Chimeric (marker) C-strain viruses induce clinical protection against virulent classical swine fever virus (CSFV) and reduce transmission of CSFV between vaccinated pigs.

Two live recombinant vaccines (Flc9 and Flc11) against classical swine fever (CSF) were evaluated for their capacity to reduce transmission of virulent CSF virus (CSFV) among vaccinated pigs. In Flc9 the 5' terminal half of the E2 gene of the C-strain, a CSFV vaccine strain, was exchanged with the homologous gene of the bovine viral diarrhoea virus (BVDV) strain 5250, the E(rns) gene was exchanged likewise in the chimeric Flc11 virus. Both recombinant vaccines induce an antibody response in pigs that can be distinguished from that induced after a wild-type CSFV infection.

Llama heavy-chain V regions consist of at least four distinct subfamilies revealing novel sequence features.

In addition to conventional antibodies (Abs), camelids possess Abs consisting of only heavy chains. The variable domain of such a heavy-chain Ab (VHH) is fully capable of antigen (Ag) binding. Earlier analysis of 47 VHHs showed sequence features unique to VHH domains.

Environmentally regulated genes of Streptococcus suis: identification by the use of iron-restricted conditions in vitro and by experimental infection of piglets.

The identification of environmentally regulated genes of Streptococcus suis by the use of iron-restricted conditions in vitro and by experimental infection of piglets is described. Eighteen unique iron-restriction-induced (iri) genes and 22 unique in-vivo-selected (ivs) genes of Strep. suis were found.

Instrumental colour classification of veal carcasses.

Three experiments, involving over 56 000 veal carcasses, were carried out to develop a method for instrumental colour classification of veal carcasses at 45 min post mortem with the Minolta CR300. The method should produce results similar to those of the 10-point colour-system, which is currently in use in The Netherlands. In the first experiment, the colour of veal carcasses was visually assessed by three observers and instrumentally measured with two Minolta CR300 devices.

Residues of veterinary drugs in eggs and their distribution between yolk and white.

Veterinary drugs and feed additives (especially some coccidiostats) can be absorbed by the digestive tract of laying hens and transferred to the egg. Physicochemical characteristics of these compounds determine their pharmacokinetic behavior and distribution to and within the egg. Traditionally the quite lipid soluble drugs and additives are expected to yield residues only in the fat-rich yolk.

Immunity in barren and enriched housed pigs differing in baseline cortisol concentration.

It was shown in a recent study [De Jong IC, Prelle IT, Van de Burgwal JA, Lambooij E, Korte SM, Blokhuis HJ, Koolhaas JM. Effects of environmental enrichment on behavioral responses to novelty, learning and memory and the circadian rhythm in cortisol in growing pigs. Physiol Behav, in press.

Effects of dietary carbohydrates and buffering capacity on nutrient digestibility and manure characteristics in finishing pigs.

A 2 x 3 factorial experiment was conducted with 24 finishing pigs (Yorkshire x [Finnish Landrace x Dutch Landrace]) to determine the effects of dietary buffering capacity (BC) and carbohydrate sources on apparent total tract digestibility (TD), N retention, and manure characteristics. Twelve of these pigs were fitted with steered ileo-cecal value cannulas to measure the apparent ileal digestibility (ID) of N. Experimental variables were two levels of BC (High = 600 mEq/kg and Low = 530 mEq/kg) and three dietary carbohydrates (tapioca [28%], soybean hulls [25%], and sugar beet pulp [25%]).

Antibodies against bovine herpesvirus (BHV) 5 may be differentiated from antibodies against BHV1 in a BHV1 glycoprotein E blocking ELISA.

We examined whether antibodies against bovine herpesvirus (BHV) 5 cross-react with BHV1 antigens and whether they could interfere with BHV1 eradication programmes. Six calves were experimentally infected with different doses of BHV5 strain N569; homologous antibodies were first detectable on day 11 post infection; they cross-reacted in a BHV1 virus neutralisation test, in a BHV1-glycoprotein (g)-B blocking ELISA and in a BHV1-gE ELISA, but not in a BHV1-gE blocking ELISA. This study indicates that, in ongoing BHV1 eradication programmes, based on vaccines that lack gE, BHV5 infections may not lead to false-positive serological reactions in case cattle are tested for BHV1-gE antibodies by the BHV1-gE blocking ELISA; antibodies against BHV5 may be differentiated from antibodies against BHV1.

Behavioural and physiological consequences of acute social defeat in growing gilts: effects of the social environment.

Endocrine, behavioural and immunologic processes, together with body growth, were evaluated in gilts that were defeated at 10 weeks of age in resident-intruder tests. Immediately after defeat, gilts were either separated from or reunited with a familiar conspecific (litter-mate; always a barrow). Gilts were assigned to one of four treatments: (a) DI: defeat, followed by isolation (separation from original litter-mate; n=8); (b) I: no defeat, isolation (control group; n=9); (c) DP; defeat, followed by pair-housing (reunion with original litter-mate; n=8); and (d) P: no defeat, pair-housing (control group; n=8).

Expression of a foreign epitope by porcine reproductive and respiratory syndrome virus.

The potential of porcine reproductive and respiratory syndrome virus (PRRSV) as a viral vector was explored by the insertion of a sequence encoding a foreign antigen into the infectious cDNA clone of the Lelystad virus isolate. An epitope of the hemagglutinin (HA) protein of human influenza A virus was introduced at the 5' end and at the 3' end of ORF7, in each case resulting in a fusion protein between the HA epitope and the nucleocapsid (N) protein. Furthermore, in the construct carrying the HA sequences at the 5' end of ORF7, additional in-frame insertions encoding the autoprotease 2A of foot-and-mouth disease virus were made between the HA and ORF7 sequences to ensure the generation of a functional N protein from its hybrid precursor.

Evolution at the mouse t complex: why is the t haplotype preserved as an integral unit?

Segregation distorters are selfish genetic elements that bias Mendelian segregation in their favor. All well-known segregation distortion systems consist of one or more "distorter" loci that act upon a "responder" locus. At the t complex of the house mouse, segregation distortion is brought about by the harmful effect of t alleles at a number of distorter loci on the wild-type variant of the responder locus.

Genetic parameters of legendre polynomials for first parity lactation curves.

Variance components of the covariance function coefficients in a random regression test-day model were estimated by Legendre polynomials up to a fifth order for first-parity records of Dutch dairy cows using Gibbs sampling. Two Legendre polynomials of equal order were used to model the random part of the lactation curve, one for the genetic component and one for permanent environment. Test-day records from cows registered between 1990 to 1996 and collected by regular milk recording were available.

Fibre area and capillary supply in broiler breast muscle in relation to productivity and ascites.

The objective in this study was to examine the capillary supply in the broiler breast muscle in relation to productivity and the incidence of ascites. Muscle samples (pectoralis superficialis) were collected from 24 pairs of broilers of a commercial paternal strain. The pairs consisted of full sib broilers (brothers and sisters).

Farm animal welfare research in interaction with society.

Over the last 30 years concern about farm animal welfare has increased and has become a public issue in the Netherlands. Public discussion has stimulated research in this field, financed by both government and industry. Dutch society in general and consumers of animal products in particular, want to see high standards of welfare for production animals.

Defence mechanisms against viral infection in poultry: a review.

Defence against viral infections in poultry consists of innate and adaptive mechanisms. The innate defence is mainly formed by natural killer cells, granulocytes, and macrophages and their secreted products, such as nitric oxide and various cytokines. The innate defence is of crucial importance early in viral infections.

Paratuberculosis recognized as a problem at last: a review.

This article attempts to review briefly current opinions on Johne's disease, or paratuberculosis, in ruminants caused by Mycobacterium avium subsp. paratuberculosis. Paratuberculosis has been known to be prevalent in domestic livestock, such as cattle, goats, and sheep, for more than a century.

Diagnosis of bovine spongiform encephalopathy: a review.

Cows affected with bovine spongiform encephalopathy (BSE) display chronic neurological signs consisting of behavioural changes, abnormalities of posture and movement, and/or hyperaesthesia. At present, there are no laboratory test available to diagnose BSE in the live animal. In this article, we describe the post-mortem diagnostic examination of brains from BSE-suspected cattle as currently performed at ID-Lelystad.

Carriers of foot-and-mouth disease virus: a review.

This review describes current knowledge about persistent foot-and-mouth disease virus (FMDV) infections, the available methods to detect carrier animals, the properties of persisting virus, the immunological mechanisms, and the risk of transmission. In particular, knowledge about the carrier state, the period in which virus can be isolated from animals 28 days or longer post infection, is important, because the risk that animals may carry the virus will influence the diagnostic and preventive measures that need to be taken. Although many years of research have led to much knowledge about foot-and mouth disease and its causative agent, there are still numerous aspects of the virus and the disease that are not yet fully understood.

Swine vesicular disease, studies on pathogenesis, diagnosis, and epizootiology: a review.

Swine vesicular disease (SVD) is a contagious viral disease of swine. It causes vesicular lesions indistinguishable from those observed of foot-and-mouth disease. Infection with SVD virus (SVDV) can lead to viraemia within 1 day and can produce clinical signs 2 days after a pig has come into contact with infected pigs or a virus-contaminated environment.

Laboratory diagnosis, epizootiology, and efficacy of marker vaccines in classical swine fever: a review.

Detection of classical swine fever virus (CSFV) can be achieved by a range of assays of which the most commonly used are: immunohistochemical and virus culture techniques. New developments have enabled the detection of viral proteins by enzyme-linked immunosorbent assays (ELISAs) and the detection of the viral genome by RT- PCR. So far, laboratory findings show that the latter assays may supplement or replace the conventional techniques in the near future.

Early accumulation of PrP(Sc) in gut-associated lymphoid and nervous tissues of susceptible sheep from a Romanov flock with natural scrapie.

The immune system is known to be involved in the early phase of scrapie pathogenesis. However, the infection route of naturally occurring scrapie and its spread within the host are not entirely known. In this study, the pathogenesis of scrapie was investigated in sheep of three PrP genotypes, from 2 to 9 months of age, which were born and raised together in a naturally scrapie-affected Romanov flock.

In vitro phagocytosis of boar spermatozoa by neutrophils from peripheral blood of sows.

A considerable number of spermatozoa are used in each sow in routine artificial insemination. However, within a few hours after insemination, many spermatozoa are phagocytosed by polymorphonuclear leucocytes. Some aspects of sperm transport in the female genital tract in the sow have been thoroughly investigated, whereas little is known about the mechanisms involved in the phagocytosis of spermatozoa, or about which spermatozoa (fresh, capacitated or dead) are the most susceptible to ingestion by polymorphonuclear leucocytes.

Presence of bovine herpesvirus 1 gB-seropositive but gE-seronegative Dutch cattle with no apparent virus exposure.

Two hundred and thirty-seven of 2052 cattle which had not been vaccinated against bovine herpesvirus 1 (BHV-1) were seropositive in a glycoprotein B (gB)-blocking ELISA, but seronegative in a glycoprotein E (gE)-blocking ELISA. In order to detect whether they were latently infected with BHV-1, 10 of them were treated with corticosteroids in an attempt to reactivate putatively latent virus. After successive treatments with dexamethasone and prednisolone, no virus excretion was detected and they showed no increase in antibody titres.

The effects of calcium benzoate in diets with or without organic acids on dietary buffering capacity, apparent digestibility, retention of nutrients, and manure characteristics in swine.

Eight barrows (Yorkshire x [Finnish Landrace x Dutch Landrace]), initially 30 kg BW, were fitted with ileal cannulas to evaluate the effects of supplementing Ca benzoate (2.4%) and organic acids (OA) in the amount of 300 mEq acid/kg feed on dietary buffering capacity (BC), apparent digestibility and retention of nutrients, and manure characteristics. Swine were allotted in a 2 x 4 factorial arrangement of treatments according to a cyclic (8 x 5) changeover design.

Genome replication of Newcastle disease virus: involvement of the rule-of-six.

We examined replication of Newcastle disease virus (NDV) by using minigenomes consisting of the 3' leader and 5' trailer regions of NDV flanking a reporter gene encoding secreted placental alkaline phosphatase (SEAP). Negative-sense minigenome RNA was generated from transfected plasmid DNA by means of in vivo transcription. Subsequent replication of minigenome RNA was determined either after infection with NDV helpervirus or after contransfection with helperplasmids that expressed the essential viral replication proteins NP, P, and L.