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Biomedical subjects

G H Wentink

Publications and source records attributed to G H Wentink.

At least 19 recordsLinked to original sources
PubMed2002

Failure of foetal protection after vaccination against an experimental infection with bovine virus diarrhea virus.

A protocol is described to measure the protection of the bovine fetus against an experimental bovine virus diarrhea virus (BVDV) infection after vaccination. Two inactivated experimental vaccines were applied twice with a 3 week interval. A mixture of three different Dutch field strains was used as challenge on mainly the 82nd day of gestation to vaccinated and unvaccinated control animals. The challenge was applied 5 months after completion of the two-fold vaccinations. All calves born from unvaccinated control animals were persistently infected. The calves born from dams vaccinated with the two different inactivated BVDV vaccines were persistently infected in 78 and 60%, respectively.

Animals↗
PubMed2001

[Chronic wasting?].

Explore the source record for details and available documents.

Animal Husbandry↗
PubMed2001

Developments in veterinary herd health programmes on dairy farms: a review.

This review article addresses some major developments in herd health programmes for dairy farms over the last decades. It focuses particularly on herd health and production management programmes that use protocols and monitoring activities. The article further emphasizes the need for merging herd health programmes with quantitative epidemiological principles and methods. Subsequently, this article points to the latest developments regarding quality assurance in the dairy sector and some quality management methods. Quality should be regarded in its broadest sense. The importance of integrating veterinary herd health programmes and quality (risk) management support at a dairy farm level is stressed. Examples are provided.

Animal Husbandry↗
PubMed2000

Relationships between fatty liver and fertility and some periparturient diseases in commercial Dutch dairy herds.

Declining fertility in dairy cows is frequently suggested to arise from the occurrence of a more negative energy balance and/or the concomitant increased accumulation of triacylglycerol in the liver. Therefore, we performed a field study to assess the clinical effects of postpartum fatty liver in dairy cows on fertility and reproductive disease. Data were collected from 360 cows from nine dairy herds on fertility, diseases, and the liver triacylglycerol content on two occasions during lactation: 6 to 17 days and 38 to 50 days postpartum. The mean concentration of triacylglycerol in the liver was 54.6 mg/g from 6 to 17 days and 38.4 mg/g from 38 to 50 days postpartum. The probability of pregnancy was 30% lower for cows with higher contents of triacylglycerol in the liver compared to the probability for cows with low liver triacylglycerol (P = 0.049). The probability of estrus was also 35% lower for the cows with high triacylglycerol in the liver. This resulted in larger intervals between parturition and first heat and parturition and pregnancy for these cows. There was no effect observed on the first insemination conception rate. Given a certain level of triacylglycerol, recorded milk production had a positive effect on time to pregnancy. The incidences of endometritis, lochiometra and cystic ovarian follicles were not higher in cows with higher liver triacylglycerol contents. Endometritis was associated with a lower first insemination conception rate and more days open (chi2 = 4.26, P = 0.03 and T-test = -2.02, P= 0.04 respectively). We concluded that our results support the idea that differences in the negative energy balance or the accumulation of triacylglycerol in the liver of postpartum dairy cows affect fertility performance. The data also indicate that an increase in milk production has no negative impact on fertility as long as the amount of triacylglycerol in the liver remains the same.

Animals↗
PubMed2000

Using serum amyloid A to screen dairy cows for sub-clinical inflammation.

In this study, 232 lactating dairy cows from six herds were observed for clinical signs of inflammation and simultaneously had blood samples drawn to determine whether or not Serum Amyloid A (SAA) was present. Serum protein electrophoresis and white blood cell differential count revealed inflammation in SAA+ samples but not in SAA-samples. Using positive SAA test results as the standard for presence of inflammation, clinical findings consistent with inflammation concurred with positive SAA results only 26% of the time (p<.001) while the lack of clinical signs consistent with inflammation concurred with negative SAA results 95% of the time (p<.001). There was also a significant difference (p<.005) in management styles in that cows permanently fed on wilted/cured forages and kept inside had a 26% prevalence of positive SAA blood samples whereas the overall prevalence of SAA+ samples was 16%. These findings indicate that whole herd screening using SAA can be of value to the veterinarian in helping to identify cows with inflammatory diseases. From a public health perspective, SAA testing of cows going to market can help differentiate those not needing intensive inspection from those that do.

Acute-Phase Reaction↗
PubMed2000

Genetic variation of susceptibility to Mycobacterium avium subsp. paratuberculosis infection in dairy cattle.

Paratuberculosis is an infectious disease that is not easily amenable to classical control methods such as treatment and vaccination. Experimental animal models suggest that there could be genetic factors responsible for susceptibility or resistance to infection with the causative agent, Mycobacterium avium subsp. paratuberculosis. The aim of this study was to estimate genetic variation in susceptibility to paratuberculosis in Dutch dairy cattle. Data collected during a vaccination trial, conducted from 1984 to 1994, was used. A total of 3020 cows, with complete pedigree records and infection status at slaughter, were available for analysis. A standard polygenic statistical probit model was used to estimate heritabilities. The estimated heritability of susceptibility to M. avium. subsp. paratuberculosis infection was 0.06 for the overall population. In the subpopulation of vaccinated animals the estimated heritability was 0.09. Other calculations based on the model used in this study argue against a prominent role for vertical transmission. Because the establishment of genetic variation is one of the first steps towards the exploration of the possible use of selection for genetic improvement, the present study provides evidence for the presence of genetic variation in the susceptibility of cattle to paratuberculosis. Because the economic impact of the disease is substantial, the development and application of genetic tools, along with other control methods, could be instrumental in the eradication of paratuberculosis.

Animals↗
PubMed1999

Reduced lymphoid response to skin allotransplants in cows with hepatic lipidosis.

The immune responsiveness of cows with hepatic lipidosis (fatty liver) in comparison to control cows with a normal liver fat content was tested by applying skin allotransplants to the skin of the back of cows on day 3 after parturition. Immunoreactivity was determined by semiquantitative counting of the number of infiltrating lymphocytes in the recipient skin adjacent to the allotransplants during a period of 21 days. There were more invading lymphocytes in samples from control cows than there were in samples from cows with hepatic lipidosis. It was concluded that cows with hepatic lipidosis have a reduced lymphoid response to skin allotransplants.

Animals↗
PubMed1999

Congress report on progress in pestivirus virology.

This mini-review highlights new information on various research aspects presented by specialists from all over the world at the 4th Pestivirus meeting held in Giessen (Germany) from March 15-19, 1999. Especial attention is paid towards differences in humeral and cellular immune response of naive and persistently infected calves with BVDV, and towards BVD eradication programmes in the Scandinavian countries. The development of techniques for an early diagnosis of CSF in live pigs and the progress on both sub-unit and MLV marker vaccines against this disease are reported.

Animals↗
PubMed1998

The immune response of cattle, persistently infected with noncytopathic BVDV, after superinfection with antigenically semi-homologous cytopathic BVDV.

Cattle persistently infected (PI) with noncytopathic (ncp) bovine virus diarrhea virus (BVDV) are at risk for developing fatal mucosal disease (MD), which is considered to occur after superinfection with antigenically homologous cytopathic (cp) BVDV. In this study, we intranasally inoculated four PI-animals, that were PI with 2 ncp BVDV strains with 10(5) TCID50 antigenically closely related cp BVDV. Two PI-animals were inoculated with 10(5) TCID50 ncp BVDV and one PI-animal, with virus free cell culture medium. Two out of four PI-animals that were inoculated with cp BVDV, developed MD and were euthanized at day 17 and at day 24 after infection. Postmortem, both animals showed typical lesions of MD and cp BVDV was isolated. The other two PI-animals that were inoculated with cp BVDV did not develop MD and were euthanized at day 51. They showed ulcerations in the gastrointestinal tract, cp BVDV was isolated and neutralizing antibodies were detected. From the three PI-animals, that were inoculated with ncp BVDV or cell culture medium, cp BVDV was also isolated. Cross neutralization tests were performed and no antigenic differences could be detected between the cp strains isolated from the PI-animals. Lymphocyte subsets of these PI-animals were determined by flow cytometric analysis. Before superinfection, the percentages of gamma delta subsets were much higher in the PI-animals that did not develop MD than in nonviremic control animals and in the PI-animals that died of MD. From this study we conclude that the presence of antigenically closely related cp BVDV in PI-animals does not necessarily lead to the development of MD and that besides the antigenic relatedness between the persisting ncp BVDV and cp BVDV other factors, for instance the number of circulating gamma delta cells, might determine whether or not PI-animals develop MD.

Animals↗
PubMed1998

Milk production and reproduction during a subclinical bovine herpesvirus 1 infection on a dairy farm.

This study describes an outbreak of bovine herpesvirus 1 (BHV1) infections in a dairy herd with special reference to disease symptoms, reproductive performance and milk production losses. The study was carried out with a dairy herd consisting of 98 lactating animals. All animals were housed in the same freestall barn with intensive contact between all animals. An outbreak of BHV1 was induced by injecting three seropositive cows with dexamethasone. During the outbreak, no clinical signs were observed in any of the newly infected animals. At the time of infection, a significant drop in milk production was noted in animals that were initially-seronegative. The production loss was estimated at approximately 9.5 1 per infected animal during the infectious period of 14 days. None of the pregnant cows aborted because of BHV1 infection. During 50 days before BHV1 circulation, there was a significant decrease in the number of successful inseminations in both seronegative and seropositive animals. Therefore, it is doubtful that early pregnancies were terminated by BHV1 infection. The proportion of successful inseminations during the BHV1 circulation in this herd, and in the period thereafter, did not significantly differ from the baseline period.

Abortion, Veterinary↗
PubMed1998

Evaluation of a milk test for detection of subclinical ketosis.

This study included 190 lactating cows from eight dairy farms and was designed to investigate the sensitivity and specificity of a milk test (Ketolac) for detecting subclinical ketosis in dairy cattle. Blood and milk samples were collected between 38 and 50 days post partum. At a beta-hydroxybutyric acid concentration in blood of 1.2 mmol/L, the prevalence of ketosis was 14%. A Response Operator Characteristic curve was drawn for two milk test values: 100 mumol/L and 200 mumol/L. Assessment of several beta-hydroxybutyric acid cut-off values in blood showed that when 100 mumol/L on the Ketolac milk test was defined positive, the most desirable sensitivity-specificity combination was achieved. This milk test can be routinely used to screen a herd for subclinical ketosis.

Animals↗
PubMed1997

Sheep do not have a major role in bovine herpesvirus 1 transmission.

With regard to BHV1 eradication programs in cattle it is important to know whether sheep can be a reservoir of BHV1. We therefore performed an experiment that consisted of three phases. In phase 1, 10 sheep were inoculated with high doses of BHV1 and kept in close contact with 5 sheep and 5 calves. All inoculated sheep excreted BHV1 between 8 and 15 days post inoculation and seroconverted. Although BHV1 was isolated from the nasal mucosa of 3 out of 5 sentinel sheep, none of the sentinel sheep produced antibodies against BHV1. One sentinel calf excreted BHV1 through days 12-17; the remaining 4 calves excreted BHV1 between days 18 and 24 suggesting that the first calf was infected by sheep and the remaining 4 sentinel calves were infected by that calf and not by sheep. The bacic reproduction ratio (R0) of BHV1 between sheep and calves was estimated at 0.1, and among calves it was estimated at > or = 9. In phase 2, all inoculated sheep were treated with dexamethasone and kept in close contact with 5 sheep and 5 calves. All dexamethasone treated sheep re-excreted BHV1 over a 6- to 9-day period. None of the sentinel animals seroconverted. In phase 3, the sentinel sheep and calves of phase 1 were kept in two groups and were treated with dexamethasone. None of the sentinel sheep re-excreted BHV1, whereas 3 out of 5 sentinel calves did. It is concluded that while BHV1 infection in sheep is possible, BHV1 does not spread from sheep easily to cattle.

Animals↗
PubMed1997

Impaired specific immunoreactivity in cows with hepatic lipidosis.

In this study, hepatic lipidosis in cows was experimentally induced by offering an energy surplus during the dry period. Liver triacylglycerol (TAG) was 16% in the experimental group. In the control group fed the same diet in restricted quantities, liver TAG was about 7%. The animals of both groups were vaccinated with tetanus vaccine at Day 3 after parturition. It was demonstrated that the cows with high liver TAG percentages had lower humoral and cellular (P < 0.05) immunological responses compared with the animals with low liver TAG levels at Day 14 after vaccination. The results obtained in the high TAG group support the notion that the frequent occurrence of aspecific infections in cows with hepatic lipidosis may be due to impaired immunoreactivity.

Animals↗