Behavioral patterns as indicators of resilience after parturition in dairy cows.

During the transition phase, dairy cows are susceptible to develop postpartum diseases. Cows that stay healthy or recover rapidly can be considered to be more resilient in comparison to those that develop postpartum diseases. An indication of loss of resilience will allow for early intervention with preventive and supportive measures before the onset of disease. We investigated which quantitative behavioral characteristics during the dry period could be used as indicators of reduced resilience after calving, using noninvasive Smart Tag neck and Smart Tag leg sensors in dairy cows (Nedap N.V.). We followed 180 cows during 2 wk before until 6 wk after parturition at 4 farms in the Netherlands. Serving as proxy for loss of resilience, as defined by the duration and severity of disease, a clinical assessment was performed twice weekly and blood samples were taken in the first and fifth week after parturition. For each cow, clinical and serum value deviations were aggregated into a total deficit score (TDS total). We also calculated TDS values relating to inflammation, locomotion, or metabolic problems, which were further divided into macro-mineral and liver-related deviations. Smart Tag neck and leg sensors provided continuous behavioral activity signals of which we calculated the average, variance, and autocorrelation during the dry period. Diurnal patterns in the behavioral activity signals were derived by fast Fourier transformation and the calculation of the nonperiodicity. To select significant predictors of resilience, we first performed a univariate analysis with TDS as dependent variable and the behavioral characteristics that were measured during the dry period, as potential predictors with cow as experimental unit. We included parity group as fixed effect and farm as random effect. Next, we performed multivariable analysis with only significant predictors, followed by a variable selection procedure to obtain a final linear mixed model with an optimal subset of predictors with parity group as fixed effect and farm as random effect. The TDS total was best predicted by average inactive time, nonperiodicity ruminating, nonperiodicity of bouts standing up and fast Fourier transformation stand still. Average inactive time was negatively correlated with average eating time, and these 2 predictors could be exchanged with only little difference in model performance. Our best performing model predicted TDS total at a cutoff level of 60 points, with a sensitivity of 79.5% and a specificity of 73.2% with a positive predicted value of 0.69 and a negative predicted value of 0.83. The models to predict the other TDS categories showed a lower predictive performance as compared with the TDS total model, which could be related to the limited sample size and therefore, low occurrence of problems within a specific TDS category. Furthermore, more resilient dairy cows are characterized by high averages of eating time with high regularity in rumination and low averages of inactive time. They reveal high regularity in standing time and transitions from lying to standing, in the dry period. These behaviors can be used as indicators of resilience and allow for preventive intervention during the dry period in vulnerable dairy cattle. However, further examination is still required to find clues for adequate intervention strategies.

Host genotype affects endotoxin release in excreta of broilers at slaughter age.

Host genotype, early post-hatch feeding, and pre- and probiotics are factors known to modulate the gut microbiome. However, there is a knowledge gap on the effect of both chicken genotype and these dietary strategies and their interplay on fecal microbiome composition and diversity, which, in turn, can affect the release of endotoxins in the excreta of broilers. Endotoxins are a major concern as they can be harmful to both animal and human health. The main goal of the current study was to investigate whether it was possible to modulate the fecal microbiome, thereby reducing endotoxin concentrations in the excreta of broiler chickens. An experiment was carried out with a 2 × 2 × 2 factorial arrangement including the following three factors: 1) genetic strain (fast-growing Ross 308 vs. slower growing Hubbard JA757); 2) no vs. combined use of probiotics and prebiotics in the diet and drinking water; and 3) early feeding at the hatchery vs. non-early feeding. A total of 624 Ross 308 and 624 Hubbard JA757 day-old male broiler chickens were included until d 37 and d 51 of age, respectively. Broilers (N = 26 chicks/pen) were housed in a total of 48 pens, and there were six replicate pens/treatment groups. Pooled cloacal swabs (N = 10 chickens/pen) for microbiome and endotoxin analyses were collected at a target body weight (BW) of 200 g, 1 kg, and 2.5 kg. Endotoxin concentration significantly increased with age (p = 0.01). At a target BW of 2.5 kg, Ross 308 chickens produced a considerably higher amount of endotoxins (Δ = 552.5 EU/mL) than the Hubbard JA757 chickens (p < 0.01). A significant difference in the Shannon index was observed for the interaction between the use of prebiotics and probiotics, and host genotype (p = 0.02), where Ross 308 chickens with pre-/probiotics had lower diversity than Hubbard JA757 chickens with pre-/probiotics. Early feeding did not affect both the fecal microbiome and endotoxin release. Overall, the results suggest that the chicken genetic strain may be an important factor to take into account regarding fecal endotoxin release, although this needs to be further investigated under commercial conditions.

Antibiotics in 16-day-old broilers temporarily affect microbial and immune parameters in the gut.

Animal health benefits from a stable intestinal homeostasis, for which proper development and functioning of the intestinal microbiota and immune system are essential. It has been established that changes in microbial colonization in early life (the first 2 wk post hatch) impacts the functioning of the adult gut and the associated crosstalk between microbiota and intestinal mucosal cells. The aim of the present study was to study the effect of the administration of antibiotics later in life (d 15 to 20 post hatch) on microbiota and immune parameters. For this purpose, chickens received from 15 d post hatch during 5 d amoxicillin or enrofloxacin through their drinking water. Before and at 6, 16, and 27 d after start of the administration of antibiotics, the composition of the microbiota in the jejunum was determined using a 16S ribosomal RNA gene-targeted DNA microarray, the CHICKChip. At 6 d after the start of the administration of the antibiotics, the composition and diversity of the microbiota were affected significantly (P < 0.05), but this change was small and observed only temporarily since differences disappeared at 16 d after initiating treatment with amoxillin and at 27 d after starting treatment with enrofloxacin. Intestinal morphology and development were not visibly affected since there were no differences between villus/crypt ratios and numbers of PAS+ and PCNA+ cells in the duodenum and jejunum at any time point. At 16 d after the start of antibiotic administration, the number of CD4+ T-cells and CD8+ T-cells in the duodenum was lower compared to the control animals; however, this difference was not significant. At some time points, significant differences (P < 0.05) were observed among the groups to locally expressed IL-8, IL-1ß, IFN-γ, IL-2, and IL-4 mRNA. However, this effect was not long lasting, as differences that were observed at 16 d after starting the treatment had disappeared at 27 d after treatment was started. The results of this study indicate that later in the broiler's life, antibiotics only temporarily affect intestinal microbial and immune parameters.

Modelling the Innate Immune Response against Avian Influenza Virus in Chicken.

At present there is limited understanding of the host immune response to (low pathogenic) avian influenza virus infections in poultry. Here we develop a mathematical model for the innate immune response to avian influenza virus in chicken lung, describing the dynamics of viral load, interferon-α, -ß and -γ, lung (i.e. pulmonary) cells and Natural Killer cells. We use recent results from experimentally infected chickens to validate some of the model predictions. The model includes an initial exponential increase of the viral load, which we show to be consistent with experimental data. Using this exponential growth model we show that the duration until a given viral load is reached in experiments with different inoculation doses is consistent with a model assuming a linear relationship between initial viral load and inoculation dose. Subsequent to the exponential-growth phase, the model results show a decline in viral load caused by both target-cell limitation as well as the innate immune response. The model results suggest that the temporal viral load pattern in the lungs displayed in experimental data cannot be explained by target-cell limitation alone. For biologically plausible parameter values the model is able to qualitatively match to data on viral load in chicken lungs up until approximately 4 days post infection. Comparison of model predictions with data on CD107-mediated degranulation of Natural Killer cells yields some discrepancy also for earlier days post infection.

Differences in highly pathogenic avian influenza viral pathogenesis and associated early inflammatory response in chickens and ducks.

We studied the immunological responses in the lung, brain and spleen of ducks and chickens within the first 7 days after infection with H7N1 highly pathogenic avian influenza (HPAI). Infection with HPAI caused significant morbidity and mortality in chickens, while in ducks the infection was asymptomatic. The HPAI viral mRNA load was higher in all investigated tissues of chickens compared with duck tissues. In the lung, brain and spleen of HPAI-infected chickens, a high, but delayed, pro-inflammatory response of IL-6 and IL-1ß mRNA was induced, including up-regulation of IFN-ß, IFN-γ, TLR3 and MDA-5 mRNA from 1 day post infection (p.i.). Whereas in ducks already at 8 h p.i., a quicker but lower response was found for IL-6, IL-1ß and iNOS mRNA followed by a delayed activation of TLR7, RIG-I, MDA5 and IFN-γ mRNA response. Virus-infected areas in the lung of chickens co-localized with KUL-01⁺ (macrophages, dendritic cells), CD4⁺, and CD8α⁺ cells, during the first day after infection. However, only KUL-01⁺ cells co-localized with the virus after 1 day p.i. In ducks, CVI-ChNL-68.1⁺ (macrophage-like cells), CD4⁺ and CD8α⁺ cells and apoptosis co-localized with the virus within 8 h p.i. Apoptosis was detected in the brain and lung of HPAI-infected chickens after 2 days p.i. and apoptotic cells co-localized with virus-infected areas. In conclusion, excessive delayed cytokine inflammatory responses but inadequate cellular immune responses may contribute to pathogenesis in chickens, while ducks initiate a fast lower cytokine response followed by the activation of major pattern recognition receptors (TLR7, RIG-I, MDA5) and a persistent cellular response.

Q fever diagnosis and control in domestic ruminants.

Q fever is a zoonosis caused by the bacterium Coxiella burnetii, a highly infectious agent that can survive in the environment. Therefore, Q fever has a major public health impact when outbreaks occur. Small ruminants are identified as the source in the majority of outbreaks in humans. Accurate diagnosis and effective control strategies are necessary to limit the zoonotic and veterinary impact of Q fever. For this, knowledge of the pathogenesis of Q fever and excretion routes of C. burnetii from infected animals is crucial. Abortions as well as normal parturitions in infected small ruminants are the most important excretion routes of C. burnetii. Excretion of C. burnetii via faeces and vaginal mucus has also been suggested. However, contamination of these samples by bacteria present in the environment may influence the results. This hampers the accurate identification of infected animals by these samples; however, the detection of C. burnetii in milk samples seems not to be influenced by environmental contamination. Q fever in animals can be detected by direct (immunohistochemistry and PCR) and indirect (complement fixation test (CFT), enzyme- linked immunosorbent assay (ELISA) and indirect immunofluorescence assay (IFA) methods. A combination of both direct and indirect methods is recommended in current protocols to detect Q fever on herd level. For the control of Q fever in domestic animals, vaccination with a phase 1 C. burnetii whole cell inactivated vaccine is reported to be effective in preventing abortion and reducing bacterial shedding, especially after several years of administration. Vaccination might not be effective in already infected animals nor in pregnant animals. Furthermore, the complicated vaccine production process, requiring biosafety level 3 facilities, could hamper vaccine availability. Future challenges include the development of improved, easier to produce Q fever vaccines.

A mathematical model representing cellular immune development and response to Salmonella of chicken intestinal tissue.

The aim of this study was to create a dynamic mathematical model of the development of the cellular branch of the intestinal immune system of poultry during the first 42 days of life and of its response towards an oral infection with Salmonella enterica serovar Enteritidis. The system elements were grouped in five important classes consisting of intra- and extracellular S. Enteritidis bacteria, macrophages, CD4+, and CD8+ cells. Twelve model variables were described by ordinary differential equations, including 50 parameters. Parameter values were estimated from literature or from own immunohistochemistry data. The model described the immune development in non-infected birds with an average R² of 0.87. The model showed less accuracy in reproducing the immune response to S. Enteritidis infection, with an average R² of 0.51, although model response did follow observed trends in time. Evaluation of the model against independent data derived from several infection trials showed strong/significant deviations from observed values. Nevertheless, it was shown that the model could be used to simulate the effect of varying input parameters on system elements response, such as the number of immune cells at hatch. Model simulations allowed one to study the sensitivity of the model outcome for varying model inputs. The initial number of immune cells at hatch was shown to have a profound impact on the predicted development in the number of systemic S. Enteritidis bacteria after infection. The theoretical contribution of this work is the identification of responses in system elements of the developing intestinal immune system of poultry obtaining a mathematical representation which allows one to explore the relationships between these elements under contrasting environmental conditions during different stages of intestinal development.

Increased pathogenicity of European porcine reproductive and respiratory syndrome virus is associated with enhanced adaptive responses and viral clearance.

Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically important diseases of swine worldwide. Since its first emergence in 1987 the PRRS virus (PRRSV) has become particularly divergent with highly pathogenic strains appearing in both Europe and Asia. However, the underlying mechanisms of PRRSV pathogenesis are still unclear. This study sets out to determine the differences in pathogenesis between subtype 1 and 3 strains of European PRRSV (PRRSV-I), and compare the immune responses mounted against these strains. Piglets were infected with 3 strains of PRRSV-I: Lelystad virus, 215-06 a British field strain and SU1-bel from Belarus. Post-mortem examinations were performed at 3 and 7 days post-infection (dpi), and half of the remaining animals in each group were inoculated with an Aujeszky's disease (ADV) vaccine to investigate possible immune suppression resulting from PRRSV infection. The subtype 3 SU1-bel strain displayed greater clinical signs and lung gross pathology scores compared with the subtype 1 strains. This difference did not appear to be caused by higher virus replication, as viraemia and viral load in broncho-alveolar lavage fluid (BALF) were lower in the SU1-bel group. Infection with SU1-bel induced an enhanced adaptive immune response with greater interferon (IFN)-γ responses and an earlier PRRSV-specific antibody response. Infection with PRRSV did not affect the response to vaccination against ADV. Our results indicate that the increased clinical and pathological effect of the SU1-bel strain is more likely to be caused by an enhanced inflammatory immune response rather than higher levels of virus replication.

Differential innate responses of chickens and ducks to low-pathogenic avian influenza.

Ducks and chickens are hosts of avian influenza virus, each with distinctive responses to infection. To understand these differences, we characterized the innate immune response to low-pathogenicity avian influenza virus H7N1 infection in chickens and ducks. Viral RNA was detected in the lungs of chickens from day 0.8 to 7, in ducks mainly at day 4. In both species, viral RNA was detected in the bursa and gut. Infection in chickens resulted in up-regulation of interferon (IFN)-α and IFN-ß mRNA, while in the ducks IFN-γ mRNA was strongly up-regulated in the lung and bursa. In chickens and ducks, all investigated pathogen recognition receptor (PRR) mRNAs were up-regulated; however, in the chicken lung Toll-like receptor (TLR)7 and melanoma differentiation-associated protein (MDA)-5 mRNA were strongly induced. TLR3, TLR7 and MDA-5 responses correlated with IFN-α and IFN-ß responses in chickens, but in ducks a correlation between IFN-α and TLR7, retinoic acid-inducible gene-I and MDA-5 was absent. We studied the responses of duck and chicken splenocytes to poly(I:C) and R848 analogues to analyse the regulation of PRRs without the interfering mechanisms of the influenza virus. This revealed IFN-α and IFN-γ responses in both species. MDA-5 was only strongly up-regulated in chicken splenocytes, in which time-related PRR responses correlated with the IFN-α and IFN-ß response. This correlation was absent in duck splenocytes. In conclusion, chickens and ducks differ in induction of MDA-5, TLR7 and IFN-α mRNA after an influenza virus infection in vivo and after in vitro stimulation with TLR antagonists.

Differences in the early response of hatchlings of different chicken breeding lines to Salmonella enterica serovar Enteritidis infection.

Poultry products are the major source of food-borne Salmonella infection in humans. Broiler lines selected to be more resistant to Salmonella could reduce the transfer of Salmonella to humans. To investigate differences in the susceptibility of newly hatched chicks to oral infection with Salmonella enterica serovar Enteritidis, 3 commercial broiler lines (A, B, and C) were infected immediately after hatch and compared to healthy controls at 0.33, 1, and 2 d postinfection. Weight, bacteriological examination, and the jejunal influx of CD4, CD8, TCRαß, TCRγδ, and KUL01 (macrophages and dendritic cells) cells that are positive was investigated. In addition, the jejunal transcriptional response was analyzed using whole-genome chicken cDNA arrays. Salmonella colony-forming unit counts from cecal content and liver revealed that Salmonella enterica entered the body at 0.33 d postinfection. Broiler line A appeared most susceptible to intestinal colonization and the systemic spread of Salmonella. In addition, the Salmonella-induced jejunal influx of macrophages in this line showed a clear increase in time, which is in contrast to lines B and C. On the other hand, all lines showed a peak of CD4(+) cells at 1 d postinfection when infected chicks were compared to control chicks. The transcriptional response of line A clearly differed from the responses in lines B and C. Functional analysis indicated that the majority of the differentially expressed genes at 0.33 d postinfection in line A were involved in cell-cycle functions, whereas at 2 d postinfection the majority of the differentially expressed genes could be assigned to inflammatory disorder, differentiation and proliferation of (T) lymphocytes. These data indicate that hatchlings of different broiler lines differ in their systemic spread of Salmonella and suggest that intestinal barrier functions, as well as immunological responses, may be the underlying factors. We hypothesize that the differences between genetic chicken lines divergent in their response to Salmonella infection at a young age include developmental differences of the gut.

Effect of Eimeria acervulina infection history on the immune response and transmission in broilers.

Heterogeneity in exposure to Eimeria spp. of chickens in a flock will result in differences between individual birds in oocyst output and acquired immunity, which subsequently affects transmission of the parasite in the population. The aim of this study was to quantify effects of previous infection of broilers with Eimeria acervulina on immune responses, oocyst output and transmission. A transmission experiment was carried out with pair-wise housed broilers, that differed in infection history. This "infection history" was achieved by establishment of a primary infection by inoculation of birds with 50,000 sporulated E. acervulina oocysts at day 6 of age ("primed"); the other birds did not receive a primary infection ("naïve"). The actual transmission experiment started at day 24 of age: one bird (I) was inoculated with 50,000 sporulated oocysts and was housed together with a non-inoculated contact bird (C). Oocyst excretion and parameters describing transmission, i.e. the number of infected C birds and time passed before start of excretion of C birds, were determined from day 28 to day 50 for six pairs of four different combinations of I and C birds (I-C): naïve-naïve, naïve-primed, primed-naïve and primed-primed. Immune parameters, CD4(+), CD8(+), αßTCR(+) and γδTCR(+) T cells and macrophages in duodenum, were determined in an additional 25 non-primed, non-inoculated control birds, and in the naïve-naïve and naïve-primed groups, each group consisting of 25 pairs. Although the numbers of CD4(+) T cells and γδTCR(+) T cells increased after primary infection, none of the immunological cell types provided an indication of differences in infectivity, susceptibility or transmission between birds. Oocyst output was significantly reduced in primed I and C birds. Transmission was reduced most in the primed-primed group, but nonetheless transmission occurred in all groups. This study also showed that acquired immunity significantly reduced oocyst output after inoculation and contact-infection, but not sufficiently to prevent transmission to contact-exposed birds.

Host response to simultaneous infections with Eimeria acervulina, maxima and tenella: a cumulation of single responses.

It is well known that broilers may be infected by different Eimeria strains at the same time and that different species infect specific parts of the gut. Cell mediated responses play a major role in the immune response in broilers after infection with Eimeria species. The cell mediated responses could be intestinal site specific and if this site specific cell mediated responses differ when other parts of the intestine are infected is unknown. To investigate this in the Eimeria infection model we analyzed the cell mediated responses to an infection with a single Eimeria species and with a mixture of different species of Eimeria such as E. acervulina, E. maxima or E. tenella in the duodenum, jejunum and caecum. The immune parameters we measured were intestinal T-cell and macrophage population dynamics as well as local cytokine mRNA expression. These parameters were related to the amount of Eimeria DNA that was measured in the intestine with an Eimeria strain specific quantitative PCR. The results showed that the strongest immune response was induced in the specific part of the intestine that was affected by each Eimeria strain. An E. acervulina infection mainly induced a duodenal CD8(+) T-cell and macrophage response as well as an increased IL-2, IL-4, IL-8, IL-10, and INF-gamma response. An E. maxima infection mainly induced a CD4(+) T-cell and macrophage response but also an increased IL-4, IL-8, and very strong INF-gamma (300-fold) expression in duodenum and jejunum. E. tenella induced a CD4(+) T-cell, macrophage response and an increase in the IL-2, IL-4, IL-8, IL-10, IL-18 and INF-gamma response in the caecum. The infection with a mixture of Eimeria species resulted in responses per intestinal segment that were similar to that observed following the single species infection. No synergistic or competitive effects were thus observed following a primary infection with a mixture of Eimeria species. In contrast, we observed an accumulation of the local effects of the single infections.

Exploiting genomics to improve animal health.

The research area of animal genomics is moving now from its sequencing era into an integrativefunctional genomics era. Thefast growing sequence information of animal genomes provides exiting opportunities for improving animal health traits by genomics-assisted breeding approaches. In addition, data from functional genomics studies offers deeper insight into the biological mechanisms that underlie animal health phenotypes. Understanding host-pathogen relationships, for example, promises to forward the integration of health genetics into breeding programmes and the development of new tools and strategies for the diagnosis, prognosis, treatment and prevention of infectious diseases. Similarly, increased knowledge on nutrient-gene interactions provides information on the effects of nutrients on biological processes. This knowledge may be used to redefine and optimize the nutritional needs of healthy animals. In this paper, prospects, challenges, and requirements of animal genomics research for improving animal health will be presented.

A pathway analysis tool for analyzing microarray data of species with low physiological information.

Pathway information provides insight into the biological processes underlying microarray data. Pathway information is widely available for humans and laboratory animals in databases through the internet, but less for other species, for example, livestock. Many software packages use species-specific gene IDs that cannot handle genomics data from other species. We developed a species-independent method to search pathways databases to analyse microarray data. Three PERL scripts were developed that use the names of the genes on the microarray. (1) Add synonyms of gene names by searching the Gene Ontology (GO) database. (2) Search the Kyoto Encyclopaedia of Genes and Genomes (KEGG) database for pathway information using this GO-enriched gene list. (3) Combine the pathway data with the microarray data and visualize the results using color codes indicating regulation. To demonstrate the power of the method, we used a previously reported chicken microarray experiment investigating line-specific reactions to Salmonella infection as an example.

Immune responses to an Eimeria acervulina infection in different broilers lines.

The (T-cell) immune responses of two different broiler lines to a primary Eimeria acervulina infection were investigated. The lines used were a commercial fast-growing broiler line and a slow-growing type of broiler as used in organic farming. Seven-day-old broilers of both lines were infected with 5 x 10(4) oocysts of E. acervulina. The animals were weighed and a species-specific real-time PCR was used to quantify the total amount of parasites in the duodenum. In the fast-growing line, a lower parasite load was seen from day 4 onwards compared to the slow-growing line. In both lines the intestinal peak of Eimeria DNA was observed at day 5 post infection (p.i.). In the duodenum no increase in CD4(+) T-cells was found in both infected lines, but a fast increase in CD8(+) T-cells was observed in the fast-growing line. At day 3 p.i. in the slow-growing broilers an IL-18 mRNA response was observed. At day 4 p.i. strong IFN-gamma and IL-8 mRNA responses were found in both lines. No IL-4 mRNA responses were found in the duodenum. In conclusion, both lines have different growth rates and control and infected conditions. Based on the kinetics of observed phenomena a primary infection with E. acervulina in 7-day-old broilers seems to generate an early CD8alpha(+) response in fast-growing broilers compared to the slow-growing broilers. This difference in immune reaction after an E. acervulina infection could result in a different Eimeria load in the duodenum.

Immune responses in Eimeria acervulina infected one-day-old broilers compared to amount of Eimeria in the duodenum, measured by real-time PCR.

T-cell responses are supposed to be the major immune reactions in broilers infected with Eimeria. The nature of such T-cell responses is influenced by the species of Eimeria involved, age of the host, amount of parasites and the preceding infection history. In young chicks the intestine is still developing in length while the lymphocyte populations in the gut develop and differentiate. In chicks infected at young age the immune response may be different in quality as compared to responses in adults. We investigated the (T-cell) immune responses of young broilers to a primary Eimeria acervulina infection in relation to the number of parasites used for infection. In our experiment we infected one-day-old broilers with a low (5 x 10(2) oocysts) and a high (5 x 10(4) oocysts) dose of E. acervulina. We used a newly developed species specific real-time PCR to quantify total amount of parasites in the duodenum as the number of oocysts in faeces may not be representative for the exposure of the gut immune system. We characterized T-cell subsets in the duodenum by means of FACS-analyses, lymphocyte proliferation assays with spleen lymphocytes and the mRNA profiles of different cytokines (TGF-beta2, -4, IFN-gamma, IL-2, -6, -8 and -18) in the duodenum by means of real-time PCR. From day 5 p.i. broilers with a high dose of E. acervulina had a significantly lower body weight than the control group. No increase in CD4(+) cells, but a strong increase in CD8(+) cells was observed at days 7 and 9 p.i. in the duodenum of broilers infected with a high dose E. acervulina. IL-8 mRNA responses were observed after infection with low and with high infection doses, but no IFN-gamma and TGF-beta mRNA responses were found in the duodenum. The specific proliferative T-cell responses to a low infectious dose were not significantly different as compared to the control group. In conclusion, based on the kinetics of observed responses a primary infection with a high dose of E. acervulina in one-day-old broilers seems to generate an immune response that shows a peak at the time of oocyst excretion, whereas the immune response to a low dose is less explicit.

Cytokine responses in broiler lines that differ in susceptibility to malabsorption syndrome.

1. Based on earlier studies it was hypothesised that there is an immunological basis for the differences in susceptibility to malabsorption syndrome (MAS). A study was conducted to investigate base-line and MAS-induced cytokine levels in the intestine of broilers that differ in MAS susceptibility. 2. The transcription of cytokine mRNA in the intestine was quantified using a real-time polymerase chain reaction (PCR) method. At different time points after disease induction the intestines of broilers were investigated for expression of interleukin (IL)-2, IL-6, IL-8, IL-18 and interferon (IFN)-gamma. Age-matched non-MAS-induced chickens served as controls. 3. Control chickens from a MAS-resistant line had higher concentrations of mRNA for IL-2, IL-6, IL-18 and IFN-gamma in the small intestine while no difference between the lines was found for IL-8. After induction of MAS the relative amounts of IL-2, IL-6, IL-8 and IFN-gamma mRNA increased more in the intestines of the susceptible line than in the gut of the resistant line. 4. We suggest that differences in cytokine mRNA in the base-line situation and in MAS-induced conditions indicate a difference in immune response regulation in the two broiler lines. This difference in response could lead to the difference in susceptibility to MAS.

Differences in intestinal gene expression profiles in broiler lines varying in susceptibility to malabsorption syndrome.

Examination of the host gene expression response upon encounters with pathogens may provide insights into the cellular events following an infection. In addition, it may shed light on the basic mechanisms underlying differences in the susceptibility of the host. In this study gene expression in the chicken jejunum was investigated in 2 different broiler lines under control and malabsorption syndrome (MAS) affected conditions. The 2 broiler lines differ in their susceptibility for MAS. The gene expression was investigated at 6 different times postinoculation using a custom-made intestine specific cDNA microarray. More than 70 up- or downregulated genes were identified after a MAS inoculation in both broiler lines. However, the number of the up- and downregulated genes varied between the 2 lines, with more differences in expression in the most susceptible line. Marked differences were observed in expression profiles between the 2 broiler lines, in control as well as in the MAS affected birds. The microarray data were validated and confirmed by quantitative real time PCR. The differentially expressed genes included immune related genes, genes associated with food absorption, and genes that need to be characterized further before their role in MAS and MAS susceptibility can be understood.

Vitamin and trace mineral content in feed of breeders and their progeny: effects of growth, feed conversion and severity of malabsorption syndrome of broilers.

1. A study was conducted to investigate the effects of several vitamins and trace elements chickens and in chickens experimentally infected with malabsorption syndrome (MAS). 2. Vitamins and trace minerals in feed were varied. Breeders received either a basal amount of vitamins and trace minerals (low mix) or an increased amount (high mix). Their progeny also received either a low mix or a high mix. Effects of different breeder and broiler mix combinations on broiler performance, heamatology, spleen weight and humoral response were examined in control chickens. The effects of the different feeds and breeder, broiler combinations at the severity and recovery of MAS infection were also studied. 3. In general, the immune system can be stimulated by addition of vitamins and trace minerals, without affecting the growth potential of the controls. The number of leukocytes increased on d 1 in the broilers descended from breeders receiving high mix. The response to Newcastle disease virus boost was affected by the different amount of vitamins. 4. When breeders received a high mix the number of infiltrating polymorphonuclear leukocytes in the intestine was higher compared with breeders receiving basal amounts of minerals and vitamins. Also the recovery rate of intestinal lesions, cystic crypts of Lieberkühn and villus atrophy, as observed by histopathology, was faster in the groups where the breeders received high mix.