Microbiocenosis of the chicken ceca: impact of in ovo delivered bioactive substances, heat stress, and antibiotic growth promoters

The chicken gut microbiota plays important roles in host physiology and well-being. It can be impacted by several management and environmental factors like the use of antibiotic growth promoters (AGP) and heat stress (HS). Probiotics, essential oils (EO), and vitamins (such as folic acid) are bioactive substances that could potentially modulate the gut microbiota and promote its resilience to stressful environmental factors, especially when supplied as early as during embryonic development. This study evaluated the gut microbiota modulating potential of in ovo delivered probiotics, folic acid (FA), and in ovo + in-water delivered EO in broiler chickens, as compared to an in-feed AGP, under an HS challenge. Results from this study indicate that HS, AGP, and in ovo + in-water EO treatments modified chicken ceca bacterial populations and suggest that the microbiota-mediated role of AGP in growth promotion is related to improved biosynthesis of essential nutrients (amino acids and vitamins especially) and utilization of carbon sources derived from host diet and microbiome.