Topical Application of Adult Caecal Contents to Eggs Transplants Spore-Forming Microbiota but Not Other Members of the Microbiota to Chicks.

The intestinal microbiota plays an essential role in the metabolism and immune competence of chickens from the first day of hatch. In modern production systems, chicks are isolated from adult chickens, instead hatching in a clean environment. As a result, chicks are colonised by environmental bacteria including potential pathogens. There is a need to investigate methods by which chicks can be exposed to the a more appropriate microbial community at hatch. Such methods must be easy to apply in a hatchery and produce consistent results. The development of the intestinal microbiota of chicks hatched from eggs sprayed with dilute adult caecal content during incubation was observed at 0, 3, 7 and 14 days post hatch (d.p.h) across two experiments. High-throughput Illumina sequencing was performed for the V4 hypervariable region of the 16S rRNA gene. A topical treatment of dilute adult caecal content was sufficient to transplant spore-forming bacteria such as Lachnospiraceae and Ruminococcaceae. However, this treatment was not able to transplant other taxa that are considered to be core elements of the chicken caecal microbiota such as Bacteroidaceae, Lactobacillaceae, Bifidobacteriaceae and Burkholderiaceae. The topical treatment significantly altered the microbiota of chicks immediately post-hatch and accelerated the normal development of the microbiota with earlier colonisation by Ruminococcaceae in the caecum and Candidatus Arthromitus in the ileum. The effect of the treatment on caecal microbiota was maximal at 3 d.p.h but diminished over time. IMPORTANCE Over the last 60 years poultry production has intensified in response to increased demand for meat. In modern systems, chicks hatch without contacting chickens and their gut bacteria. Consequently, they are colonised by environmental bacteria that may cause disease. The normal bacteria that live in the gut, or intestinal microbiota, play an important role in the development of the immune system. Therefore, it9s essential to find easy ways to expose chicks to the more appropriate bacteria at hatch. This experiment investigated whether spraying eggs with adult caecal contents was sufficient to transfer an adult microbiota to chicks. Our findings show that spore-forming bacteria were transplanted but other members of the microbiota were not. In this respect, the spray application was partially successful but the timing of the spray needs to be modified to ensure that more bacteria are transferred.