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CPRC Update: August 2008

Details of CPRC-supported research


September 11, 2008
By CPRC

Topics

Under one of its priority research
programs, Avian Gut Microbiology, the Canadian Poultry Research Council
(CPRC) has provided funding for a number of projects. Below are
summaries of the final reports for two of them:

Under one of its priority research programs, Avian Gut Microbiology, the Canadian Poultry Research Council (CPRC) has provided funding for a number of projects. Below are summaries of the final reports for two of them:

DETERMINING WHY NECROTIC ENTERITIS DEVELOPS
Clostridium perfringens is a bacterium commonly found in the gut of a variety of healthy animals, including chickens. However, it is also linked to necrotic enteritis (NE). There is relatively little information on how NE develops, especially in terms of the role C. perfringens plays, and why certain strains of the bacterium can cause disease. Dr. Patrick Boerlin and his team at the University of Guelph are determining which strains of C. perfringens are present in chickens and seeing if strain diversity changes when birds are suffering from NE.

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Diversity
Dr. Boerlin first looked at the diversity of C. perfringens strains on a commercial broiler farm. It was unexpectedly low. Similar studies in Europe, where antimicrobial use is restricted, show higher strain diversity. Dr. Boerlin suggests that the use of bacitracin may have skewed the C. perfringens population towards a few resistant strains.

Samples from field cases of NE (these birds did not receive antimicrobials) were then compared to those from flocks with no known history of the disease. C. perfringens strains from NE-positive birds and from healthy birds from the same barn were generally the same genetic type. However, different NE outbreaks were associated with genetically diverse strains. Almost all isolates from NE-positive birds also tested positive for the NetB toxin, which was recently implicated as a contributing factor in NE. Collectively, these results suggest that something can be transferred from one strain to another (such as the netB gene) thereby affecting a strain’s ability to cause NE.

Factors
Samples were also taken from birds that were challenged with C. perfringens to artificially cause NE. All the strains tested were netB positive, but the degree to which they caused disease varied. The implication here is that netB may only contribute to NE and that other factors (such as management practices) are involved in development of the disease. Further studies are planned to determine the effects of different management practices on C. perfringens populations.
Funding for this project was provided by CPRC and the Poultry Industry Council.

STUDYING THE EFFECTS OF ANTIBIOTIC USE
There are increasing concerns over the development of bacterial resistance to antibiotics. It is not clear if antibiotic use in poultry is a contributing factor, but it is clear that antibiotics have an effect on microbial populations in the chicken gut. It has also been shown that antibiotic use affects development of the chicken’s immune system. Drs. Joshua Gong at Agriculture and Agri-Food Canada and Shayan Sharif at the University of Guelph are leading a research program aimed at determining which microbes in the gut are most affected by antibiotics, and how these microbial changes affect the immune system.

Immune Response
Birds were fed either non-medicated diets or those supplemented with bacitracin or virginiamycin. Samples were taken from small and large intestines and microbial populations were compared. A number of bacterial groups were affected by the presence of the antibiotics, especially by virginiamycin. This antibiotic was used in a second experiment during which birds were immunized with various antigens. The presence of virginiamycin in the feed led to the enhancement of immune response to one of the antigens. This result is surprising and may provide some insight as to why low levels of antibiotics can improve broiler performance.

Several species of Lactobacillus bacteria were affected by the presence of virginiamycin in this study. Further, Lactobacillus acidophilus has been linked to increased immune response in chickens. It has been hypothesized that decreased numbers of L. acidophilus in the gut due to antibiotic use could have a negative effect on immune function in the bird. Results from this research suggest, however, that the use of virginiamycin does not negatively affect immune function in broilers. Work is ongoing to further characterize changes in immune system gene expression in response to antibiotics. This information will be crucial to finding ways to improve the chicken’s immune function, both to enhance the effectiveness of currently used antibiotics and to perhaps reduce the need for them in the future.

Funding for this project was provided by the CPRC, the Poultry Industry Council, Agriculture and Agri-Food Canada and the Natural Sciences and Engineering Research Council.

For more details on any CPRC activities, please contact Gord Speksnijder at The Canadian Poultry Research Council, 483 Arkell Road, R.R.  2, Guelph, Ont., N1H 6H8; phone 289-251-2990; fax 519-837-3584; e-mail info@cp-rc.ca; or visit us at www.cp-rc.ca .

The membership of the CPRC consists of the Chicken Farmers of Canada, the Canadian Hatching Egg Producers, the Canadian Turkey Marketing Agency, the Canadian Egg Marketing Agency and the Canadian Poultry and Egg Processors’ Council. CPRC’s mission is to address its members’ needs through dynamic leadership in the creation and implementation of programs for poultry research in Canada, which may also include societal concerns.