Link with Innate Immune System Uncovered

Gangrenous dermatitis (GD) is a disease with increasing economic importance, explained G.X. Li of Animal Parasitic Diseases Laboratory, ANRI, ARS-USDA in Beltsville, Maryland, working with co-authors in a number of research centres. They were able to document changes associated with the innate immune response to Clostridium pathogens in GD in broiler chickens.

Their study investigated pathological and immunological changes, and molecular diagnosis associated with GD outbreaks in broilers.

Ten birds with clinical GD symptoms and five control birds, which appeared to be clinically healthy were selected for sample collection to measure nitric oxide (NO), acute phase protein (AGP), tissues for histology and immunohistochemistry and cytokine transcripts.

Li explained that the GD birds demonstrated typical clinical symptoms, gross lesions at necropsy including discoloration of skin around the breast, abdomen, and wings with congestion, necrosis and emphysema (gas accumulation), discoloration of muscle with sero-sanguineous fluid, and fibro-necrotic enteritis. Histopathological findings included haemorrhagic lesions, degeneration and necrosis of parenchymatous cells, especially of skin, muscle, and intestine.

Immunofluorescence staining revealed Clostridium-like bacilli in the skin and intestine. C. perfringens (CP) and C. septicum (CS) genomic sequences were identified by PCR in samples from skin, muscle and intestine. Serological analysis demonstrated that both diseased and healthy birds had high antibody titres against CP, CS, Eimeria, chick anaemia virus and infectious bursal disease virus.

Mitogen (ConA, LPS)-driven splenic lymphocyte proliferation was significantly depressed in GD birds compared to control birds and GD chickens produced higher levels of serum NO and AGP. Flow cytometric analysis of lymphocyte sub-populations showed a number of positive cells in the skin, and in the intestine of GD birds. The expression levels of mRNAs encoding pro-inflammatory and chemokines were increased in GD birds.

Li and co-authors said their results provide histological, immunological and molecular changes associated with GD infection in broiler birds, especially document changes associated with innate immune response to Clostridium pathogens in GD in broiler chickens.

Natural Solution for Gangrenous Dermatitis Shows Promise

Mellencamp and colleagues at Ralco Nutrition reported benefits of a combination of oregano essential oil combined with a novel prebiotic fibre on growth and livability of broilers on a farm with gangrenous dermatitis.

In their paper, they stressed that a healthy gastrointestinal tract is critical for optimum broiler growth as it allows maximum nutrient absorption and acts as the first line of defence against disease.

It has previously been found that prebiotic fibres promote a balanced microflora by preferentially supporting Bifidobacteria and Lactobacillus species. These beneficial bacteria produce short chain fatty acids that reduce pH and support the gut mucosal barrier. They continued that overgrowth of pathogenic bacteria – such as E. coli and Clostridium perfringens – is less likely when the gut microflora is established early post-hatch.

Oregano essential oil (OEO) is a natural feed flavouring with potent anti-microbial activity that has been shown to improve broiler performance on farms with enteric challenges, explained Mellencamp.

Their study investigated the effects of OEO combined with a hemicellulose prebiotic fibre on performance of six-pound broilers on a farm with a history of dermatitis.

Two control houses (24,400 birds per house) received a rigorous in-feed anti-coccidial programme with an antibiotic growth promoter (AGP). The two test houses (n=24,400 birds per house) received OEO (Regano® 500) and a new hemicellulose prebiotic fibre product (NutriFibe^TM Complex).

The results showed that the test group delivered growth and performance that was equal to the controls. Control birds weighed 6.16lb at 42 days compared with 6.15lb for the test group.

Differences were observed in disease control, they said. Birds in one control house showed signs of dermatitis at day 35, with a mortality rate of 3.1 per cent. Death loss in the other control house was 1.9 per cent with no evidence of dermatitis. Both the test houses were free from dermatitis and had mortality rates of 2.3 per cent and 2.9 per cent.

The researchers concluded that the results show that the product combination delivered broiler performance that was equal to a rigorous chemical and AGP programme. They added that the absence of dermatitis in the test houses is an encouraging result and warrants further investigation.

References

Li G.X., H.S. Lillehoj, K.W. Lee, S.H. Jang, P. Marc, D. Ritter, D.A. Bautista, A.P. Neumann, T.G. Rehberger and G.R. Siragusa. 2010. Histopathology, immunohistochemistry and cytokine production associated with gangrenous dermatitis outbreaks in broiler farms. Proceedings of International Poultry Scientific Forum 2010, Atlanta, US. M63.

Mellencamp M.A., R. Smith and R. Dvorak. 2010. Effects of oregano essential oil combined with a novel prebiotic fiber on growth and livability of broilers on a farm with gangrenous dermatitis. Proceedings of International Poultry Scientific Forum 2010, Atlanta, US. M64.

Further Reading

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You can view our previous report from IPSF 2010 by clicking here.

March 2010