[Detection of hyperketonemia with the aid of monitoring milk production and two milk tests]. / Detectie van hyperketonemie met behulp van beoordeling van de melkproductie en twee melktesten.

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.

[I&R (identification and registration) system cattle: an analysis of its use during a foot-and-mouth-disease outbreak in The Netherlands]. / I&R-systeem rund: een analyse ten behoeve van het gebruik tijdens een mond- en klauwzeer-uitbraak in Nederland.

The performance of the Dutch cattle I&R system was analysed, with emphasis on the potential use of the system for the control of an outbreak of foot and mouth disease (FMD). The analysis showed that not all mutations were centrally registered within the three working days that are allowed to pass between the actual change and the obligatory report. In particular, young calves and cattle heading for slaughter were reported too late. During an outbreak of FMD, the best strategy to trace animals off a farm seems to be first to identify all animals on the farm, using a preprocessed list of the animals that should be present on the farm according to the I&R system. Then all the animals that have left the farm during the last month can be traced in the central I&R computer or by asking the person to whom the farmer sold the cattle (the next owner). In the present study, 54% of the animals were localized within one day, and 94% within one week. Finally, some suggestions for improvement for the system are given.

Use of composite milk samples for diagnosis of Staphylococcus aureus mastitis in dairy cattle.

OBJECTIVE: To measure relative sensitivity and relative specificity for use of composite milk samples, compared with that of individual gland milk samples, for diagnosis of Staphylococcus aureus mastitis. ANIMALS: 505 cows suspected of having subclinical mastitis. Of these cows, 172 were considered infected with Sta aureus, based on the results from individual gland samples. PROCEDURE: Composite and individual gland milk samples were collected from cows suspected of having subclinical mastitis, and results of bacteriologic culturing of samples from the same cow were compared. Results were interpreted at the cow level. Relative sensitivity and relative specificity for composite samples were computed from 2 x 2 tables, using results from individual gland samples as references. RESULTS: Relative sensitivity for use of composite milk samples in diagnosing Sta aureus mastitis was 0.63. The relative specificity was 0.98. Factors influencing the relative sensitivity for composite samples were the number of infected glands per cow, the amount of Sta aureus shedding from infected glands, and the proportion of the composite milk obtained from each gland. CLINICAL IMPLICATIONS: Collecting composite instead of individual gland milk samples increases the number of false-negative results in diagnosing Sta aureus mastitis. By collecting consecutive samples from the same cow or by increasing the inoculum volume at culturing, this problem can be diminished.

[Testing area Wehl: study of risks of contacts in behalf of foot-and-mouth disease]. / Proefgebied Wehl: onderzoek naar risico's van contacten ten behoeve van mond- en klauw-zeerbestrijding.

A study on contacts between livestock holdings was conducted in a geographically defined area of 4 by 6 km in the Netherlands. The farmers were asked to record all contact on and off farm during a period of 2 weeks. The number of contacts in the 2 week period was high, on average 91.8 contacts per farm. The risk of spreading foot-and-mouth disease on or off the farm was greater for cattle farms than for swine farms. Relatively more people had contact with the animals while visiting cattle farms, thereby causing the higher risk. Most contacts occurred over short distances. Almost 50% of the contacts were within the research area. This finding confirms the importance of restricted areas around farms with foot-and-mouth disease infections.

[Reliability of bacteriological studies of composite samples in the diagnosis of subclinical udder infections in cattle]. / De betrouwbaarheid van het bacteriologisch onderzoek van mengmonsters voor de diagnose van subklinische uierinfecties bij rundvee.

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.