Search

This article discusses risk analysis of infectious diseases in a cattle population. Heck cattle living in nature reserve 'De Oostvaardersplassen' were studied as an example of the risk analysis approach. Twenty-five adult cattle were tested for every infectious disease agent that the risk analysis indicated might be prevalent. All sampled cattle tested positive for Bovine Herpesvirus 1, whereas the prevalence of antibodies against other infectious disease agents was below the level that was assumed to be the threshold for spread of the disease to cattle in the surrounding areas. Risk management of infectious diseases was expressed in a so-called 'low-risk profile'. The risk of introduction or spread of infectious diseases was estimated to be very low as long as the population was kept strictly enclosed.

In addition, it is relevant to know to what extent milk production data can provide information about hyperketonaemia. In 12 selected herds, milk samples were collected from 114 cows that had been lactating for maximally 70 days. During regular milk testing, two additional milk samples were taken to assess the 'Nitroprusside test' and the 'Ketolac BHB' test. After collection of milk samples, blood samples were taken to measure serum beta-hydroxybutyric acid. The prevalence of hyperketonaemia appeared to vary between herds from 1 to 9 per 10 lactating cows. The sensitivity of the Nitroprusside test was higher than the sensitivity of the Ketolac BHB test at threshold values of beta-HBA > 1.5 mmol/l. The Ketolac BHB test in comparison to the Nitroprusside test appeared to provide a smaller chance of false-positive test results at a given level of sensitivity. The serum beta-hydroxybutyric acid concentration was correlated with milk yield/day and the milk fat concentration of an individual cow.

The choice of dry cow antibiotics should be based on clinical efficacy studies. The choice also depends on the sensitivity pattern of S. aureus, and the expected length of the dry period. There are many quarter, cow and herd factors that influence efficacy of dry cow therapy. These factors include somatic cell count, front-versus-hind quarter, age, and the number of infected quarters in a cow. Nutrition of cows at the end of the lactation and hygienic conditions on the farm and off are also important. The effect of extra treatments at dry off are questionable.

This study evaluated the reliability of making bacteriological cultures of composite milk samples for the diagnosis of subclinical udder infections in dairy herds. Quarter samples as well as composite samples were collected from 482 cows with suspected subclinical mastitis from 69 Dutch dairy farms. The samples were used to measured somatic cell counts and to prepare bacteriological cultures. The sensitivity and specificity of the bacteriological cultures of the composite samples were compared with those of the quarter samples. The sensitivity of Staphylococcus aureus, Streptococcus uberis, Streptococcus agalactiae and Streptococcus dysgalactiae was 57.9%, 65.2%, 86.6%, and 60.3%, respectively. The specificity was higher than 98% for all four bacteria. Although information is lost when composite samples are used, composite samples are useful, especially for large dairy herds. The advantage and disadvantages of the use of composite samples are discussed.

Postmilking teat disinfection is accepted as an important part of standard preventive measures against mastitis in dairy cattle. The efficacy of postmilking teat disinfection against infections with contagious pathogens such as Staphylococcus aureus and Streptococcus agalactiae is beyond doubt. However, the efficacy of teat disinfection against infections with environmental pathogens such as Escherichia coli is disputed, and a negative effect has even been described in some situations. This article reviews the practice of teat disinfection in dairy cattle. Premilking and postmilking teat disinfection are discussed, as is the efficacy, different ways of teat disinfection, and different disinfectants. It is concluded that post-milking teat disinfection is an effective management measure in most herds. Selection of teat disinfectants should be based on proven efficacy, which is required for registration of the preparation as a veterinary medical product in the Netherlands.

In this review a number of the main epidemiological developments in the field of udder health in the Netherlands are summarized. The changes considering the bulk milk somatic cell count are described, as are the population dynamics of subclinical mastitis. Additionally, clinical mastitis caused by Escherichia coli and Staphylococcus aureus and their risk factors are reviewed. Finally, some future developments and the possible applications of these developments are discussed.

In this paper the developments in the field of bovine herd health and production management are illustrated. The current use of herd health and production management methods in veterinary practices are illustrated, and a uniform concept for execution of herd health and production management programs is given. The expected future developments and the critical points in these developments are discussed. The changing role of the veterinarian in bovine practice with the application of herd health is outlined.

As no systematic study has been done to get an accurate estimate of the incidence of return to oestrus after first insemination in sows in the Netherlands, the objectives of this investigation were: 1) to obtain an estimate of the incidence of return to oestrus after insemination at the herd level; 2) to investigate the association between incidence of return to oestrus after first insemination and reproduction characteristics to get an impression of the economic importance. These objectives were investigated using the reproduction results of 240 swine breeding herds in The Southern Netherlands in 1987, using their CBK plus computerized herd management records. The average incidence of return to oestrus after first insemination on a herd level was 16.9 per 100 first inseminations. An increase of incidence with 10 returns per 100 first inseminations, corrected for confounders in a multiple linear regression model, was associated with a decrease of approximately 0.3 liveborn piglets/sow/year. Thereupon individual sows were followed in 1988 and 1989 prospectively in 37 sow herds from weaning to insemination, returning to oestrus or not after first insemination to farrowing. The investigation focused in particular on the relationship between returning to oestrus after first insemination and incident infection with porcine parvovirus (PPV) and Leptospira interrogans serovar bratislava (L. bratislava). During a number of consecutive farm visits sows were blood sampled at weaning and again a blood sample was taken 6 weeks later. The final dataset that was analysed consisted of 161 animals that did not return to oestrus after first insemination and 158 animals that returned to oestrus after first insemination.(ABSTRACT TRUNCATED AT 250 WORDS)

The diagnoses Porcine Epidemic Abortion and Respiratory Syndrome (PEARS)-positive and PEARS-negative can be made using the following data on herd performance: the average number of stillborn piglets per litter, the average number of live piglets per litter and the average piglet mortality before weaning. Depending on the number of litters used in calculating the averages, the extent to which two out of the three performance data should deviate to arrive at the diagnosis PEARS-positive is given in tables and figures. The same farm will only be diagnosed PEARS-negative if after some time at least two out of the three performance data deviate less than other criteria also provided in tables and figures.

This review paper is concerned with antibacterial therapy of mastitis caused by Escherichia coli. The choice of an antibacterial agent is discussed, and nine criteria are referred to, on which this choice should be based. In the second part possible forms of antibacterial treatment are discussed. Literature on parenteral and local treatment of mastitis due to E. coli is scarcely available. The evaluation of antibacterial drugs is mainly based on MIC values and pharmacokinetic studies in normal animals. Unfortunately, results of clinical trials are hardly available. Today combinations of trimethoprim/sulphonamide apparently are the best available choice for the parenteral treatment of mastitis caused by E. coli. Infusion of polymyxins or gentamycin is discussed as a method of intramammary therapy.

The pathogenesis, course run by the disease, and symptomatic treatment of mastitis due to Escherichia coli in dairy cattle are reviewed in relation to the functioning of cellular and humoral defence mechanisms. The systemic symptoms of disease during mastitis caused by E. coli are attributed to the release and subsequent absorption from the udder of endogenous inflammatory mediators, rather than the direct absorption of endotoxins into the circulation. The course run by the disease during mastitis due to E. coli varies considerably. Reasons for these variations include genetic variation, stage of lactation and the function of humoral and cellular defence mechanisms.

The technique of epidural anaesthesia is described in the present paper. In addition, the relationship between external features and the dosage of the local anaesthetic was studied. In this study, epidurography was used to visualise the cranial extension of the anaesthetic solution in the vertebral canal. It is concluded that the most reliable parameter is the length of the spinal column. Cases in which the use of epidural anaesthesia is indicated, are stated.

Treatment of a lesion of the teats not associated with perforation of the teat canal or teat cistern is discussed in the present paper. Treatment of the lesion of the teats using a Bykanula is compared with temporary drying off of the involved quarter. In eleven out of the twenty cases reported, the process of healing was complicated by mastitis in the involved quarter. When the outlet of the teat was involved in the lesion, this complication was likely to be 5.4 times larger than it was when the teat opening was not involved. In the 'temporary drying-off group', the complicating mastitis was a reason for culling the animal within six months after treatment had been initiated in five out of nine cases. On the other hand treatment of the complicating mastitis in the 'Bykanula-group' was successful in every case. Problems in carrying out this clinical trial are also discussed.

The diagnostic aspects, incidence, risk factors and prevention of coliform mastitis are reviewed in the present paper. It is concluded that it is not possible to establish an accurate diagnosis of coliform mastitis, which is based on a specific clinical symptom differentiating it from other forms of mastitis. Not any single symptom or combination of symptoms is specific for coliform mastitis. The importance of coliform mastitis in dairy cattle showed a marked increase during the last few decades. Successful programmes for the prevention of mastitis reduced the importance of contagious organisms, but the overall incidence of mastitis has remained unchanged; therefore, the proportion of cases of coliform mastitis increased. The observation that coliform micro-organisms are common bacteria causing mastitis in herds with low bulk milk somatic cell counts implies that the future of the dairy industry will be associated with particular risks. Factors involving the risk of coliform mastitis are divided into cow level factors and herd level factors. The most important cow level factors were: leaking milk in between milkings, lesions of the teats and a reduced capacity of the immune system. Risk factors on the herd level include: the bedding material, the design of cubicles, exposure to daylight in summer-time, exposure to dirt and the use of dry-cow therapy. The possible role of antibiotic dry-cow treatment and teat dipping in colonisation resistance is discussed. Preventive programmes designed to reduce the incidence of coliform mastitis have not been very successful so far.