ObjectiveThe use of probiotics as an alternative to antibiotics in animal feed has received considerable attention in recent decades. Lactic acid bacteria (LAB) have remarkable functional properties promoting host health and are major microorganisms for probiotic purposes. The aim of this study was to characterize LAB strains of the chicken digestive tract and to determine their functional properties for further use as potential probiotics in poultry.MethodsA total of 2,000 colonies were isolated from the ileum and cecal contents of the chickens based on their phenotypic profiles and followed by a preliminary detection for acid and bile tolerance. The selected 200 LAB isolates with exhibited well-tolerance in acid and bile conditions were then identified by sequencing the 16S rDNA gene, followed by acid and bile tolerance, antimicrobial activity, adhesion to epithelial cells and additional characteristics on the removal of cholesterol. Then, the two probiotic strains (L. ingluvieiandL. salivarious) which showed the greatest advantagein vitrotesting were selected to assess their efficacy in broiler chickens.ResultsIt was found that 200 LAB isolates that complied with all measurement criteria belonged to five strains, includingL. acidophilus(63 colonies),L. ingluviei(2 colonies),L. reuteri(58 colonies),L. salivarius(72 colonies), andL. saerimneri(5 colonies). We found that theL. ingluvieiandL. salivariuscan increase the population of LAB andBifidobacteriumspp. while reducingEnterobacteriaspp. andEscherichia coliin the cecal content of chickens. Additionally, increased concentrations of valeric acid and short chain fatty acids were also observed.ConclusionThis study indicates that all fiveLactobacillusstrains isolated from gut contents of chickens are safe and possess probiotic properties, especiallyL. ingluvieiandL. salivarius. Future studies should evaluate the potential for growth improvement in broilers.