Method: Protocol for in-ovo stimulation with selected pro-/prophy-biotics to mitigate Campylobacter jejuni in broiler chickens

Broiler chickens are a natural reservoir for Campylobacter which is largely responsible for the highest reported zoonotic infection within the Europe, Campylobacteriosis. However, despite extensive scientific investment, the broiler industry is still in need of effective intervention strategies to control this pathogen in broiler production. In-ovo modulation has been studied extensively as a method to positively modulate the gastrointestinal microflora in broiler chickens. However, the efficacy of an in-ovo method against Campylobacter has not been studied to date to the best of our knowledge. Therefore, the current study was conducted to validate the efficacy of a protocol for in-ovo stimulation of ROS308 broiler chicken eggs with Leuconostoc mesenteroides B/00288 strain alone (probiotic) and in combination with garlic aqueous extract (prophybiotic) in reducing the abundance of Campylobacter jejuni in ceca. On 12th day of incubation, the selected doses of the probiotic and prophybiotic were injected into the air cell of the eggs as treatments. Two control groups (Negative control: without injections and positive control injected with physiological saline) were also included in the experiment. The impact of the protocol on hatch parameters (hatchability, chick length, chick weight and Pasgar score), BWs and feed conversion ratio was recorded. When the chickens were 21 days old, an infection challenge with Campylobacter jejuni was performed. A quantitative PCR method was used to quantify the Campylobacter relative abundance in faeces (one week postinfection) and in the cecal content (at the age of 35 days). The probiotic treatment significantly (P-value = 0.0020) reduced the Campylobacter jejuni numbers in the ceca while the prophybiotic treatment resulted in a statistical tendency (P-value = 0.0691) in reducing the abundance of Campylobacter jejuni in ceca. Both treatments had no adverse effects on the hatch or production parameters studied. In conclusion, in-ovo stimulation with the probiotic Leuconostoc mesenteroides demonstrated potential in reducing Campylobacter jejuni colonisation in the ceca of ROSS308 broiler chickens infected at 3 weeks of age.