Enzymatically prepared alginate oligosaccharides improve broiler chicken growth performance by modulating the gut microbiota and growth hormone signals

Alginate oligosaccharide (AOS) holds great potential as a novel feed supplement in farm animals. However, the effects of AOS on chicken health and the underlying mechanisms are not fully understood. Here, we cloned and expressed different bacterial alginate lyases in Pichia pastoris GS115 and evaluated the role of the enzymatically prepared AOS in improving chicken health. We found that dietary AOS promoted chicken growth and improved the gut barrier and absorption function. Metagenomic analysis indicated that AOS modulated the chicken gut microbiota structure, function, and microbial interactions and especially promoted the growth of short-chain fatty acid (SCFA)-producing bacteria. Importantly, we demonstrated that AOS can be utilized by Dorea sp. to grow and to produce acetate, which potentially regulates chicken ghrelin and growth-related hormone signals. Overall, for the first time, we established the connections among AOS, chicken gut microbiota/SCFAs, growth hormone signals and chicken growth performance.