Evaluation of early feed access and algal extract on growth performance, organ development, gut microbiota and vaccine-induced antibody responses in broiler chickens

•Early feed access and use of algal extract in chicken starter diets were explored.•Growth rate, feed intake and bursa development were improved by early feed access.•No effects of early feed access on gut microbiota or antibody response was detected.•Algal extract supplementation did not affect growth performance or gut health.•Early feed access may be used to improve growth performance in broiler chickens.