Research Note: Evaluation of deoxycholic acid for antihistomonal activity.

Deoxycholic acid (DCA) is a naturally occurring secondary bile acid that originates from intestinal bacterial metabolic conversion of cholate, a primary bile acid. Deoxycholic acid was shown to have antihistomonal properties in vitro, leading to our hypothesis that DCA inclusion within the feed might prevent histomoniasis. Selected dietary concentrations of DCA were evaluated for effects on body weight gain (BWG), lesions, and mortality of turkeys challenged with wild-type Histomonas meleagridis (WTH). Treatments consisted of non-challenged control (NC; basal diet), 0.25% DCA diet + challenge, 0.5% DCA diet + challenge, 1% DCA diet + challenge, and a positive-challenged control (PC; basal diet). All groups were fed a basal starter diet until day 7, at which time DCA diets were administered to the respective groups. On day 14, 2 × 10 WTH cells/turkey were intracloacally administered. H. meleagridis-related lesions were evaluated on day 13 post-challenge. Pre-challenge day 0 to 14 BWG was higher (P ≤ 0.05) in the 0.25% DCA group than in the 1% DCA group. There were no significant differences in pre-challenge day 0 to 14 BWG between any of the other groups. No significant differences in mortalities from histomoniasis occurred in the DCA groups as compared to the PC group. No H. meleagridis lesions or mortalities were observed at any time in the NC group. Presence of H. meleagridis-related liver lesions was higher (P ≤ 0.05) in the 0.5% DCA group as compared to the PC group. Using the same controls and experimental timeline, an additional group was included to evaluate a biliogenic diet formulated with 20% whole egg powder to encourage endogenous bile acid production. The biliogenic diet had no statistical impact on pre-challenge day 0 to 14 BWG, but did not reduce H. meleagridis-related mortalities or lesions after the challenge. Taken together, these data suggest that DCA inclusion within the feed at these concentrations and under these experimental conditions does not prevent histomoniasis.