Abstract Soybean is a key plant-protein source often included in poultry diets for its nearly complete amino acid profile. Outside of protein, soybeans contain a multitude of bioactive compounds that have garnered attention for their potential immunomodulatory effects. Soy saponins are one such compound that may have beneficial anti-inflammatory, antioxidative, and antiparasitic properties. In this study, 810 male Ross 308 chicks at 2-d post-hatch were allotted to 1 of 9 treatment groups with 10 birds in 10 replicate cages for treatments 1-6 and 7 birds in 10 replicates for treatments 7-9. This 28-d feeding study was conducted in a 3 × 3 factorial arrangement with factors including: 1) saponin supplementation (3 levels; no supplementation, soy saponin supplementation at 250 mg/kg active soy saponins, or yucca-derived saponin supplementation at 250 mg/kg commercial yucca saponin product) and 2) challenge status (3 levels; unchallenged, lipopolysaccharide (LPS) challenged, or Eimeria coccidiosis vaccine challenged). After a 15-d acclimation period and 24-h feed withdrawal, birds in Eimeria-challenged groups (treatments 7-9) were orally gavaged with a commercial coccidiosis vaccine at 5× the recommended dose while control group birds (treatments 1-3) received a sham gavage. Cloacal temperatures, blood, and intestinal tissue samples were collected at peak infection 6 d post-inoculation (DPI) and at study termination (13 DPI). On study d 22, birds in LPS-challenged groups (treatments 4-6) received an intraperitoneal injection of E. coli O127:B8 LPS at 2 mg/kg body weight (BW) while control birds received a sham injection. Cloacal temperatures and blood were collected at 0-, 2-, and 4-h post-injection while intestinal tissue samples were only collected at 0- and 2-h. All data were analyzed by ANOVA using the MIXED procedure of SAS. Cloacal temperatures were not affected (P 0.05) by treatment at any of study time-points. Coccidiosis vaccine challenge status was confirmed via oocyst counts, but no differences (P 0.05) were observed for oocyst excretion between infected treatments. Eimeria-challenged birds had reduced (P 0.05) feed intake (FI) and BW gain (BWG) during the peak infection period (d 14-21), resulting in increased (P 0.05) feed conversion ratios (FCR) compared with the non-challenged control treatment. During this period, both soy and yucca saponin supplementation improved (P 0.05) FCR in Eimeria-challenged birds compared with challenged birds on a control diet. LPS challenge had variable effects on FI and BWG post-challenge (d 21-28) but no significant differences (P 0.05) on FCR. Overall, saponin supplementation elicited the most evident benefits in Eimeria-infected birds, improving their FCR during peak infection. Whether this can be explained by their purported anti-inflammatory and antioxidative properties remains to be seen.
White et al. (Wed,) studied this question.