Establishment and characterization of porcine cytolytic cell lines and clones.

Although non-major-histocompatibility-complex-restricted cytolytic cells appear to significantly influence antiviral immunity in pigs, the phenotype and functional characteristics of these cells are not well defined. To allow a detailed analysis of these subsets, we established and characterized cell lines and clones of interleukin-2-activated (IL-2) cytolytic cells. Cell lines and clones were obtained from peripheral blood mononuclear cells of minipigs of the swine-leucocyte-antigen-complex (SLA) d/d haplotype.

Detection of bovine herpesvirus 1 glycoprotein E antibodies in individual milk samples by enzyme-linked immunosorbent assays.

The purpose of this study was to determine whether individual milk samples can replace serum samples for the detection of bovine herpesvirus 1 (BHV1) glycoprotein E (gE)-specific antibodies. Serum and milk samples were collected at the same time from cattle in BHV1-free herds, cattle in unvaccinated herds, and cattle in herds that were vaccinated twice with a BHV1 marker vaccine. The samples were tested in two gE enzyme-linked immunosorbent assay (ELISA) systems.

Selection for high levamisole resistance in Haemonchus contortus monitored with an egg-hatch assay.

To investigate the characteristics of selection for levamisole resistance in Haemonchus contortus, the consecutive nematode generations of an in vivo selection were monitored with a newly developed egg-hatch assay. The in vivo selection was started with a population not previously exposed to any anthelmintics (SHS). At first, the levamisole resistance progressed gradually in successive nematode generations by treating sheep with increasing doses of levamisole, the initial dose being 1 mg kg-1.

Inactivation of the RNase activity of glycoprotein E(rns) of classical swine fever virus results in a cytopathogenic virus.

Envelope glycoprotein E(rns) of classical swine fever virus (CSFV) has been shown to contain RNase activity and is involved in virus infection. Two short regions of amino acids in the sequence of E(rns) are responsible for RNase activity. In both regions, histidine residues appear to be essential for catalysis.

Muscle fibre type and meat quality.

Muscle morphology and fibre type composition are briefly reviewed in relation to colour stability and tenderness in beef, and water holding capacity, colour and eating quality in pork. A large inter-muscle and inter-animal variation exists in meat quality, which is often related to metabolic and contractile properties as determined by their muscle fibre type distribution. Characteristics of different muscles may be modified in living animals by environmental conditions and genetic selection.

A survey of anthelmintic resistance in nematodes of sheep in The Netherlands.

The prevalence of anthelmintic resistance in nematodes of sheep was surveyed in 1994 on 70 farms in the Netherlands. An in vitro egg hatch assay, faecal egg count reduction (FECR) 14 days after treatment, and larval cultures were used as methods of investigation. Oxfendazole was tested on 69, ivermectin on 51, and levamisole on 36 farms.

A subunit vaccine based on glycoprotein E2 of bovine virus diarrhea virus induces fetal protection in sheep against homologous challenge.

The primary aim of a bovine virus diarrhea virus (BVDV) vaccine is to prevent transplacental transmission of virus. E2 genes of three BVDV strains, belonging to antigenic groups IA, IB and II, were expressed in insect cells. Three groups of 12 ewes were immunized twice with one of the E2 proteins.

Immunization of cattle with a BHV1 vector vaccine or a DNA vaccine both coding for the G protein of BRSV.

A gE-negative bovine herpesvirus 1 (BHV1) vector vaccine carrying a gene coding for the G protein of bovine respiratory syncytial virus (BRSV) (BHV1/BRSV-G) induced the same high degree of protection in calves against BRSV infection and BHV1 infection as a multivalent commercial vaccine. A DNA plasmid vaccine, carrying the same gene as the BHV1/BRSV-G vaccine, significantly reduced BRSV shedding after BRSV infection compared with that in control calves, but less well than the BHV1/BRSV-G vaccine. Flow cytometric analysis showed a significant relative increase of gamma/delta+ T cells in peripheral blood after BRSV challenge-infection of the calves of the control group but not in the vaccinated groups.

Synthetic peptide vaccines: palmitoylation of peptide antigens by a thioester bond increases immunogenicity.

Synthetic peptides have frequently been used to immunize animals. However, peptides less than about 20 to 30 amino acids long are poor immunogens. In general, to increase its immunogenicity, the presentation of the peptide should be improved, and molecular weight needs to be increased.

Biologically safe, non-transmissible pseudorabies virus vector vaccine protects pigs against both Aujeszky's disease and classical swine fever.

Envelope glycoprotein D (gD) of pseudorabies virus (PRV) is essential for penetration but is not required for cell-to-cell spread. When animals are inoculated with a phenotypically complemented PRV gD mutant, the virus is able to spread locally by means of direct cell-to-cell transmission, but progeny virions released by infected cells are non-infectious because they lack gD. Therefore, the virus cannot be transmitted from inoculated animals to other animals.

Inhibition of pestivirus infection in cell culture by envelope proteins E(rns) and E2 of classical swine fever virus: E(rns) and E2 interact with different receptors.

Pure preparations of envelope glycoproteins E(rns) and E2 of classical swine fever virus (CSFV) synthesized in insect cells were used to study infection of porcine and bovine cells with the pestiviruses CSFV and bovine viral diarrhoea virus (BVDV). Almost 100% inhibition of infection of porcine kidney cells with CSFV was produced by 100 microg/ml E(rns). After removal of the virus no E(rns) was needed in the overlay medium (growth medium) to maintain this level of inhibition.

The efficacy of phytase in corn-soybean meal-based diets for laying hens.

Microbial phytase hydrolyzes poorly degradable vegetable phytate P in the gastrointestinal tract of poultry; thereby increasing the availability of organic P to an extent that remains to be established. For this purpose, the P equivalency value of phytase in corn-soybean meal layer diets was assessed in three experiments (two short-term absorption studies and one performance trial lasting a complete production period). In the first absorption study, two basal diets containing 30 or 40 g Ca/kg diet were supplemented with either phytase [0, 250, or 500 phytase units (FTU)/kg diet] or with monocalcium phosphate (MCP; 0, 0.

Fundamentals and recent development in cryopreservation of bull and boar semen.

This paper describes some of the effects of cryopreservation on living sperm, and some recent results for bull and boar semen. During freezing and thawing of semen, the sperm can be damaged by the rapid and dramatic changes in the physicochemical conditions during cooling and ice formation. The rate and extent of these changes, and their impact on the cells, are strongly affected by the cooling rate and the medium composition.

Pathological changes in metabolism of poultry related to increasing production levels.

A continuously increasing production level in poultry breeding has resulted in changes in metabolism. Selection procedures in breeding programmes are focused on an increase in growth rate and on a decrease in feed conversion ratio (less feed intake per unit of deposited tissue). These procedures do not pay attention to the maintenance requirements of birds.

Control of scrapie eventually possible?

After a brief description of the scrapie situation in the Netherlands, the technical progress made in aspects of scrapie diagnosis is reported. Emphasis is placed on the use of immuno-histochemistry (IHC) in the post-mortem histological diagnosis and on the recently published preclinical test for scrapie, in which IHC is applied to tonsillar biopsies. These two approaches use the same IHC technique and enable us to confirm suspected scrapie in individual animals, and for certain genotypes even in the preclinical phase.

Prion protein and scrapie susceptibility.

This article presents briefly current views on the role of prion protein (PrP) in Transmissible Spongiform Encephalopathies or prion diseases and the effect of PrP polymoryhisms on the susceptibility to these diseases, with special emphasis on sheep scrapie. The PrP genotype of sheep appears to be a major risk factor for scrapie, and polymorphisms at codons 136, 154, and 171 modulate the susceptibility of sheep for scrapie. Nevertheless, scrapie is not a spontaneous genetic disease alone.

Effect of resistant starch on net portal-drained viscera flux of glucose, volatile fatty acids, urea, and ammonia in growing pigs.

Net portal-drained viscera (PDV) flux of glucose, VFA, ammonia, and urea was determined in pigs fed diets with or without resistant starch. Diets consisted of 65% cornstarch (diet CS), 32.5% cornstarch and 32.

Effects of trehalose and sucrose, osmolality of the freezing medium, and cooling rate on viability and intactness of bull sperm after freezing and thawing.

The influence of the presence of trehalose or sucrose, the osmolality of the freezing medium, and the cooling rate on success of cryopreservation of bull sperm were investigated. Bull semen was frozen at four different cooling rates varying from 40 to 300 degrees C/min in standard Tris-egg yolk medium and in hypertonic or isotonic media containing 0.2 M trehalose or sucrose.

Microsatellites of the parasitic nematode Haemonchus contortus: polymorphism and linkage with a direct repeat.

To develop tools to analyse parasitic nematode population structures and the effects of selection pressure on the nematode population, we isolated and characterised 13 microsatellite markers of the nematode Haemonchus contortus. The density of CA/GT microsatellites, once in 575 kb, is lower than in mammals. Although the isolated CA/GT repeats were imperfect, the majority of the microsatellites were polymorphic in one or more populations.

The circadian rhythm of salivary cortisol in growing pigs: effects of age, gender, and stress.

This experiment was designed to examine circadian rhythmicity of cortisol in saliva of growing pigs, in relation to age, gender, and (time of) stressor application. Additionally, the acute cortisol response to a stressor was studied. Five groups, each consisting of 3 barrows and 3 gilts, were involved in the experiment.

Plasma catecholamine and corticosterone levels during manual restraint in chicks from a high and low feather pecking line of laying hens.

Neurosympathetic and adrenal responsivity to manual restraint was studied in two White Leghorn chicken lines which differ in their tendency to feather peck. Blood samples were taken from freely moving cannulated birds during resting conditions and during manual restraint (placing the bird on its side for 8 min) to determine plasma noradrenaline. adrenaline and corticosterone.

Glycoprotein Erns of pestiviruses induces apoptosis in lymphocytes of several species.

Classical swine fever virus and bovine virus diarrhea virus are members of the genus pestivirus, which belongs to the family of the Flaviviridae. Recently, envelope glycoprotein Erns was identified as an RNase. RNases can express different biological actions.

Risk of BSE from the import of cattle from the United Kingdom into countries of the European Union.

This study assesses quantitatively the risk that other countries, in particular those within the European Union, have incurred by importing cattle from the United Kingdom during the period before or shortly after the ban on the import of live breeding stock was introduced in 1989. It does this by assessing the probability that animals imported from the UK in a certain year would have become a detected BSE case, had they not been exported. Using the annual incidence rates available for separate birth cohorts and a given culling rate, a cumulative incidence for each birth cohort was calculated.

Causes for variation in pork quality.

Research was carried out on 260 pigs that were slaughtered in 12 batches in the slaughter facilities of ID-DLO at Zeist. The practical circumstances were highly standardized. The 'animals' meat quality was good with only little variation; 46 animals showed a 'slightly' aberrant quality and 6 'slight' DFD.

An enzyme-linked immunosorbent assay to detect antibodies against glycoprotein gE of bovine herpesvirus 1 allows differentiation between infected and vaccinated cattle.

A blocking enzyme-linked immunosorbent assay (ELISA) was developed for detecting antibodies against glycoprotein gE (gE) of bovine herpesvirus 1 (BHV1). The assay is based on the use of two monoclonal antibodies directed against different antigenic domains on gE. Sera from uninfected cattle and cattle that had been repeatedly vaccinated with gE-negative marker vaccines scored negative, whereas sera from cattle naturally or experimentally infected with BHV1 field strains scored positive in the gE-ELISA.