995; P& ouml ; s & ouml ; et al. 1996). Finally, the HTD effect can be replaced by HYS, typical for the traditional model (P tak and ?arnecki 1998). The objective of the present study was to compare animal model evaluations using test day (TD) models with different definitions of contemporary groups (CG). Evaluations based on the 305-day lactation model were also carried out.     

Mycobacterium avium ssp. paratuberculosis – Combined Serological Testing and Classification of Individual Animals and Herds

Several serological tests for detection of antibodies to Mycobacterium avium ssp. paratuberculosis, which is the causative agent of Johne's disease are validated, some of which are available commercially. These tests differ in sensitivity and specificity. Test results reported to farmers or veterinarians are therefore dependent upon the test in use. In the present study, three commercially available tests are used to test 2748 bovine sera from 119 Bavarian herds serologically. Serological results are compared with individual animals and on herd level. A scheme for serological testing and classification of herds as well as of individual animals based on a combination of serological test results is proposed.     

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.     

Corynebacterium pseudotuberculosis infection in goats. II. The prevalence of caseous lymphadenitis in 36 goat herds in Northern Norway

The precalen-ce of caseous lymphadenitis was surveyed in 36 goat herds in Northern Norway. In each herd, information concerning the occurrence of the disease was obtained from the farmer. Adult animals (1 year of age or older) in 35 herds were examined for superficial swellings, and serum samples were collected from most animals in the herds. The sera were examined for antibodies to Corynebacterium pseudotuber-culosis using the bacterial agglutination test (BAT) and the hemolysis inhibition test (HIT).Gaseous lymphadenitis was diagnosed with certainty in 19 herds. Information from the farmers indicated that the disease indeed oc-curred in these herds, and that the majority had been infected with the disease for many years. The herds had apparently become infected through contact with animals from infected herds. Clinical examina-tions were carried out in 18 of these herds and superficial swellings were found in 26 % of the examined animals. The prevalence of ani-mals with lesions varied from 11 to 40 % among the herds. Of the animals in these herds, 81 % were positive in BAT and 84 % in HIT. The prevalence of positive animals varied from 26 to 99 % in BAT and 28 to 99 % in HIT. The prevalence of seropositive animals was lowest in a herd in which animals were kept separately in stalls.Caseous lymphadenitis could not be diagnosed in 16 herds. In-formation from the farmers indicated that the disease indeed seemed to be absent in 14 of these herds. These 14 herds had no history of contact with animals from herds considered to be infected. However, in the remaining 2 herds, the farmers were somewhat uncertain about the occurrence of the disease. One of these 2 herds had a history of contact with infected herds through participation in a goat “breeding circle”. Only a few of the animals were, however, seropositive and all these had low antibody titres.In 1 newly established herd, a single animal showed a high posi-tive titre in BAT only. All the other animals were negative in both tests. This particular herd consisted of animals obtained both from herds with caseous lymphadenitis and from herds in which the disease was not considered to occur.     

Annual costs associated with disease incidence and prevention in Colorado cow-calf herds participating in rounds 2 and 3 of the National Animal Health Monitoring System from 1986 to 1988

Thirty-nine and 47 randomly selected Colorado cow-calf operations were monitored for health events and their associated costs during rounds 2 and 3, respectively, of the National Animal Health Monitoring System (NAHMS). Data were collected from each operation for a one-year period by NAHMS veterinarians through monthly interviews, and the costs associated with the incidence and prevention of disease conditions were determined and expressed on a per cow basis. The beef producers involved in this study spent an average of $32.75 per cow in round 2 and $40.97 per cow in round 3 on an annual basis for the treatment of disease conditions. These costs were not different between the 2 rounds because of the wide ranges in the individual herd costs for disease incidence in each round. In both years of the study, the largest contributor to the total mean annual cost of disease incidence was the cost of death of diseased animals, and this cost accounted for approximately two-thirds of the total mean annual cost in each round. The total mean annual costs of disease prevention in these herds were $11.24 and $11.19 per cow in rounds 2 and 3, respectively. There were wide ranges in both rounds in the amounts of money spent per cow by individual herds for disease prevention. The largest individual cost of disease prevention in each year was the cost of vaccines/drugs, whereas the smallest individual cost in each round was the cost of veterinary services.(ABSTRACT TRUNCATED AT 250 WORDS)