## 4 Discussion  
When comparing turkey-sourced LAB isolates for their ability to grow in acidic conditions, isolates at the species level displayed variability in growth at a pH of 4.0, with _L. vaginalis_ and _P. acidilactici_ showing the highest growth. These results are consistent with other studies performed on isolates of these species derived from host sources other than poultry [21,22]. When the pH was decreased to 3.0, the variability in performance between species decreased, but _P. acidilactici_ had higher growth than most other isolates. Although _P. acidilactici_ has previously been shown to survive in rather acidic conditions, others evaluating this species from non-poultry sources have shown that it was not able to grow well at all when the pH was decreased to 3.0 [21]. This suggests that our turkey-sourced _P. acidilactici_ isolates have properties that allow them to survive in the acidic environment of the poultry digestive tract. In our study, we were able to show that _P. acidilactici_ and _W. paramesenteroides_ had consistently high growth in bile compared to all the other species of LAB. The tolerance of _P. acidilactici_ to higher bile concentrations is consistent with other findings in the literature regarding non-poultry-derived isolates [23]. However, _W. paramesenteroides_ non-poultry-derived isolates had varying ability to grow in bile, with many falling into moderate to poor categories of bile growth performance [24,25]. Some of these grew much poorer in bile compared to _Lactobacillus_ species in the same test, although none were the same species of _Lactobacillus_ used in our study [25]. When comparing these results to our BSH activity assay, we found that although _P. acidilactici_ and _W. paramesenteroides_ had the highest growth in bile, they were all negative for BSH activity. When looking at the results of BSH activity and growth in bile from other species, BSH activity did not seem to affect bile growth performance. In some cases, the presence or absence of BSH activity seemed to have an inverse relationship with increased bile growth. Differences between BSH activity and growth in bile could be due to the use of a single pure bile salt (taurodeoxycholic acid sodium salt), whereas growth in bile involved a mixture of bile salts. _P. acidilactici_ and _W. paramesenteroides_ are potentially able to deconjugate other forms of bile salts found in the bile salt mixture. Other possibilities could be that _P. acidilactici_ and _W. paramesenteroides_ have other mechanisms to survive and grow in bile or have overall increased fitness. When investigating the NCBI gene database, bile salt hydrolase genes have currently been identified in other _Pediococcus_ and _Weissella_ species, but not in the species evaluated in this study [26]. Even though BSH activity is a common probiotic screen method, our results suggest that a more thorough phenotypic evaluation is necessary when assessing an isolate's ability to survive in bile. When comparing the ability of different LAB species to adhere to avian intestinal cells, no significant variation was observed. There was some within-species variability found within this assay, especially in the _W. paramesenteroides_ species. Varied adherence ability in _W. paramesenteroides_ isolates is consistent with another study investigating mucin adhesion [27]. This assay can help to inform which specific isolates should be avoided due to potentially low colonization ability when selecting probiotic candidates. These phenotypic assays can be helpful in narrowing down a large collection of probiotic candidates based on probiotic relevant screenings. However, a limitation of this approach is that it is unclear whether such in vitro differences translate to positive effects in the bird. Bird performance studies are needed to better evaluate and understand the performance differences between different turkey-sourced LAB. Since the isolates of _P.