Persistently infected animals (PI animals), that is those animals born after an intrauterine infection of the dam during the first 120 days of gestation, are the main source of bovine virus diarrhoea virus (BVD virus) in a cattle population. The success of any BVD virus eradication programme depends on the ability to detect all PI animals at a young age. The purpose of this study was to evaluate the use of the antigen ELISA test and the reverse transcriptase-polymerase chain reaction (RT-PCR) test for the diagnosis of PI animals in the presence of maternal antibodies, and to compare them with the classical virus isolation test. In this experiment, 25 calves born after an experimental infection with a mixture of BVD virus field strains were used. All calves were found to be positive for BVD virus using the virus isolation test, both before the ingestion of colostrum and again at 10 weeks of age. Both the virus isolation test and the antigen ELISA test were shown to be unreliable indicators for the diagnosis of persistent infections with BVD virus, when used in the presence of high levels of maternal antibodies. However, the RT-PCR test gave positive results even in the presence of high maternal antibody titres, indicating the suitability of the RT-PCR test for use in eradication programmes.

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.

A field study was performed with 218 dairy cows in nine dairy herds in order to investigate the prevalence of post partum fatty infiltration of the liver and its relationship to subsequent body condition scores, blood variables and milk production. The mean concentration of triacylglycerols in the liver was 61.2 mg/g wet liver tissue. The prevalence of fatty liver (more than 50 mg triacylglycerol in 1 g wet liver tissue) was 54.1%. Serum non-esterified fatty acids, urea and blood glucose concentrations appeared to be significant indicators of hepatic lipidosis between 6 and 17 days post partum (R2=0.33). High milk production and large losses of body condition score in early lactation were significant indicators of hepatic lipidosis from a retrospective point of view (R2=0.22). Single body condition scores were not significantly related to the concentration of triacylglycerol in the liver. It was concluded that, according to the classification used, fatty liver seems to be fairly common in early lactating dairy cows. Although correlation coefficients were too low to enable a precise and accurate description of liver triacylglycerol content, we found some biologically explicable variables in commercial herds that were significantly related to the liver triacylglycerol content.

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.

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.

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.

To test the safety of semen two approaches can be applied: checking the end product, or continuous surveillance of the bulls before and after semen production. The first method is examination of semen for the presence of infectious agents. This method depends completely on a single investigation and therefore relies only on the sensitivity of the test method. The second method is testing the bulls for diseases before and after semen collection, based on sequential investigations for the absence of either pathogens or antibodies against infectious agents. The EU-Directive 88/407 prescribes that bulls in AI stations must be monitored for the absence of diseases, but only at 12-monthly intervals, which is a severe disadvantage. Furthermore, the directive is specific neither in the tests to be carried out nor in the specification of some pathogens (e.g. Campylobacter foetus).A programme is presented based on monthly testing of a limited number of bulls for the absence of endemic diseases only, on the basis of Hazard Analysis of Critical Control Points (HACCP). This method only applies to diseases with high transmission rates. Testing some 20% of the animals on a monthly basis can monitor these highly contagious diseases (e.g. IBR). To monitor BVDv infections, however, monthly testing of all negative animals and semen culture or semen PCR of animals that have seroconverted for this virus seems necessary. Endemic diseases with slow transmission rates in bulls do not suit such a system and can only be monitored on an individual basis.

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.

Veterinary RecordVolume 145, Issue 9 p. 258-259 Short Communication Lack of clinical abnormalities in dairy heifers with low blood and liver copper levels Dr G. H. Wentink DVM, PhD, Dr G. H. Wentink DVM, PhD Department of Large Animal Medicine and Nutrition, Faculty of Veterinary Medicine, Utrecht University, PO Box 80. 152, 3508 TD, Utrecht, The NetherlandsSearch for more papers by this authorG. Smolders BSc, G. Smolders BSc Research Station for Cattle-, Sheep-, and Horsehusbandry, Lelystad, The NetherlandsSearch for more papers by this authorTj. Boxem BSc, Tj. Boxem BSc Research Station for Cattle-, Sheep-, and Horsehusbandry, Lelystad, The NetherlandsSearch for more papers by this authorTh. Wensing MSc, PhD, Th. Wensing MSc, PhD Department of Large Animal Medicine and Nutrition, Faculty of Veterinary Medicine, Utrecht University, PO Box 80. 152, 3508 TD, Utrecht, The NetherlandsSearch for more papers by this authorK. E. Müller DVM, PhD, K. E. Müller DVM, PhD Department of Large Animal Medicine and Nutrition, Faculty of Veterinary Medicine, Utrecht University, PO Box 80. 152, 3508 TD, Utrecht, The NetherlandsSearch for more papers by this authorA. M. van den Top DVM, PhD, A. M. van den Top DVM, PhD Department of Large Animal Medicine and Nutrition, Faculty of Veterinary Medicine, Utrecht University, PO Box 80. 152, 3508 TD, Utrecht, The NetherlandsSearch for more papers by this author Dr G. H. Wentink DVM, PhD, Dr G. H. Wentink DVM, PhD Department of Large Animal Medicine and Nutrition, Faculty of Veterinary Medicine, Utrecht University, PO Box 80. 152, 3508 TD, Utrecht, The NetherlandsSearch for more papers by this authorG. Smolders BSc, G. Smolders BSc Research Station for Cattle-, Sheep-, and Horsehusbandry, Lelystad, The NetherlandsSearch for more papers by this authorTj. Boxem BSc, Tj. Boxem BSc Research Station for Cattle-, Sheep-, and Horsehusbandry, Lelystad, The NetherlandsSearch for more papers by this authorTh. Wensing MSc, PhD, Th. Wensing MSc, PhD Department of Large Animal Medicine and Nutrition, Faculty of Veterinary Medicine, Utrecht University, PO Box 80. 152, 3508 TD, Utrecht, The NetherlandsSearch for more papers by this authorK. E. Müller DVM, PhD, K. E. Müller DVM, PhD Department of Large Animal Medicine and Nutrition, Faculty of Veterinary Medicine, Utrecht University, PO Box 80. 152, 3508 TD, Utrecht, The NetherlandsSearch for more papers by this authorA. M. van den Top DVM, PhD, A. M. van den Top DVM, PhD Department of Large Animal Medicine and Nutrition, Faculty of Veterinary Medicine, Utrecht University, PO Box 80. 152, 3508 TD, Utrecht, The NetherlandsSearch for more papers by this author First published: 28 August 1999 https://doi.org/10.1136/vr.145.9.258Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume145, Issue9August 1999Pages 258-259 RelatedInformation

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 l 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.

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.

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.

Hepatic lipidosis postpartum (pp) in high-producing dairy cows is associated with an increased vulnerability to infectious diseases, an increased frequency of metabolic diseases and substantial reproduction problems. To enable research that aims at elucidation of the relationship between the hepatic lipidosis postpartum on one hand and the aforementioned problems on the other, an animal model for hepatic lipidosis was developed. Using this model, evidence was found that the sudden and substantial increase of hepatic uptake of free fatty acids contributes to accumulation of triacyglycerol in the liver. As far as the increased susceptibility for infectious diseases is concerned, results were obtained that indicate that in cows with hepatic lipidosis, the immune response is suppressed. With respect to the fertility problems, with the help of in vitro tests, it was found that the quality of oocytes collected in cows with hepatic lipidosis 80–140 days postpartum was decreased.

The significance of beta2-integrins for the generation of antigen-specific immune responses in vivo was studied employing the bovine model of beta2-integrin deficiency. To that end four cattle with bovine leukocyte adhesion deficiency (BLAD) and healthy age-matched controls were immunized with tetanus toxoid (TT) and rabies virus (RV) vaccines three times in monthly intervals. In addition, two animals with BLAD and three controls received a fourth vaccination 8 months after the start of the study. Proliferative responses of peripheral blood mononuclear cells (PBMC) to the antigens TT and RV as well as specific serum immunoglobulin G (IgG) titers were determined in intervals for up to 10 months after primary vaccination. Proliferative responses of PBMC to TT and RV were substantially lower in cattle with BLAD than in controls, although PBMC from cattle with BLAD were shown to have the capacity to proliferate in the response to the mitogen concanavalin A. Occurrence of antigen-specific IgG titers was delayed and they were considerably lower in cattle with BLAD compared to controls. Finally, treatment of TT- and RV-stimulated PBMC from an immunized control with different concentrations of the anti-CD18 monoclonal antibody R15.7 resulted in a dose-dependent inhibition of lymphocyte proliferation to almost 100%. The results of the present study show that beta2-integrin deficiency leads to delayedand severely impaired immune responsiveness in vivo. The observations that antibody production, although considerably delayed and impaired, does occur and that apparently class-switching takes place in BLAD indicate T-cell reactivity in vivo.

We investigated the activities of hepatic glycerolipid synthesizing enzymes during postpartum fatty liver development in 10 high-producing dairy cows that had free access to feed during the dry period; a parallel group of 8 control cows was fed according to recommended energy requirements. After calving, both test and control cows had free access to feed. In the period of 10-14 wk before calving, voluntary dry matter intake of the test cows was 20.6 kg/d (SEM 0.42); the restricted control cows received 7 kg/d. Postpartum triacylglycerol concentrations in liver biopsies were one- to twofold higher in the test than in the control cows. The higher plasma nonesterified fatty acid (NEFA) concentrations after parturition in the test vs. the control group were probably caused by a more negative energy balance in the test cows, which was associated with a slightly lower postpartum dry matter intake. After calving, hepatic mitochondrial glycerolphosphate acyltransferase (GPAT) activities were significantly lower in the test than in the restricted control cows. A low GPAT activity may divert fatty acids from esterification to beta-oxidation to protect the hepatocytes against further accumulation of triacylglycerols. The activities of hepatic phosphatidate phosphohydrolase, diacylglycerol acyltransferase, and cholinephosphate cytidylyltransferase were not different in the two groups. This study indicates that in cows given free instead of restricted access to feed during the dry period have a postpartum hepatic triacylglycerol accumulation that is mainly determined by a raised hepatic uptake of plasma NEFA.

The effect of cobalt supplementation on the immune reactivity in vitamin B12 deficient lambs was measured by comparing the humoral and cell-mediated immune responses against bovine herpes virus type 1 and Mycobacterium paratuberculosis. In addition, faecal egg counts were performed after natural infection with gastrointestinal nematodes. The experiments were performed with registered Texel twin lambs of the same sex. One lamb of each twin received three cobalt pellets divided over the grazing period. The non-supplemented lambs had lower serum vitamin B12 levels than their supplemented brother or sister. Our results demonstrate significantly lower lymphoblastic responses against Mycobacterium paratuberculosis in non-supplemented lambs compared with supplemented lambs 4 weeks after paratuberculosis vaccination. Vitamin B12 deficient lambs in this study had significant higher faecal egg counts than their supplemented brother or sister after natural infection with gastrointestinal nematodes. No differences were found in total and differential white blood cell counts, in total protein, albumin, alpha-, beta- and gamma-globulin and in antibody production against bovine herpes virus type 1 and Mycobacterium paratuberculosis.

In this short review attention is focused on the occurrence of metabolic diseases in combination with disturbances of the immunologic response. Epidemiological surveys in cows suffering from hepatic lipidosis indicate an increased percentage of aspecific infectious diseases. Few experiments have been described in which immunoreactivity in cows with spontaneous or induced metabolic diseases were studied.The results reported in these studies indeed strongly suggest impairment of the immune response in metabolic diseases, but do not indicate a causative relationship between metabolism and immunity.