Search

This paper reviews how immunomodulation through active vaccination has evolved in the past 25 years. Although initially it progressed isolated from the main stream of immunological research and vaccine development, lately it merged with this main stream and is taking full advantage of the newest developments in vaccinology. The first immunomodulation vaccine is already on the market, while various others are close to it. Not in the least because one of the major stumbling blocks of immunomodulation through active vaccination, the inherent low immunogenicity of ‘self’ antigens, has in a number of other cases been solved. Most progress has been made in veterinary applications and has helped to formulate practical rules, necessary to break immunotolerance. It is not unlikely that these rules will be used to design better immunomodulation vaccines to be used in humans; notably to control fertility or combat tumours.

Recent devastating outbreaks of foot-and-mouth disease (FMD) in Europe have reopened the discussion about the adequacy of the non-vaccination strategy implemented by the EU in 1991. Here we describe the evaluation of a new commercially available test kit for the discrimination between vaccination and infection. The test is based on the detection of antibodies against the recombinant non-structural (NS) protein 3ABC. In contrast to immunization with vaccines free of 3ABC, these antibodies are elicited as a consequence of infection. Testing more than 3600 negative sera from several countries revealed a specificity of > 99% for bovine, ovine, and porcine samples. Antibodies specific for 3ABC can be detected as soon as 10 days post-infection. As compared with the occurrence of antibodies against structural proteins of FMDV, anti-3ABC antibodies can be detected 5-10 days later, depending on the species. No anti-3ABC antibodies were detected in sera from vaccination experiments or in field sera from vaccinated animals. However, anti-3ABC antibodies can be detected in vaccinated animals upon challenge. These results provide evidence that this test can facilitate the use of vaccines in new strategies against FMD.

Near infrared spectroscopy (NIRS) is one of the most promising techniques for large-scale meat quality evaluation. We investigated the potential of NIRS-based models to predict drip loss and shear force of pork samples. Near infrared reflectance spectra (1000–2500 nm), water-holding capacity, shear force, ultimate pH, and colour (L∗, a∗, b∗-value) of 96 pork longissimus muscles were recorded at 2 days post mortem. Stepwise multiple linear regression (SMLR) and partial least squares regression (PLSR) analyses were used to formulate models for drip loss and shear force. Prediction models for drip loss correlated moderately strong with measured drip loss (R=0.71–0.74), which is similar to the correlation obtained using a combination of ultimate pH, filter paper test, and L∗-value (R=0.74). The current results indicate that NIRS enables the classification of pork longissimus muscles with a superior or inferior water-holding capacity as having a drip loss lower than 5% or higher than 7%. No useful models could be constructed for shear force.

E rns is a pestivirus envelope glycoprotein and is the only known viral surface protein with RNase activity. E rns is a disulfide-linked homodimer of 100 kDa; it is found on the surface of pestivirus-infected cells and is secreted into the medium. In this study, the disulfide arrangement of the nine cysteines present in the mature dimer was established by analysis of the proteolytically cleaved protein. Fragments were obtained after digestion with multiple proteolytic enzymes and subsequently analyzed by liquid chromatography-electrospray ionization mass spectrometry. The analysis demonstrates which cysteine is involved in dimerization and reveals an extremely rare vicinal disulfide bridge of unknown function. With the assistance of the disulfide arrangement, a three-dimensional model was built by homology modeling based on the alignment with members of the Rh/T2/S RNase family. Compared to these other RNase family members, E rns shows an N-terminal truncation, a large insertion of a cystine-rich region, and a C-terminal extension responsible for membrane translocation. The homology to mammalian RNase 6 supports a possible role of E rns in B-cell depletion.

In vivo measurements of the changes over time in rumen degraded and undegraded protein fractions were used to study effects of midwinter shearing of prolific ewes on effective rumen degradability of dietary protein (EPD). Values were compared to EPD estimated with the standard method of in situ feed characteristics and an assumed rumen passage rate. The effect of the experimental treatments (unshorn and shorn) was investigated in ewes during three years (n = 11). Rumens of the sheep were emptied and sampled 1, 2, 4, 8 and 12 h after feeding to monitor rumen contents of dry matter (DM), crude protein-free organic matter (OM-CP) and nitrogen (N). The degraded and undegraded fractions of DM, OM-CP and N in rumen contents were measured by in situ rumen incubation of rumen content samples. Protein evaluation based on EPD estimated from changes in rumen digesta volume with time had more variation and 10% more digestible protein in the small intestine (DVE) than the commonly used EPD. Midwinter shearing of crossbred ewes increased the extent of degradation of DM and OM-CP in the rumen. The extent of degradation of protein tended to be higher in shorn ewes. These differences did not result in different DVE yields with an assumption of an unchanged efficiency of microbial protein growth during cold exposure. While the commonly used EPD is more suitable for routine techniques than EPD based on changes in rumen digesta volume over time, the commonly used EPD may result in an underestimation of the DVE value of feeds for prolific ewes. Protein evaluation should take account of differences in efficiency of microbial production between unshorn and shorn ewes to avoid underestimation of the DVE value of feeds. © 2002 Elsevier Science B.V. All rights reserved.

Large individual differences between adult laying hens in their propensity for feather pecking are known to exist. However, not much research has been carried out into the individual differences concerning the development of feather pecking behaviour. The purpose of this study was to investigate whether contrasting levels of feather pecking, observed among adult birds from two lines of laying hens, already occur at an early age. Further-more, an important question to be discussed was whether different behavioural systems may be related to the occurrence of feather pecking. Therefore, this study consisted of studying and comparing the behaviour of White Leghorn laying hens from a high (HFP) and low feather pecking line (LFP) during the first 8 weeks of life. Chicks were reared in litter-floor pens and were kept in groups of five animals per line (12 groups per line).HFP chicks showed significantly higher levels of gentle feather pecking (gentle FP) than LFP chicks at the age of 14 and 28 days. Furthermore, HFP chicks spent significantly more time preening than LFP chicks on days 14, 28 and 41. Duration of foraging behaviour and feeding behaviour was significantly higher in the LFP line compared to the HFP line on days 41 and 56 and days 28, 41 and 56, respectively. HFP chicks showed a significant negative correlation between gentle FP and preening on days 3 (r = -0.49) and 41 (r = -0.86). In the LFP line duration of feeding correlated negatively with gentle FP on day 3 (r = -0.63). A principal component analysis (PCA) revealed that in the HFP line, gentle FP and preening exhibited high and opposite loadings on the same component at all ages, whereas feeding consistently loaded on the other component. This outcome contrasted with that of the LFP line. In this line feeding predominantly loaded on the same principal component as gentle FP with loadings opposite to those of gentle FP, whereas preening showed the same loadings as gentle FP, on days 3 and 41.In conclusion, differences in feather pecking behaviour between HFP and LFP chicks can already be observed at a very early age during development. Furthermore, our results indicate that HFP and LFP chicks differ in the way pecking behaviour is targeted. This difference could be related to the existence of a difference in underlying motivational system controlling the development of feather pecking between the two lines. (C) 2002 Elsevier Science B.V. All rights reserved.

Homopolymeric nucleotide tracts have been previously identified in the genome sequence of Campylobacter jejuni 11168 [Parkhill et al., Nature 403 (2000) 665-668]. These tracts are believed to regulate contingency genes but as yet no phenotypic variation has been identified associated with many of these genes. To investigate homopolymeric tracts for genes for which there is no observable phenotype, a method was designed to visualise profiles of the various tract lengths directly at the genomic level by means of PCR and denatured polyacrylamide gel electrophoresis. Six of the seven contingency genes investigated displayed variation in the length of the respective homonucleotide tracts. Surprisingly, each contingency gene gave a typical peak profile that represented a conserved size distribution of polymorphic forms. For each gene studied, peak profiles were conserved between strains of C. jejuni. Duplicated genes, containing homonucleotide stretches, displayed locus-specific peak distributions for each gene copy. Contingency genes were polymorphic within single colonies, and the observed complex peak profiles suggested a frequency of slippage several orders of magnitude higher than reported for other organisms. No G7 (or C7) stretch was ever observed, and their absence from the complete genome suggests strong selection against their presence. In view of the predictable outcome of the process leading to these polymorphisms, it is hypothesised that the formation and/or selection of these tracts is not a random process, but is driven by as yet unknown mechanism(s). High-frequency polymorphism of these genes may be a mechanism by which C. jejuni survives selection bottlenecks between opportunities for growth within a host.

Gastroenteritis caused by Campylobacter spp. infection has been recognized as one of the important public health problems in the developed countries. Outbreaks mostly originate from the consumption of contaminated poultry or infected water. The aim of this study was to determine the bactericidal activity on Campylobacter spp. of organic acids individually and in combinations at different pH levels and times and to compare bactericidal activities with activities of commercially available products. Ten strains of Campylobacter spp. were added in a mixture of water with commercial broiler feed, separately adjusted by four acids: formic, acetic, propionic, and hydrochloric acids, into pH 4.0, 4.5, 5.0, and 5.5. A combination of three organic acids was used in two different formulation ratios: formic:acetic:propionic at 1:2:3 and 1:2:5, at pH 4.0, 4.5, 5.0, and 5.5. All organic acids showed the strongest bactericidal effect on Campylobacter at pH 4.0. In contrast, at pH 5.0 and 5.5, the bactericidal activity of the four acids was low. The combination of organic acids showed a synergistic bactericidal activity at pH 4.5. Interestingly, the effect of the combined organic acids was stronger than the commercial products. Morphological cell changes were studied by transmission electron microscopy to determine the effect of the organic acids on the cell structure of Campylobacter. Some loss of outer membranes of the bacteria could be found in treated groups. Therefore, it can be concluded that organic acids, individually or in combination, have a strong bactericidal effect on Campylobacter spp. Routine application of organic acids to the water supply on poultry farms could prevent or diminish Campylobacter transmission.

Advantages of laparoscopic surgery have, among other factors, been attributed to a shorter length of abdominal incision and the use of CO2 versus air. An analysis of these factors taking pressure-induced alterations into account is lacking. The objective of the study was to determine the impact of laparoscopy and laparotomy with exposure to CO2 and room air under a similar pressure on local, systemic, and distant organ immune responses. Twenty piglets were randomized into four groups: CO2 laparoscopy, air laparoscopy, CO2 laparotomy, and air laparotomy. Laparotomy was performed in a sterile balloon pressurized similar to laparoscopy. Peritoneal interleukin-1, interleukin-6, tumor necrosis factor-α, and counts of polymorphnuclear cells (PMNs), and macrophages (MFs) were determined in abdominal lavage fluids at 0, 2, and 48 h. Macrophages were assessed for reactive oxygen species (ROS) production. Systemic responses were gauged by white blood cell count (WBC) and cytokines. Alveolar lavage was performed at 48 h to determine cytokine levels, cell counts, and MF ROS production. Blood, lavage fluids, and mesenteric lymph nodes were tested for bacterial translocation. Regarding the peritoneal response, laparotomy versus laparoscopy when performed with CO2 significantly increased PMN and decreased the percentage of macrophages (%MF) up to 48 h. There was a significant increase in interleukin-6, and there was a fourfold increase in MF ROS production. Similar differences between the procedures were found with exposure to air. The use of air versus CO2 in laparoscopy, but not in laparotomy, resulted in an increase of peritoneal PMN and a decrease of the %MF up to 48 h. Air increased the local interleukin-6 release in both procedures and increased MF ROS production fourfold. Regarding the systemic response, laparotomy produced a significant increase in WBC, which was significantly more pronounced with exposure to air. No alteration of other systemic cytokines was seen. Regarding the pulmonary response, the number of MFs and MF ROS production were significantly increased after air versus CO2 laparoscopy. There were no such differences between the laparotomy groups. Regarding bacterial translocation, no bacteria were cultured from peritoneal fluids, lymphnodes, or blood. Inflammatory responses were reduced by a laparoscopic approach and by exposure to CO2 versus air. Peritoneal responses were affected to a larger degree than systemic parameters. Laparotomy overruled the effects of CO2 on chemotaxis and distant organ injury but not on peritoneal cytokine release.

In this study, we examined whether an experimental bovine herpesvirus 4 (BHV4) infection can induce bovine mastitis, or can enhance bovine mastitis induced by Streptococcus uberis (S. uberis). Four lactating cows were inoculated intramammarily and intranasally with BHV4, and four lactating control cows were mock-inoculated. After 14 days, two of four cows from each group were inoculated intramammarily with S. uberis. No clinical signs were recorded in cows inoculated only with BHV4, and their milk samples showed no abnormal morphology, despite the fact that BHV4 replicated in inoculated quarters. Somatic cell count increased significantly in milk from three of six BHV4-inoculated quarters, compared to the non-inoculated quarters of the same cows (within-cow) and the quarters of mock-inoculated cows (control group) on days 8, 9 and 11 post-inoculation (pi). BHV4 was isolated from nasal swabs between days 2 and 9 pi. Clinical mastitis was observed in all four cows intramammarily inoculated with S. uberis. A preceding BHV4 infection did not exacerbate the clinical mastitis induced by S. uberis. S. uberis infections appeared to trigger BHV4 replication. From one quarter of each of two cows inoculated with BHV4 and S. uberis, BHV4 was isolated, and not from quarters inoculated with BHV4 only. In conclusion, BHV4 did not induce bovine clinical mastitis after simultaneous intranasal and intramammary inoculation. However, the BHV4 infection did induce subclinical mastitis in 50% of the cows and the quarters.

Two experiments of similar design were conducted with male broiler chickens over two body weight ranges, 200 to 800 g in Experiment 1 and 800 to 1,600 g in Experiment 2. The data were used to test the hypothesis that protein deposition rate increases (linearly) with increasing amino acid intake, until energy intake becomes limiting for protein deposition rate. Additional amino acid intake above this point would be deposited less efficiently. An increase in energy intake would increase lipid deposition rate, but should, at low amino acid intakes, not affect protein deposition rate. Each experiment consisted of 18 treatments: two levels of protein-free energy (energy(pf)) intake, combined with nine amino acid to energypf ratios. Protein was balanced for amino acid content and lysine was the first limiting amino acid in the diet. Protein deposition rate increased with additional amino acid intake. No evidence was found that energy(pf) intake limited protein deposition rate at high amino acid intake. Extra intake of energy(pf) increased lipid deposition rate, which was independent of amino acid intake. Where amino acid intake was limiting, additional intake of energy(pf) had generally no effect on protein deposition rate. The marginal efficiency of amino acid utilization for protein deposition did not depend on body weight. The facts are relevant to the modeling of the growth of broiler chickens.

The performance of clinical signs as a diagnostic test for the detection of classical swine fever (CSF) outbreaks during the 1997–1998 CSF epidemic in The Netherlands was evaluated by constructing and analysing a receiver operating characteristic (ROC) curve. This curve assesses the discriminating ability of a diagnostic test over a range of test signals. The cut-off values for a defined diagnostic test to detect CSF outbreaks were set by different combinations of clinical signs observed. The area under the ROC curve, which is a quantitative measure of test performance, was significantly (P

Organic matter (OM) degradation of 21 feedstuffs was investigated with rumen fluid using a rumen in situ technique and a gas production technique. Fitting the nylon bag data to an exponential model showed that there was a high variation in the rate of OM degradation ranging from 1.7% h-1 for protected solvent extracted soybean meal to 10.5% h-1 for potato pulp. The percentage fermentable OM (FOM), calculated from the nylon bag data, ranged from 26.9% for maize gluten meal to 76.4% for pea meal. Gas production was recorded with fully automated equipment using twice-diluted rumen fluid. The gas production profiles were fitted to a mono-phasic and a tri-phasic model. The aim of the study described is to investigate the possibilities to estimate in situ degradation characteristics using gas production characteristics and chemical composition. The in situ washout fraction (W), degradable fraction (D) and undegradable fraction (U) could be predicted from chemical composition and gas production parameters with R2 ranging from 0.50 to 0.72. There was a closer relationship between in situ degradation rate of OM (kd) and the incubation period halfway to maximum gas production (B), using the tri-phasic model (R2 = 0.58) than the mono-phasic model (R2 = 0.43). Accounting for an in situ lag-period slightly improved prediction of kd by gas production parameters (R2 = 0.47-0.62). Percentage FOM, calculated from in situ results, could be predicted from chemical composition and gas production parameters with R2 ranging from 0.50 to 0.75. Transformation of kd (determined in situ) to its half-life value of degradation ((ln 2/kd) × 100) provided a slight improvement of kd prediction by chemical composition and gas production parameters, with R2 ranging from 0.56 to 0.81. There was only a moderate relationship for OM degradation in these feedstuffs determined using an in situ and a gas production technique. © 2002 Elsevier Science B.V. All rights reserved.

International audience; Genetic resistance to diseases is a multigenic trait governed mainly by the immune system and its interactions with many physiologic and environmental factors. In the adaptive immunity, T cell and B cell responses, the specific recognition of antigens and interactions between antigen presenting cells, T cells and B cells are crucial. It occurs through a network of mediator proteins such as the molecules of the major histocompatibility complex (MHC), T cell receptors, immunoglobulins and secreted proteins such as the cytokines and antibodies. The diversity of these proteins that mainly is due to an intrinsic polymorphism of the genes causes phenotypic variation in disease resistance. The well-known linkage of MHC polymorphism and Marek's disease resistance difference represents a classic model revealing immunological factors in resistance differences and diversity of mediator molecules. The molecular bases in any resistance variation to infectious pathogens are vaguely understood. This paper presents a review of the major immune mediators involved in resistance and susceptibility to infectious diseases and their functional mechanisms in the chicken. The genetic interaction of disease resistance with production traits and the environment is mentioned.; Bases immunologiques des différences dans la résistance aux maladies chez le poulet. La résistance génétique aux maladies est un trait multigénique qui est surtout gouverné par le système immunitaire et ses interactions avec de nombreux facteurs physiologiques et environnementaux. Dans l'immunité acquise, les réponses des cellules T et B, la reconnaissance spécifique des antigènes et les interactions entre les cellules présentant des antigènes, les cellules T et B, sont cruciales. Cela se produit à travers un réseau de protéines médiatrices telles que les molécules du complexe majeur d'histocompatibilité (CMH), les récepteurs des cellules T, les immunoglobulines et les protéines sécrétées telles que les cytokines et les anticorps. La diversité de ces protéines, qui est surtout due au polymorphisme intrinsèque des gènes, entraîne une variation phénotypique dans la résistance aux maladies. Le lien bien connu entre le polymorphisme du CMH et les différences dans la résistance à la maladie de Marek représente un modèle classique révélant les facteurs immunologiques dans les différences de résistance et la diversité dans les molécules médiatrices. Les bases moléculaires impliquées dans toute variation de résistance aux pathogènes infectieux sont à peu près comprises. Cet article présente une synthèse sur les principaux médiateurs de l'immunité impliqués dans la résistance et la sensibilité aux maladies infectieuses chez le poulet et leurs mécanismes fonctionnels. L'interaction génétique entre la résistance aux maladies et les traits de production et l'environnement est mentionnée.

In the present study we investigated the role of the fibronectin (FN)- and fibrinogen (FGN)-binding protein (FBPS) in the pathogenesis of Streptococcus suis serotype 2 in piglets. The complete gene encoding FBPS from S. suis serotype 2 was cloned in Escherichia coli and sequenced. The occurrence of the gene in various serotypes was analyzed by hybridization studies. The FBPS protein was expressed in E. coli and purified, and binding to human FN and FGN was demonstrated. The induction of antibodies in piglets was studied upon infection. An isogenic mutant unable to produce FBPS was constructed, and the levels of virulence of the wild-type and mutant strains were compared in a competitive infection model in young piglets. Organ cultures showed that FBPS was not required for colonization of the tonsils but that FBPS played a role in the colonization of the specific organs involved in an S. suis infection. Therefore, the FBPS mutant was considered as an attenuated mutant.

The pestivirus envelope glycoprotein E(rns) has RNase activity and therefore was suspected to enter cells to cleave RNA. The protein contains an RNase domain with a C-terminal extension, which shows homology with a membrane-active peptide. The modular architecture and the C-terminal homology suggested that the C terminus could be responsible for the presumed translocation. Peptides corresponding to the C-terminal domain of E(rns) and also the homologous L3 loop of ribotoxin II were indeed able to translocate across the eukaryotic cell membrane and were targeted to the nucleoli. The entire E(rns) protein was also able to translocate into the cell. Furthermore, other labeled proteins and even active enzymes could be transported inside the cell when they were attached to the C-terminal E(rns) peptide. Translocation was energy-independent and not mediated by a protein receptor. The peptides showed no specificity for cell type or species.

Apparently healthy Rousettus aegyptiacus bats were randomly chosen from a Dutch colony naturally infected with European bat lyssavirus subgenotype 1a (EBL1a). These bats were euthanised three months after the first evidence of an EBL1a infection in the colony. EBL1a genomic and antigenomic RNAs of the nucleoprotein gene were detected by nested reverse transcriptase PCR in 75% of the examined Rousettus aegyptiacus bats. The EBL1a RNAs of the nucleo-protein gene were detected mainly in brain tissues, but also in other organs. EBL1a messenger RNAs of the nucleoprotein gene and the glycoprotein gene were detected in brain tissues. The standard fluorescent antibody test revealed the presence of lyssavirus antigens in brain tissues from 7 (17.5%) Rousettus aegyptiacus bats. Furthermore, EBL1a could not be detected by virus isolation on murine neuro-blastoma cells or by intracerebral inoculation of suckling mice. Neutralising antibodies directed against EBL1 were detected in 11% of the examined bats. This study shows that at least 85% of the apparently healthy Rousettus aegyptiacus bats must have been infected with EBL1a, and that these bats may survive from an EBL1a infection. Furthermore, the study supports the possibility of a long-term maintenance of EBL1a genome in Rousettus aegyptiacus bats.

A novel and robust method for the fine-scale mapping of genes affecting complex traits, which combines linkage and linkage-disequilibrium information, is proposed. Linkage information refers to recombinations within the marker-genotyped generations and linkage disequilibrium to historical recombinations before genotyping started. The identity-by-descent (IBD) probabilities at the quantitative trait locus (QTL) between first generation haplotypes were obtained from the similarity of the marker alleles surrounding the QTL, whereas IBD probabilities at the QTL between later generation haplotypes were obtained by using the markers to trace the inheritance of the QTL. The variance explained by the QTL is estimated by residual maximum likelihood using the correlation structure defined by the IBD probabilities. Unlinked background genes were accounted for by fitting a polygenic variance component. The method was used to fine map a QTL for twinning rate in cattle, previously mapped on chromosome 5 by linkage analysis. The data consisted of large half-sib families, but the method could also handle more complex pedigrees. The likelihood of the putative QTL was very small along most of the chromosome, except for a sharp likelihood peak in the ninth marker bracket, which positioned the QTL within a region

The effect of extra vitamin E (2025 International Units animal–1 day–1) in the diet of bulls on the colour stability and lipid oxidation of lean mince was studied. Control and enriched diets were provided for the last 136 days before slaughter. Minces were prepared from M. biceps femoris and M. semitendinosus that had been stored for 2 months at –40 °C. Samples of minces with and without an ascorbic acid preparation (AAP) from control (CON) and supplemented (SUP) beef were packaged, half on trays over-wrapped with an oxygen-permeable foil and half in modified atmosphere (MA) packs (gas mixture applied: O2/CO2/N2, 75/20/5). Meats were displayed for 7days at 7 °C in an illuminated environment. The SUP meat was more resistant to lipid oxidation than the CON meat was. Also, the AAP consistently delayed lipid oxidation. A strong synergistic effect of both vitamins in this regard was demonstrated for the MA condition. MA packaging overall led to increased lipid oxidation. Colour measurements of SUP versus CON meats, without the AAP, generally failed to detect differences in redness values. The positive effect on the colour of freshly minced lean meats obtained by supplementation with vitamin E appeared to be almost nullified in minces made from previously stored frozen muscles. A sensory panel, however, still tended to judge the attractiveness of the colour of the SUP meat greater than that of CON meat. Addition of the AAP improved colour stability. Compared to the foil-overwrapped meat, colour was better retained in the MA packaged meat.

Various random regression models have been advocated for the fitting of covariance structures. It was suggested that a spline model would fit better to weight data than a random regression model that utilizes orthogonal polynomials. The objective of this study was to investigate which kind of random regression model fits best to weight data of pigs. Two random regression models that described weight of individual pigs, one using orthogonal polynomials, and the other using splines, were compared. A comparison with a multivariate model, Akaike's information criterion, and the Bayesian-Schwarz information criterion were used to select the best model. Genetic, permanent environmental, and total variances increased with age. Heritabilities for the multivariate model ranged from 0.14 to 0.19, and for both random regression models the heritabilities were fluctuating around 0.17. Both genetic and phenotypic correlations decreased when the interval between measurements increased. The spline model needed fewer parameters than the multivariate and polynomial models. Akaike's information criterion was least for the spline model and greatest for the multivariate model. The Bayesian-Schwarz information criterion was least for the polynomial model and greatest for the multivariate model. Residuals of all models were normally distributed. Based on these results, it is concluded that random regression models provide the best fit to pig weight data.

Three mutants with deletions in the E2 gene of the infectious DNA copy of the classical swine fever virus (CSFV) strain-C were constructed: one missing the B/C domain of CSFV-E2 between amino acids (aa) 693 and 746, one missing the A domain between aa 800 and 864, and one missing the complete E2 between aa 689 and 1062. All three CSFV-E2 deletion mutants were unable to generate viable virus, indicating that each of the antigenic domains of E2 is essential for viability of CSFV. To rescue the CSFV-E2 deletion mutants SK6 cell lines constitutively expressing glycoprotein E2 of CSFV were generated. The rescued viruses infected and replicated in SK6 cells as demonstrated by expression of viral proteins, but this primary infection did not result in reproduction of infectious virus. Thus, these E2 complemented viruses are considered non-transmissible. In previous experiments, we showed that simultaneous injection of E(rns) complemented virus (Flc23) via intradermal (ID), intramuscular (IM) or intranasal (IN) routes conferred protection to pigs against a lethal challenge with CSFV [J. Virol. 74 (2000) 2973]. Here, we evaluate different routes of application (ID, IM or IN) with E(rns) complemented virus Flc23 in order to find the best route for complemented CSFVs. Intradermal injection with Flc23 protected pigs against a lethal CSFV challenge, whereas intramuscular injection induced partial protection, and intranasal injection did not mediate a protective immune response in pigs at all. We used the intradermal route of vaccination to test the E2 complemented viruses. Vaccination of pigs via the intradermal route with the E2 complemented CSFVs also resulted in the induction of antibodies and in (partial) protection against CSFV challenge. Pigs vaccinated with E2 complemented virus Flc4 (deletion B/C domain) survived a lethal CSFV challenge, whereas partial protection was induced in pigs vaccinated with Flc47 (deletion E2) or Flc48 (deletion A domain) E2 complemented viruses. Serological data demonstrate that these E2 complemented mutant viruses are, in combination with well known diagnostic tests based on E2, potential marker vaccines for CSF.

Phosphorus (P) balance, and blood plasma P and saliva P concentrations were measured in multiparous dairy cows through two lactations and two dry periods. The cows were fed three amounts of P at either 100, 80 or 67% of the Dutch P recommendation, actually resulting in dietary P concentrations of 3.2 to 3.9, 2.6 to 2.9 and 2.2 to 2.6 g P/kg dry matter during lactation for the three treatments, respectively. On the basis of plasma P values as low as 0.9 mmol/l and saliva P values as low as 5.1 mmol/l during the second lactation period within the experiment, the 67% group was considered to be deficient in P. By decreasing milk production, and thus lowering P losses with milk, P retention in the 67% group remained near zero. The P supply with the 80% ration was considered to be just sufficient. At high milk yield and marginal dietary P concentrations, plasma P and saliva P concentrations were decreased. The higher P intake in high-compared with low-producing cows resulted in a constant absolute fecal P excretion, due to the fact that the apparent P digestibility was raised with increasing milk yield. There was a direct relationship between milk P output and the percentage of apparent P digestibility for individual animals.

Recently, due to consumers fears concerning BSE and vCJD, the need arose for methods to detect BSE, to estimate the present prevalence of BSE among cattle and to predict future BSE prevalence. As a part of that set of urgent questions, it has become important to indicate groups in which BSE risk is higher or lower. One of the well-known risk factors for BSE is age: very young animals do not develop the disease, and very old animals are less likely to develop the disease. Using age-structured modelling, three factors influencing the age distribution of BSE were found to be important: (1) the incubation period of BSE, (2) age structure of the cattle population, and (3) the local risk history (methods of rendering, feeding of compound feed containing Meat and Bone Meal (MBM), and the development of BSE control). The EU has considered these three risk factors to be the most important for BSE risk assessment. So far, this EU risk assessment method has been proven right by several countries detecting BSE after being classified as ‘BSE is most likely present here’. The age distribution of BSE seems to vary a lot between countries and regions. When information on these three factors is available, the expected age distribution of BSE in different countries can be calculated. Our calculations show that in countries where, until very recently, the reproduction ratio was high, (i.e., BSE risk factors were high), the BSE prevalence is expected to be highest in 4-year-old cattle. In countries with low reproduction ratio for BSE, (i.e., BSE control at a very high level) for more than 5 years, the prevalence will be highest in the 6–8-year-old cattle. Thus, surveillance could be targeted specifically at the age groups with the highest BSE risk. For each country, a short assessment shows in which age group BSE is most likely to be found.

Leptin is a 16-kDa protein synthesized by adipose tissue and is involved in regulation of feed intake, energy balance, fertility, and immune functions. Since evidence of a genetic correlation between start of luteal activity and energy balance, milk yield, and live weights is present, we investigated the association of genetic differences in the bovine leptin gene with these traits. Between 1990 and 1997, a total of 613 Holstein-Friesian heifers of two genetic groups with known pedigree were followed from parturition until d 105 of lactation. During the first 15 wk of lactation live weight, feed intake, and milk yield were measured for 565 cows. The start of luteal activity was set at the first day with a progesterone concentration higher than 3 ng/ml. In addition to the interval between calving and start of luteal activity, analyses were performed for average milk yield, percentage fat, protein, and lactose in milk, dry matter intake, feed intake, energy balance, and live weight over the first 15 wk of lactation. All 613 cows were genotyped for two restricted fragment length polymorphisms and for the BM1500 microsatellite, all located at the leptin gene locus. Significances of the genotype effects were estimated using the approximated F-statistic provided by ASREML. Fixed effects were year-season, genetic group, and a quadratic polynomial for age at calving. Animal was fitted as a random effect including the additive relationship between animals to account for background genes. Firstly, each genotype effect was fitted in turn, and secondly the other restriction fragment length polymorphisms were fitted as a cofactor to take into account effects of linkage disequilibrium. Thirdly, sire x genotype interaction was investigated. Heifers with the RFLP1-AB genotype produce 1.32 kg/d more milk and consume 0.73 kg/d more food compared with the RFLP1-AA genotype. No effects were found for start of luteal activity. When linkage disequilibrium with the other markers was taken into account and DMI was included as fixed effect in the model a 0.96 kg/d higher milk yield was still found. Assuming that no pleiotropic effects on traits such as immunity and milk production in later lactations exist, future breeding programs favoring the RFLP1 B-allele can yield a higher milk production without negatively affecting energy balance and fertility. The prospects are good because in this study the frequency of the RFLP1 AB- and BB-genotypes were only 18.5 and 0.2%, respectively.

We study the statistical inference from data on transmission obtained from one-to-one experiments, and compare two algorithms by which the reproduction ratio can be quantified. The first algorithm, the transient state (TS) algorithm, takes the time course of the epidemic into account. The second algorithm, the final size (FS) algorithm, does not take time into account but is based on the assumption that the epidemic process has ended before the experiment is stopped. The FS algorithm is a limiting case of the TS algorithm for the situation where time tends to infinity. So far quantification of transmission has relied almost exclusively on the FS algorithm, even if the TS algorithm would have been more appropriate. Its practical use, however, is limited to experiments with only a few animals. Here, we quantify the error made when the FS algorithm is applied to data of one-to-one experiments not having reached the final size. We conclude that given the chosen tests, the FS algorithm underestimates the reproduction ratio R0, is liberal when testing H0[ratio]R0[gt-or-equal, slanted]1 against H1[ratio]R01 and calculates the same probability as the TS algorithm when testing H0[ratio]R0-control = R0-treatment against H1[ratio]R0-control>R0-treatment. We show how the power of the test depends on the duration of the experiments and on the number of replicates. The methods are illustrated by an application to porcine reproductive and respiratory syndrome virus (PRRSV).

After a short introduction on Porcine Reproductive and Respiratory Syndrome (PRRS) regarding the history, the first occurrence in several countries, and the causal virus, designated Lelystad virus, a description is given of the clinical aspects and several diagnostic methods. After some general remarks on the clinical aspects, the epidemic and the endemic phase of the disease are described. Regarding the diagnosis, special attention is paid to the detection of antibodies and of the PRRS Virus (PRRSV). Regarding the detection of antibodies, a description is given of three tests: the immunoperoxidase monolayer assay, the enzyme-linked immunosorbent assay, and the serum neutralization test. Concerning the detection of PRRSV, attention is paid to the isolation of the virus, the demonstration of PRRSV antigens in frozen or fixed tissue using immunohistochemistry or immunofluorescence, the in situ hybridisation technique and the Polymerase Chain Reaction (PCR).

The large offspring syndrome (LOS) is observed in bovine and ovine offspring following transfer of in vitro-produced (IVP) or cloned embryos and is characterized by a multitude of pathologic changes, of which extended gestation length and increased birthweight are predominant features. In the present study, we used bovine blastocysts to analyze cellular parameters, i.e., the number of cells in Day 7 blastocysts and the size of Day 12 elongating blastocysts, and molecular parameters, i.e., the relative abundance of developmentally important genes: glucose transporter (Glut) 1, Glut-2, Glut-3, Glut-4, heat shock protein (Hsp) 70.1, Cu/Zn-superoxide dismutase (SOD), histone H4.1, basic fibroblast growth factor (bFGF), insulin-like growth factor (IGF) I receptor (R), and IGFII-R. Some blastocysts were produced by in vitro maturation and fertilization followed by in vitro culture in synthetic oviduct fluid medium supplemented with BSA or human serum or by in vivo culture in the sheep oviduct. Other blastocysts were derived in vivo from the uterine horns of superovulated donors. The findings made in the early embryos were related to a representative number of calves obtained from each production system and from artificial insemination (AI). In vitro culture of bovine embryos in the presence of high concentrations of serum or BSA significantly increased the number of cells in Day 7 blastocysts, the size of blastocysts on Day 12, and the relative abundance of the transcripts for Hsp70.1, Cu/Zn-SOD, Glut-3, Glut-4, bFGF, and IGFI-R when compared with embryos from the in vivo production groups. Birthweights of calves derived from IVP embryos were significantly higher than those of calves derived from sheep oviduct culture, superovulation, or AI. The results support the hypothesis that persistence of early deviations in development is causally involved in the incidence of LOS, in particular in increased birthweights. The cellular and molecular parameters analyzed in this study can be considered early markers of LOS in cattle.

Visiontechnieken zijn de meest recente apparatuur om varkenskarakassen te classificeren en volledig automatisch te beoordelen

An experiment was performed in primiparous dairy cows (n = 23) to examine consistency of individual differences in reactivity to milking, and correlations between measures of behavior, physiology, and milk ejection. Responsiveness to milking was monitored during the first machine milking, on d 2 of lactation, and during milkings on d 4 and 130 of lactation. Measurements included kicking and stepping behavior, plasma cortisol and plasma oxytocin, heart rate, milk yield, milking time, milk flow rate, and residual milk obtained after administration of exogenous oxytocin. With repeated early lactation milkings, residual milk and the incidence of abnormal milk flow curves decreased. On d 130 of lactation all heifers exhibited normal milk ejection. Except for higher plasma cortisol concentrations on d 2, all measures were consistent over time between d 2 and 4 of lactation as indicated by significant rank correlations. Individual differences in the behavioral response to udder preparation were consistent over time between early lactation milkings and d 130 of lactation. Residual milk, milk yield, maximum milk flow rate, plasma oxytocin and heart rate during udder preparation were similarly interrelated on d 2 and 4 of lactation. High heart rate responses on d 2 and 4 were associated with enhanced inhibition of milk ejection. In contrast, behavior recorded during the milking process was unrelated to ease of milk removal. Our results indicate that milking at the beginning of lactation may be stressful to some heifers, to the extent that milk ejection is inhibited, but less disturbing to others. The existence of consistent behavioral and physiological responses in the present study suggests that responsiveness of dairy heifers to milking is mediated by stable animal characteristics.

Retinal microglia originate from hemopoietic cells and invade the retina from the retinal margin and the optic disc, most likely via the blood vessels of the ciliary body and iris, and the retinal vasculature, respectively. The microglial precursors that appear in the retina prior to vascularization are major histocompatibility complex (MHC) class I- and II-positive and express the CD45 marker, but lack specific macrophage markers. They differentiate into ramified parenchymal microglia in the adult retina. A second category of microglial precursors, which do express specific macrophage markers, migrate into the retina along with vascular precursors. They appear around blood vessels in the adult retina and are similar to macrophages or cells of the mononuclear phagocyte series (MPS). Microglia are distributed in the outer plexiform layer (OPL), outer nuclear layer (ONL), inner plexiform layer (IPL), ganglion cell layer (GCL), and nerve fiber layer (NFL) of the primate retina. The pattern of microglial distribution in the avascular retina of the quail indicates that blood vessels are not responsible for the final location of microglia in the retina. In the human retina, microglia express MHC class I, MHC class II, CD45, CD68, and S22 markers. In the rat and mouse retina, OX41, OX42, OX3, OX6, OX18, ED1, Mac-1, F4/80, 5D4 anti-keratan sulfate, and lectins are used to recognize microglia. Microglial cells play an important role in host defense against invading microorganisms, immunoregulation, and tissue repair. During neurodegeneration, activated microglial cells participate in the phagocytosis of debris and facilitate regenerative processes. In autoimmune disease, microglia have dual functions: initiating uveoretinitis, but also limiting subsequent inflammation. Retinal microglia may be associated with vitreoretinopathy, diabetic retinopathy, glaucoma, and age-related macular degeneration. The goal of this article was to review the present knowledge about retinal microglia and the function of retinal microglia in pathological conditions.

In 1999, among 164 randomly selected Dutch sheep farmers, a questionnaire was carried out to estimate the prevalence of myiasis in sheep and to investigate factors associated with the occurrence of myiasis. The total number of sheep and/or lambs on the reference date 1 August 1999 was 12,200: 5243 ewes, 225 rams, 3393 ewe- and 3339 ram lambs. On 86 (52.4%) of the farms 349 (2.9%) of all sheep and/or lambs contracted myiasis, of which two died. Myiasis was seen significantly more frequently on farms with over 25 ewes compared to smaller farms. Cases of myiasis were detected from April to September, with a peak (47.1%) in August. Occurrence of myiasis was most frequently associated with hot and humid weather and was mainly observed (69.1%) in the area around the tail.Ewes and ewe lambs had significantly more myiasis when compared with rams and ram lambs. There was no relationship with tail docking, with breed, with the time of shearing, with the kind of soil (clay, sand, etc.), with the environment (bush, trees, water, etc.), with the type of treatment (pour on, dipping, spraying), the used insecticides (synthetic pyrethroïds, diazinon, cyromazin, etc.), the number of preventive treatments, the time of treatment or the number of observations on the herd (once a day, once a week, etc.).

It was observed that farmed eels could be rendered unconscious and insensible instantaneously by passing an electrical current through fresh water. The general epileptiform insult on the EEG was characterized by a tonic/clonic and an exhaustion phase. After stunning, the ECG (electro-cardiogram) revealed fibrillation. The electrical stunning parameters were on average 194 ± 4 V and 0.636 ± 0.040 A/dm2 for 1.6 ± 0.4 s. Within a confidence level of 95L taking into account the number of animals with a reliable EEG (n = 29), at least 93 f all eels are effectively stunned in fresh water by an average current of 0.636 ± 0.040 A/dm2. The behaviour of groups of five eels, which were able to move freely in the water was observed before and after stunning with 50 V and 0.17 A/dm2. After 3-s stunning, two eels were turned upside down. They changed to a normal position after 10 and 13 s respectively. Subsequently, all eels were very active in swimming behaviour and stopped swimming after 75 s. When stunned for a longer duration, all eels were turned upside down and stopped breathing for a limited period of time. In the last experiment the eels were stunned in fresh water (500 ?S) with a voltage of 200 V for approximately 1 s, which was followed by 50 V for 5 min. As soon as the stunning started the water was de-oxygenated by flushing nitrogen to kill the eels by suffocation during the period of unconsciousness and insensitivity. The oxygen saturation decreased from 74 ± 10 to 23 ± 11 t 22 °C. After stunning no brain activity and no responses to pain stimuli were observed on the EEG. The heart rate increased (P < 0.05) after stunning, which was followed by a significant decrease. Only 1 out of 18 eels returned partially from upside down to a normal position 2 h after stunning; however, the eel did not respond to pain stimuli in behaviour. The developed stunning procedure can be recommended for humane slaughter of 50-kg batches of eels.

The problem of how to objectively assess the overall welfare status of animals under farming conditions has contributed to an ongoing debate that has hampered actual decision making on animal welfare. For this reason we constructed a model based on the assumed hierarchical organization of the animals’ needs for overall welfare assessment in the case of pregnant sows. This model is implemented in a computer-based decision support system that takes a description of a housing and management system as input and produces a welfare score as output. A formalized procedure was used to construct the model for welfare assessment in pregnant sows on the basis of available scientific knowledge. This SOWEL (from SOw WELfare) model contains 37 attributes that describe the welfare-relevant properties of housing and management systems. In the decision support system these attributes are linked to scientific statements and a list of needs to provide a scientific basis for welfare assessment. Weighting factors that represent the relative importance of the attributes are derived from the scientific statements about the various welfare performance criteria that have been measured by scientists. The welfare score is calculated as the weighted average score. All information in the decision support system is stored in tables in a relational database such that newly available knowledge and insights can be incorporated to refine the model. The model has been developed in line with several existing models but it differs from these models in that it is the first to provide a formalized procedure to explicate the reasoning steps involved in welfare assessment based on available scientific knowledge.

Molecular epidemiology studies suggest that horizontal genetic exchange is a major cause of pathogen biodiversity. We tested this concept for the bacterial enteropathogen Campylobacter jejuni by seeking direct in vivo evidence for the exchange of genetic material among Campylobacter strains. For this purpose, two antibiotic resistance markers were inserted into the hipO or htrA gene of genetically distinct and naturally transformable C. jejuni strains. Genetic exchange of the resistance markers was analysed after co-cultivation of homologous and heterologous strains in vitro and in vivo during experimental infection of chickens. Double-resistant recombinants were obtained both in vitro and from the chicken intestine for all combinations of strains tested. Bidirectional genetic exchange of DNA between homologous and heterologous strains was confirmed by Southern blotting in combination with flaA polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP), amplified fragment length polymorphism (AFLP) and pulsed field gel electrophoresis (PFGE). Extensive PFGE analyses of isolated recombinants indicated the frequent occurrence of genetic rearrangements during the experimental infection, in addition to the homologous recombination of the antibiotic resistance genes. Together, the data indicate unequivocally that interstrain genetic exchange as well as intragenomic alterations do occur in vivo during C. jejuni infection. These events probably explain the genome plasticity observed for this pathogen.

Although symmetrical polyarticular amyloidosis has been described extensively in brown layers, spontaneous unilateral amyloid arthropathy has not been described previously in chickens. Birds from nine flocks of broiler parent stock (PS) had unilateral lameness associated with severe swelling of the left hock joint and the caudal aspect of the metatarsus. Gross pathology was restricted to the left hock joint and the left digital flexor tendons in almost all cases, suggesting an association with administration of Marek's disease vaccine. Amyloid deposits were found in 83% (25/30) of affected joints by histological examination of Congo red stained sections. Systemic amyloidosis, involving mainly the liver and spleen, was found in 59% (10/17) of birds. Enterococcus faecalis was isolated from joints in 77% (23/30) of cases and Staphylococcus aureus was isolated from the joint in one case (1/30). Thirty-five E. faecalis isolates from joints, tendons and blood samples from birds in five affected PS flocks were compared using pulsed-field gel electrophoresis (PFGE) to separate genomic fragments after digestion with Sma I. All but one isolate had identical or closely related restriction endonuclease digestion (RED) patterns that were very similar to a known arthropathic and amyloidogenic E. faecalis isolate. A further 30 E. faecalis isolates from seven grandparent stock (GPS) flocks and two isolates from two unaffected PS flocks of the same genetic background were analysed by PFGE. Among these isolates, 11 originating from four GPS flocks had RED patterns identical to or closely related to the reference amyloid-inducing strain. Moreover, one E. faecalis isolate from amyloidotic joints of brown layers housed in California, USA was included in the analysis and appeared to be identical to the reference strain. This study showed that the E. faecalis isolates involved in these outbreaks of unilateral amyloid arthropathy in broiler breeders belonged to the same clone as that responsible for outbreaks in brown layers.

1. In previous studies, a lack of agreement in measurements of plasma corticosterone concentrations and heterophil:lymphocyte (H/L) ratio as physiological indices of stress, caused by hunger and frustration in restricted-fed broiler breeders, was observed. It could be suggested that the differences between previous studies were caused by differences in duration of restriction and time of the day of the measurements. Therefore, in the present study the plasma corticosterone concentration and the H/L ratio were again determined in restricted- and ad libitum-fed growing broiler breeders, taking possible causes of disagreement between previous studies into account. In addition, we measured the daily rhythm in body temperature and heart rate, and the corticosterone responses to an acute stressor as physiological indices of stress. 2. Female broiler breeders (64 per treatment, housed in groups of 4 birds) were used in the experiment. Behaviour, baseline plasma corticosterone concentrations and H/L ratio were determined at 21 d of age (immediately after the start of food restriction), and at 42 and 63 d of age. Body temperature, heart rate and activity were measured by radiotelemetry for 36 h at 49 and 70 d of age. In addition, the plasma corticosterone response to acute stress (5 min manual restraint) was measured at 77 or 78 d of age. 3. Restricted broiler breeders had higher plasma corticosterone concentrations at 42 and 63 d of age, but no differences in H/L. ratio were found between restricted birds and unrestricted control birds. Restricted broiler breeders had a higher corticosterone response to 5 min manual restraint than unrestricted birds. Restricted birds displayed a clear day-night rhythm in body temperature, heart rate and activity whereas such a rhythm was blunted in ad libitum-fed birds. 4. It is discussed that some physiological differences (plasma corticosterone concentrations, body temperature and heart rate) between ad libitum-fed and restricted broiler breeders may have been caused by differences in metabolic rate as well as by differences in the level of stress. It is concluded that a combination of behavioural measurements and a wide range of physiological parameters should be used for the assessment of stress in growing broiler breeders.

This study was designed to identify risk factors for intramammary infections with Streptococcus uberis and Staphylococcus aureus under field conditions. An 18-mo survey with sampling of all quarters of all lactating cows at 3-wk intervals was carried out in three Dutch dairy herds with medium bulk milk somatic cell count (200,000 to 300,000 cells/ml). Quarter milk samples were used for bacteriology and somatic cell counting. Data on parity, lactation stage, and bovine herpesvirus 4-serology were recorded for each animal. During the last year of the study, body condition score, and teat-end callosity scores were recorded at 3-wk intervals. A total of 93 new infections with Strep. uberis were detected in 22,665 observations on quarters at risk for Strep. uberis infection, and 100 new infections with Staph. aureus were detected in 22,593 observations on quarters at risk for Staph. aureus infection. Multivariable Poisson regression analysis with clustering at herd and cow level was used to identify risk factors for infection. Rate of infection with Strep. uberis was lower in first- and second-parity cows than in older cows, and depended on stage of lactation in one herd. Quarters that were infected with Arcanobacterium pyogenes or enterococci, quarters that had recovered from Strep. uberis- or Staph. aureus-infection in the past, and quarters that were exposed to another Strep. uberis infected quarter in the same cow had a higher rate of Strep. uberis infection. Teat-end callosity and infection with coagulase-negative staphylococci or corynebacteria were not significant as risk factors. Rate of Staph. aureus infection was higher in bovine herpesvirus 4-seropositive cows, in right quarters, in quarters that had recovered from Staph. aureus or Strep. uberis infection, in quarters exposed to other Staph. aureus infected quarters in the same cow, and in quarters with extremely callused teat ends. Infection with coagulase-negative staphylococci was not significant as a risk factor. The effect of infection with corynebacteria on rate of infection with Staph. aureus depended on herd, stage of lactation, and teat-end roughness. Herd level prevalence of Strep. uberis or Staph. aureus, and low quarter milk somatic cell count were not associated with an increased rate of infection for Strep. uberis or Staph. aureus.