Trends involved in bacterial transfer for day-of hatch chick microbiome

Bacteria from breeders and the hatchery are predicted to be the primary sources of bacterial inoculum for day-ofhatch chicks. Breeders donate fecal bacteria as part of the normal laying process, while handling and transportation further adds bacteria onto the egg shell. As a model, E. coli has been used to study bacterial transfer from breeders to hatchery and chicks. From these studies, it was determined that E. coli could be successfully isolated on the egg shell and survive the hatching process. Chicks then maintained the initial E. coli strains up through the last day of monitoring at d 8. What is not yet understood are the larger dynamics of bacterial populations that are inoculated into chicks at day of hatch. To study bacterial transfer in production systems, a post-hoc study of bacterial populations was elucidated through 16s sequencing and monitored through linear breeder, hatchery surfaces, and day-of-hatch chicks. Bacterial populations were aligned to the areas sampled and then modeled for transfer from area to area. Bacteria deposited onto the egg shell from the breeder continued to be a primary source of bacteria that was maintained from collection through the hatching process. Day-of-chicks demonstrated significant bacterial populations related to density of bacteria on the egg shell. Much of day-of-chick gut resident bacteria was comprised of 4 separate bacterial species, while several minor bacteria were identified between 2 and 0.1% relative abundance to total reads. Together, although several bacterial species are co-localized on surfaces and are present to day-of-hatch chicks, density of bacteria appears to be key in bacterial transfer. However, it cannot be ruled out how acclamation to gut environment of adaptation of transfer may also play a role. After day-of-hatch, repeated exposure to bacteria, adaptation to the gut environment, and nutrition may further shape bacterial communities and development.

Key Words: breeders, microbiome, hatchery, transfer.

Presented at the Symposium on Gut Health in Production of Food Animals 2019 in St. Louis, USA.