Drinking water for dairy cattle: always a benefit or a microbiological risk?

Drinking water can be considered an essential nutrient for dairy cattle. However, because it comes from different sources, its chemical and microbiological quality does not always reach accepted standards. Moreover, water quality is not routinely assessed on dairy farms. The microecology of drinking water sources and distribution systems is rather complex and still not fully understood. Water quality is adversely affected by the formation of biofilms in distribution systems, which form a persistent reservoir for potentially pathogenic bacteria. Saprophytic microorganisms associated with such biofilms interact with organic and inorganic matter in water, with pathogens, and even with each other. In addition, the presence of biofilms in water distribution systems makes cleaning and disinfection difficult and sometimes impossible. This article describes the complex dynamics of microorganisms in water distribution systems. Water quality is diminished primarily as a result of faecal contamination and rarely as a result of putrefaction in water distribution systems. The design of such systems (with/ without anti-backflow valves and pressure) and the materials used (polyethylene enhances biofilm; stainless steel does not) affect the quality of water they provide. The best option is an open, funnel-shaped galvanized drinking trough, possibly with a pressure system, air inlet, and anti-backflow valves. A poor microbiological quality of drinking water may adversely affect feed intake, and herd health and productivity. In turn, public health may be affected because cattle can become a reservoir of microorganisms hazardous to humans, such as some strains of E. coli, Yersinia enterocolitica, and Campylobacter jejuni. A better understanding of the biological processes in water sources and distribution systems and of the viability of microorganisms in these systems may contribute to better advice on herd health and productivity at a farm level. Certain on-farm risk factors for water quality have been identified. A practical approach will facilitate the control and management of these risks, and thereby improve herd health and productivity.

[Changes in blood concentrations of bone-specific biomarkers, osteocalcin and C-telopeptide, in third or higher parity sows after administration of calcium and vitamin D]. / Verloop van de botspecifieke biomarkers osteocalcine en C-telopeptide in bloed van derde en oudere worps zeugen na gelijktijdige verstrekking van extra calcium en vitamine D.

Changes in blood concentrations of bone-specific biomarkers, osteocalcin and C-telopeptide, in third or higher parity sows after administration of calcium and vitamin D The study had two objectives: 1, to measure levels of two bone-specific biomarkers, with a view to identifying sows with leg problems; 2, to evaluate the effect of additional vitamin D/ monocalcium phosphate on the two bone-specific biomarkers and the number of stillborn piglets. Of 272 third or higher parity sows, 136 were randomly selected to receive a high dose (33 times the normal dose) of vitamin D (as depot) 1 to 5 days before parturition plus 20 g monocalcium phosphate 3 days before and 3 days after parturition. The sows in the control group received no treatment. The housing and feeding conditions of the two groups of sows were identical. Blood samples were taken from five sows per group just before parturition, 2-3 days after parturition, 3 weeks after parturition, and 1 week after weaning for the measurement of osteocalcin (bone formation, osteoblastic activity) and C-telopeptide (CTX, bone degradation, osteoclast activity), calcium, and phosphorus. The total number of piglets born, stillborn piglets, and weaned piglets were registered per group. The bone metabolism of sows is comparable with that of mice, sheep, and goats. CTX levels increased and osteocalcin levels decreased after parturition, and the reverse pattern was seen after weaning, with a decrease in CRX levels and an increase in osteocalcin levels. Thus these two bone-specific biomarkers can be used to monitor bone metabolism in sows. Serum calcium and CTX levels were clearly correlated. Blood calcium levels increased significantly after treatment with vitamin D/monocalcium phosphate in sows with low calcium levels at the start of the study but not in sows with normal calcium levels at the start of the study. Treatment with vitamin D/monocalcium phosphate did not influence the number of stillborn piglets or the number of weaned piglets.

[Selenium requirements of dairy goats]. / Seleenbehoefte van melkgevende geiten.

Selenium is an essential part of the enzyme glutathione-peroxidase (GSH-Px) and plays an important role in the intracellular aspecific immune defence. Reference values for blood levels of GSH-Px are not available for dairy goats. The EU has authorized the addition of selenium (as E), in the form of sodium selenite or sodium selenate, to animal feeds, to a maximum of 0.5 mg selenium/kg complete feed. Dairy goats given feed containing the maximum level of selenium (0.5 mg/kg) had GSH-Px levels of more than 1000 U/g Hb. The reference values for GSH-Px in cattle, horses, and pigs are between 120 and 600 U/g Hb. Newborn kids had GSH-Px levels between 350 and 400 U/g Hb, comparable with those ofnewborn calves. In conclusion, the addition of selenium to feeds for dairy goats in amounts authorized by the EU leads to blood GSH-Px levels that are substantially higher than those in other species, such as horses, cattle, and pigs. Thus the maximum level of supplemental selenium in feeds for dairy goats should be less than 0.5 mg/kg.

Analyses of the results of different test systems in the 2005 global proficiency testing schemes for infectious bursal disease virus and Newcastle disease virus antibody detection in chicken serum.

The results of global proficiency testing schemes (PTS) for serological tests to detect antibodies against infectious bursal disease virus (IBDV) and Newcastle disease virus (NDV) in chicken serum, in which 125 and 120 laboratories, respectively, participated from Africa, Asia, Europe, Central and South America, were used to analyse the performances of different antibody test systems such as virus neutralization tests, haemagglutination inhibition tests, enzyme-linked immunosorbent assays and agar gel precipitation tests. All laboratories were asked to carry out their routine diagnostic tests for the detection of IBDV and NDV antibodies as usual. This global ring trial provided a large amount of data on variation within and between laboratories and test systems used worldwide. The data showed that the variation between the quantitative test results of different laboratories (R(between)) using the IBDV virus neutralization tests and the NDV haemagglutination inhibition test was higher (about double) compared with the variation within commercial enzyme-linked immunosorbent assay systems. Although both tests are often referred to and used as the "gold standard" in experimental and scientific studies, official procedures and for the validation of tests, this study shows that there is an urgent need for a global implementation of recommended test procedures and/or the inclusion of international reference sera in these studies.

[Measurement of the status of trace elements in cattle using liver biopsy samples]. / Het bepalen van de status van de spoorelementenvoorziening bij rundvee met behulp van leverbiopten.

Serum, plasma, or urine samples are usually used for the measurement of the trace elements copper; zinc, iron, selenium, because these samples are easy to obtain; however; these samples are not always appropriate. For example, it is not possible to measure molybdenum, the major antagonist of copper; in blood or urine. Therefore measurement of trace elements in liver tissue is considered the gold standard. For the assessment of selenium the method of choice remains determination of glutathion peroxidase in erythrocytes and for the assessment of magnesium determination of magnesium in urine. We determined the accuracy and repeatability of measuring trace elements in liver biopsies and whole liver homogenates. The levels of trace elements measured were similar in both preparations (92% agreement). Liver biopsy in live animals is a relatively simple procedure but not common in The Netherlands. Reference levels of trace elements, classified as too low, low, adequate, high, and too high, were established on the basis of our research and information in the literature. In a second study we investigated the practical aspects of obtaining liver tissue samples and their use. Samples were collected from cattle on a commercial dairy farm. Liver biopsy provided additional information to that obtained from serum and urine samples. We prepared a biopsy protocol and a test package, which we tested on 14 farms where an imbalance of trace minerals was suspected. Biopsy samples taken from 4 to 6 animals revealed extreme levels of trace elements.

[Suckling calves with symptoms of swayback]. / Het beeld van swayback bij zoogkalveren.

Within a 1-year period, three calves from the same herd developed ataxia of the hind limbs and urinary incontinence at about 6 months of age. Signs progressed and the calves were slaughtered 1-8 months after the onset of signs. The calves belonged to a suckling beef herd of 35 cattle. Blood samples from 11 cattle of different ages were collected and glutathione peroxidase and copper levels were measured. Glutathione peroxidase levels were below the normal range in all cattle and copper levels were below the normal range in 7 of ll cattle. Pathological examination of an affected calf revealed a Wallerian type of degeneration of myelinated nerve fibres in the lateral and ventral spinal cord tracts. In addition, the hepatic copper content was very low. Copper deficiency is a well-known cause of swayback in young sheep and goats. To our knowledge, this is the first report of a possible association between a swayback-like syndrome and copper deficiency in calves.

Shortfalls using second-generation anticoagulant rodenticides.

Second-generation anticoagulant rodenticides can give rise to unexpected casualties in nontarget species in zoos. The first two offspring of a pair of turkey vultures (Cathartes aura) died of brodifacoum toxicosis. The adult birds fed rodenticide-killed mice to their offspring. There are previous case reports of small carnivorous birds (Dacelo novae-guinae and Tockus deckeni) killed eating poisoned (difenacoum and brodifacoum) mice. Even a granivorous species (Rollulus roulroul) died, probably by contamination of its food by cockroaches that transported the rodenticide.