Evaluating bacterial colonization of a developing broiler embryo after in ovo injection with a bioluminescent bacteria

Authors: CASTANEDA, CLAUDIA - Mississippi State University; MCDANIEL, CHRISTOPHER - Mississippi State University; ABDELHAMED, HOSSAM - Mississippi State University; KARSI, ATTILA - Mississippi State University; KIESS, AARON - Mississippi State University

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2019
Publication Date: 2/21/2019
Citation: Castaneda, C., McDaniel, C., Abdelhamed, H., Karsi, A., Kiess, A. 2019. Evaluating bacterial colonization of a developing broiler embryo after in ovo injection with a bioluminescent bacteria. Poultry Science. 98(7):2997-3006. https://doi.org/10.3382/ps/pez053.
DOI: https://doi.org/10.3382/ps/pez053

Interpretive Summary: As animal agriculture moves away from using antibiotics as growth promoters, alternatives to antibiotics must be identified to assist with controlling disease outbreaks. Probiotics (beneficial micro-organisms) are considered to be an antibiotic alternative. Currently, probiotics are provided to broilers in their feed, however, young chicks may not make it to the feed for 24 to 48 h after they hatch from the egg. This time between hatch and their first meal provides pathogenic organisms an opportunity to colonize the chick potentially causing a disease outbreak. In ovo injection, an injection into the developing egg before hatch, may allow an opportunity for beneficial micro-organisms (probiotics) to colonize the broiler chick before environmental exposure to pathogens, thereby reducing the frequency of disease outbreaks. An issue with in ovo injecting probiotics is that their is currently no research that describes where these bacteria may colonize within the broiler chick. Using bioluminescent bacteria along with in ovo injection has allowed us in this trial to definitively describe locations within a developing broiler chick bacteria reside and colonize. The results demonstrate that the skin, gastro-intestinal tract, lungs, spleen, and bursa are all locations which the bioluminescent bacteria migrate too. The gastro-intestinal tract is the most important due to the fact it will allow a beneficial gut microflora to flourish before hatch, the lungs, spleen, and bursa are lymphatic sites within the developing embryo and play major roles in immunity. Therefore, in ovo injection of probiotics may also provide a stimulated immune system which can provide earlier protection to the chick when they are exposed to environmental pathogens upon hatch. Overall, this manuscript demonstrates that in ovo injection of probiotic bacteria is a feasible technique for early administration of an antibiotic alternative that could reduce disease outbreaks in the broiler house.

Technical Abstract: In ovo injection of probiotics has been of interest for achieving early health benefits. However, there is limited research demonstrating where bacteria could migrate within the embryo after injection. Thus, the objective of this study was to evaluate bacterial colonization or migration after in ovo injection of broiler embryo with bioluminescent Escherichia coli. Injection using 106 CFU/mL nonpathogenic E. coli were applied to amniotic and air cell regions on d 18 of incubation. On d18, 19, 20 and 21 the amnion, skin, lung, gastrointestinal tract (GIT), bursa, and spleen were collected. On d 21, the GIT was separated into crop, duodenum, jejunum, ileum, and ceca sections. All tissues were visualized using the IVIS to detect bioluminescent E. coli. After that bacterial loads in all tissues were determined. Results indicated that eggs injected into the amnion had significantly high numbers of E. coli cells in all tissues compared to air cell injected and control treatments after 2 h post-injection (P < 0.0001). Also, E. coli penetrated the egg’s inner shell membrane and reached all tissues by d 19. Results indicated that in ovo injection into the amnion was more efficient than air cell injection, yielding a higher bacterial concentration in the evaluated tissues, the ileum and ceca, in particular. Future research using bioluminescent probiotic bacteria may establish sites of preference for different probiotics leading to site-specific application that can maximize their overall impact when in ovo injected.