The incidence of necrotic enteritis in turkeys is associated with farm, season and faecal Eimeria oocyst counts.

BACKGROUND: Specific studies on the epidemiology of necrotic enteritis in turkeys are absent in the literature. Necrotic enteritis is common in turkeys and a leading cause of use of therapeutic antibiotics. This study describes the incidence of necrotic enteritis in turkey farms, and the association between incidence and bird age, season, faecal oocyst counts, grow-out size and feed mill. RESULTS: Necrotic enteritis was diagnosed post mortem in 20.2 % of 545 grow-outs of commercial female and male B.U.T. 10 turkeys started during the years 2010-2016. 80 % of all cases occurred at four to seven weeks of age. Median (minimum-maximum) age at disease detection was 37 (18-115) days. Turkey age at detection was influenced by season, and varied from 33 days among grow-outs hatched in February to 42 days among those hatched in July-August. The incidence also varied with season, showing peak occurrence among grow-outs hatched during February-March and the lowest incidence in turkeys hatched in July-August. 59 % of all cases were detected in 25 % of the farms. The incidence per farm varied from below 4 to 59 %. A multilevel mixed-effects logistic regression model indicated clear impacts of farm and season on incidence, and border-line impacts of grow-out size and feed mill. Grow-outs diagnosed with necrotic enteritis had higher counts of faecal Eimeria oocysts than grow-outs without a diagnosis. This difference was particularly clear during the high-risk period at five to seven weeks of age. Necrotic enteritis was the cause of treatment with therapeutic antibiotics in 88.2 % of all cases of treatment. CONCLUSIONS: Our data indicate that necrotic enteritis incidence in turkeys can be substantially influenced by risk factors at farm level. The incidence showed two seasonal peaks; a moderate peak in turkeys hatched in October/November and a marked peak in turkeys hatched during February/March. Mitigation measures at the farm may therefore be of particular importance during these months in farms located in the Northern temperate zone. Measures which effectively reduce counts of faecal Eimeria oocyst are likely to be among the more promising actions to take both at the farm and at population level.

Effect of Feed Additives as Alternatives to In-feed Antimicrobials on Production Performance and Intestinal Clostridium perfringens Counts in Broiler Chickens.

Numerous non-antibiotic feed additives (alternatives to antibiotics, ATAs) have been marketed, but few have been evaluated under uniform testing conditions modelling commercial flocks. We compared 24 ATA treatments and the ionophorous coccidiostat narasin against a diet without any feed additives. Feed conversion ratio and body weight gain were registered from day 0 to 28 in Ross 308 chickens housed on litter floor. The chickens were challenged with Eimeria spp., and cecal Clostridium perfringens (CP) counts were investigated. Active components from all ATA classes had a positive impact on intestinal health or production performance. Whereas narasin had a strong CP-reducing effect in combination with performance-promoting impact, only two ATA treatments achieved significantly beneficial effects on CP counts as well as feed conversion during the time span following Eimeria challenge. Active components present in these two treatments include a Bacillus subtilis probiotic strain, short- and medium-chain fatty acids and Saccharomyces cerevisiae components. Different ATA classes had beneficial impact during distinct rearing phases and on specific performance targets, suggesting that optimizing combinations and use of active components can make ATAs even more useful tools in broiler rearing without the use of in-feed antimicrobials. Further studies of promising ATAs and ATA combinations are required.

Near-infrared spectroscopy detects woody breast syndrome in chicken fillets by the markers protein content and degree of water binding.

The muscle syndrome woody breast (WB) impairs quality of chicken fillets and is a challenge to the poultry meat industry. There is a need for online detection of affected fillets for automatic quality sorting in process. Near-infrared spectroscopy (NIRS) is a promising method, and in this study we elucidate the spectral properties of WB versus normal fillets. On a training set of 50 chicken fillets (20 normal, 30 WB), we measured NIR, nuclear magnetic resonance (NMR) T2 relaxation distributions, and crude chemical composition. NIRS could estimate protein in the fillets with an accuracy of ±0.64 percentage points. T2 distributions showed that there was a larger share of free water in WB fillets. This difference in water binding generated a shift and narrowing of the water absorption peak in NIR around 980 nm, quantified by a bound water index (BWI). The correlation between BWI and T2 distributions was 0.78, indicating that NIRS contains information about degree of water binding. Discriminant analysis showed that NIRS obtained 100% correct classification of normal versus WB on the training set, and 96% correct classification on a test set of 52 fillets. The main reason for why NIRS can successfully discriminate between WB and normal fillets is the methods sensitivity to both protein content and degree of water binding in the muscle, both established markers for WB. The classification model can be based on NIR spectra only, calibration against protein is not needed. The affected muscle tissue associated with the WB syndrome is unevenly distributed in the fillets, and this heterogeneity was characterized by NIRS and NMR. Clear differences in water binding properties were found between the superficial 1 cm layer and the deeper layer at 1 to 2 cm depth. Significant differences in protein estimates by NIRS at different measurement points along the chicken fillets were obtained for WB fillets. The findings suggest how to obtain optimal sampling with NIRS for best possible discrimination between WB and normal breast fillets.

Rapid on-line detection and grading of wooden breast myopathy in chicken fillets by near-infrared spectroscopy.

The main objective of this work was to develop a method for rapid and non-destructive detection and grading of wooden breast (WB) syndrome in chicken breast fillets. Near-infrared (NIR) spectroscopy was chosen as detection method, and an industrial NIR scanner was applied and tested for large scale on-line detection of the syndrome. Two approaches were evaluated for discrimination of WB fillets: 1) Linear discriminant analysis based on NIR spectra only, and 2) a regression model for protein was made based on NIR spectra and the estimated concentrations of protein were used for discrimination. A sample set of 197 fillets was used for training and calibration. A test set was recorded under industrial conditions and contained spectra from 79 fillets. The classification methods obtained 99.5-100% correct classification of the calibration set and 100% correct classification of the test set. The NIR scanner was then installed in a commercial chicken processing plant and could detect incidence rates of WB in large batches of fillets. Examples of incidence are shown for three broiler flocks where a high number of fillets (9063, 6330 and 10483) were effectively measured. Prevalence of WB of 0.1%, 6.6% and 8.5% were estimated for these flocks based on the complete sample volumes. Such an on-line system can be used to alleviate the challenges WB represents to the poultry meat industry. It enables automatic quality sorting of chicken fillets to different product categories. Manual laborious grading can be avoided. Incidences of WB from different farms and flocks can be tracked and information can be used to understand and point out main causes for WB in the chicken production. This knowledge can be used to improve the production procedures and reduce today's extensive occurrence of WB.

Epidemiologic aspects of necrotic enteritis in broiler chickens - disease occurrence and production performance.

Since future conventional broiler production can no longer rely upon in-feed antimicrobials (anticoccidials and antibiotic growth promoters), understanding the most important non-antimicrobial factors influencing occurrence of necrotic enteritis (NE) in poultry will become urgent. Solid population-based data on NE occurrence are scarce. Additionally, data on cholangiohepatitis (CPH) at slaughter is a useful indirect measurement of NE occurrence. Existing data suggest that coccidiosis and nutritional factors are among the most important determinants of NE occurrence. Dietary cereal contents and dietary level of animal proteins can both influence NE occurrence, but cereal composition may be more important because cereals constitute a larger portion of the diet. Losses associated with NE vary depending on the severity of the disease, but data indicate that the farmers' profit may be reduced on average with as much as one third during an epidemic of clinical disease.

Emergence of AmpC-producing Escherichia coli in the broiler production chain in a country with a low antimicrobial usage profile.

The aim of this study was to estimate the prevalence of cephalosporin-resistant Escherichia coli at the different levels of the Norwegian broiler production pyramid and identify the mechanisms responsible for the resistance phenotype. Samples from all levels of the broiler production pyramid and retail chicken meat (fillets) were included (n=649). The occurrence of cephalosporin-resistant E. coli at the different production levels ranged from 8 to 43%. All these isolates had an AmpC-phenotype, and the majority carried the blaCMY-2 gene. In addition, a few isolates with up-regulated chromosomal ampC were identified. The results show that Norway has a relatively high prevalence of cephalosporin-resistant E. coli in the broiler production chain in spite of a very low consumption of antimicrobial agents. Cephalosporins have not been used in the Norwegian broiler production, and it has been hypothesised that import of breeding animals and hatching eggs may be the source of these resistant bacteria. We demonstrate that these bacteria are disseminated in the production pyramid despite the lack of selection pressure from antimicrobial agents.

Molecular identification and characterization of novel coronaviruses infecting graylag geese (Anser anser), feral pigeons (Columbia livia) and mallards (Anas platyrhynchos).

In light of the finding of a previously unknown coronavirus as the aetiology of the severe acute respiratory syndrome (SARS), it is probable that other coronaviruses, than those recognized to date, are circulating in animal populations. Here, the results of a screening for coronavirus are presented, using a universal coronavirus RT-PCR, of the bird species graylag goose (Anser anser), feral pigeon (Columbia livia) and mallard (Anas platyrhynchos). Coronaviruses were found in cloacal swab samples from all the three bird species. In the graylag goose, 40 of 163 sampled birds were coronavirus positive, whereas two of 100 sampled pigeons and one of five sampled mallards tested positive. The infected graylag geese showed lower body weights compared with virus-negative birds, suggesting clinical significance of the infection. Phylogenetic analyses performed on the replicase gene and nucleocapsid protein sequences, indicated that the novel coronaviruses described in the present study all branch off from group III coronaviruses. All the novel avian coronaviruses harboured the conserved s2m RNA structure in their 3' untranslated region, like other previously described group III coronaviruses, and like the SARS coronavirus. Sequencing of the complete nucleocapsid gene and downstream regions of goose and pigeon coronaviruses, evidenced the presence of two additional open reading frames for the goose coronavirus with no sequence similarity to known proteins, but with predicted transmembrane domains for one of the encoded proteins, and one additional open reading frame for the pigeon coronavirus, with a predicted transmembrane domain, downstream of the nucleocapsid gene.

Maternal vaccination against subclinical necrotic enteritis in broilers.

The inclusion of antibacterial feed additives has until now been the major strategy for controlling Clostridium perfringens-associated necrotic enteritis in broilers. In the present study, the effect of maternal immunization against the disease was examined. Broiler breeder hens were injected intramuscularly with candidate vaccines based on C. perfringens type A and type C toxoids adjuvanted with aluminium hydroxide. Vaccination resulted in a strong serum immunoglobulin G response to C. perfringens alpha-toxin in parent hens, and specific antibodies were transferred to their progeny. Subclinical necrotic enteritis in broilers was induced under field conditions or in a disease model, and the occurrence of specific enteric and hepatic lesions was evaluated in randomly selected birds. In three experiments, estimates of odds ratio for developing such lesions were 0.23, 0.33 and 0.56 in maternally toxoid C-immunized broilers compared with non-immunized controls. In toxoid A-immunized birds, odds ratios were estimated at 0.41, 0.61 and 0.63. From these results, immunoprophylaxis seems to be an interesting alternative for the control of necrotic enteritis in broilers.

Diagnosing Clostridium perfringens-associated necrotic enteritis in broiler flocks by an immunoglobulin G anti-alpha-toxin enzyme-linked immunosorbent assay.

The tools available for monitoring necrotic enteritis caused by Clostridium perfringens in broiler chickens have been limited, particularly for identifying subclinical disease. In this study, a modified enzyme-linked immunosorbent assay was used to quantify levels of specific immunoglobulin G to C. perfringens alpha-toxin in serum from broilers. We found significantly higher antibody levels in broilers with a history of subclinical necrotic enteritis compared with a zinc-bacitracin-treated group with a low level of gut lesions. Furthermore, in 4.5-week-old commercial broiler flocks, there was an association between the occurrence of C. perfringens-associated hepatitis at slaughter and the immune response to alpha-toxin. Practical solutions for defining cut-off levels for positive serum samples at individual and flock levels are proposed, and were found to be useful on a set of samples available from flocks with different histories regarding the occurrence of C. perfringens-associated disease. This serological approach seems promising as a diagnostic tool in research and disease monitoring regarding C. perfringens-associated disease.