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New pathway may lead to improved probiotic products

More research needed to characterize and refine inoculum.

Transferring intestinal contents from older chickens to young chicks may improve both the growth of the young birds and the resistance to challenge by pathogenic bacteria, according to research funded by the U.S. Poultry & Egg Assn. (USPOULRY) and the USPOULTRY Foundation.

Dr. Brian Oakley and colleagues at the Western University of Health Sciences in Ponoma, Cal., and the U.S. Department of Agriculture's Agricultural Research Service recently completed a research project in which they studied how the transfer of intestinal contents from older chickens to chicks affected growth and pathogen resistance.

Oakley explained that the poultry gastrointestinal (GI) microbiome — the population of microbes living in the intestinal tract — has been established as a key element of poultry nutrition, growth and pathogen resistance.

The problem, from an industry perspective, remains how to translate basic research about the importance of the GI microbiome to specific products and/or husbandry practices, Oakley said. Because the GI microbiome is a very complex community with hundreds of microbial species, identifying the exact members responsible for desirable effects is challenging, he noted.

Therefore, this project took a community-based approach to test whether serial transfers of intestinal material could generate an effective source of inoculum to improve the growth and pathogen resistance of young chicks.

This research had two main objectives:

1. Monitor changes in the microbial community during serial passages of GI contents through multiple generations of chicks, and

2. Compare the immune responses, growth and pathogen resistance of chicks colonized with this inoculum versus chicks exposed to a diverse environmental community typical of commercial poultry rearing.

For the first objective, serial transfers of intestinal material from two-week-old birds to newly hatched chicks provided a relatively stable source of inoculum, Oakley said. In general, the microbial community reached a stable state after the first transfer.

For the second objective, exposing young chicks to a complex microbial community improved resistance to pathogen challenge — particularly Campylobacter jejuni and Salmonella enteriditis — compared to chicks that were not inoculated, but surprisingly, chicks inoculated with a community from used commercial poultry litter had bodyweight gains and pathogen resistance scores that were as good as or better than chicks inoculated with material serially transferred through multiple generations of birds, Oakley reported.

Sequencing-based characterizations of the transplanted material showed relatively high proportions of bacteria in a group called the Firmicutes.

This observation was consistent with previous characterizations of the chicken GI microbiome and led to an additional third phase of the project in which the researchers have begun to selectively cultivate and characterize some of these bacteria to produce a more defined inoculum.

Oakley said the results show that microbiome transplants to young chicks can have beneficial effects and that serial transfers of the microbiome can produce a relatively stable source of inoculum. For the full impact of these results to help the industry, further development is required to better characterize and propagate the inoculum and to understand exactly what mechanisms are driving the observed effects, he said.

Towards this goal, the research group has begun to use the data generated by this project to help build a library of bacterial strains that may have future value as defined probiotic feed additives.

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