###### Abstract  
Lactic-acid-producing bacteria (LAB) are widely used in the poultry industry, and they are positively associated with gut health and growth performance. Despite their wide use in poultry production, LAB appear to be highly variable in their ability to modulate poultry gut health and growth performance. Furthermore, most commercially available LAB probiotics are not host specific; thus, few poultry-specific and even fewer turkey-specific probiotics exist. The objective of this study was to use probiotic screening assays to compare relevant phenotypic differences amongst different species of turkey-derived LAB, in an effort to identify potential probiotics for use in turkey production. Different in vitro assays were used to compare the probiotic potential (phenotype) of each turkey-derived LAB isolate. Twenty-four isolates representing eight different species and five different genera were used for our experiments. These assays included acid tolerance, bile tolerance, and adhesion ability. There was variability in assay performance across many individual strains in every assay performed. Isolates between species and, in some cases, isolates within the same species, differed in their performance between the assays. Some isolates that were identified performed favorably in all the assays in this study. In conclusion, high-performing isolates were identified in this study, which hold potential for influencing turkey health and productivity. probinotic; turkey; lactic acid bacteria +
Footnote †: journal: Applied sciences  
for maximal efficacy. A successful probiotictic needs to survive the transit through the poultry gastrointestinal tract, including the acidic environments of the proventriculars and gizzard [7]. Probiotics must also be able to survive in the presence of bile salts produced by the host [7]. Finally, to avoid the need for continuous administration, a probiotic should be able to persist in the host; thus, they should have strong host cell adhesion and colonization properties [7]. Ideally, optimal probiotictics are also able to inhibit pathogens, either indirectly through nutrient and space acquisition or by producing molecules that directly target pathogens [3]. Lactic acid bacteria (LAB) are some of the most frequently used types of probiotic bacteria in poultry [3]. LAB are widely used because they are natural inhabitants of the animal gastrointestinal tract, and they can withstand the harsh environment of the digestive system [3]. LAB are defined by their ability to produce lactic acid as the major metabolic product of carbohydrate fermentation [8]. They are mostly made up of organisms found in the family _Lactobacillusae_. LAB have been linked to beneficial gut health and development in poultry [6]. Supplementation with LAB has also been linked to increased growth performance in poultry [4; 6; 9; 10; 11]. Many commercially produced LAB probiotics are currently on the market. In fact, poultry probiotics is an industry valued at over $100 million USD worldwide and is forecasted to double in value by 2030 [12]. Despite the popularity of poultry probiotics, scientific evidence regarding their meaningful impacts on poultry health and growth performance seems to be highly varied. One aspect of probiotics often overlooked is host specificity [4]. There is evidence that host specificity may have a positive impact on the success of LAB in a respective host species, including specificity between chicken and turkey hosts [4]. This suggests that coevolution and adaptation of the host and its microbiome may provide a niche advantage for naturally occurring host-specific bacterial strains [4]. Currently, most probiotics marketed for use in poultry are not poultry derived at all. Of those that are poultry sourced, most are derived from chickens. Therefore, there is a need for turkey-sourced probiotic options that have stronger specificity for colonizing the turkey host. This study was performed in an effort to identify turkey-sourced probiotics with potential for use in commercial turkey production.