POSITIVE EFFECT OF QUILLAJA SAPONARIA AND YUCCA SCHIDIGERA BLEND IN COCCIDIOSIS CHALLENGE MODEL AND POTENTIAL MODE OF ACTION V. STANEV 1 , B. MAERTENS 2 , L. GOMEZ 3 , S. BONASPETTI 4 and G. INWOOD 5 Summary Numerous scientific publications and commercial use data indicate the positive effect of Quillaja saponaria and Yucca schidigera combination product (QY) on broiler performance when exposed to an Eimeria spp. challenge. This has created the perception of an anticoccidial effect of such a combination. To assess this hypothetical effect and identify the specific mode of action of QY in coccidia challenged broilers a series of in vivo and in vitro trials have been carried out. In the in vitro study QY did not exhibit a direct anticoccidial effect, assessed by the reduction of sporozoite viability during in vitro incubation at physiologically relevant concentrations in comparison to registered anticoccidial products such as salinomycin and toltrazuril. However, QY demonstrated numerous beneficial effects when used alone or in combination with either a coccidiosis vaccine or an in-feed anticoccidial when birds were exposed to coccidiosis challenge. QY had a positive effect on performance prior to the challenge (d 0-14) on oocyst shedding expressed as oocyst per gram feces (OPG) and performance during the recovery phase (d 28-35), but not during the acute phase (d 14-28). This suggests that the positive effect of QY under coccidiosis challenge is due to improved immunity development, reduced inflammation and tissue damage and faster recovery, rather than direct anticoccidial effect. I. INTRODUCTION Natural triterpenoid saponins from Quillaja saponaria such as QS 21, QS 17, QS 18 and QS7 are known to support specific immune response towards different pathogens (Lacaille- Dubois, 2019; Marciani et al., 2000). As well, natural polyphenols from both Q. saponaria and Yucca schidigera such as piscidic acid, vanillic acid, ferulic acid, p-coumaric acid, resveratrol and yuccaols are known to have antioxidant and anti-inflammatory effects (Maier et al., 2015; Piacente et al., 2005). Furthermore, numerous scientific publications (Bafundo et al., 2020, Bafundo et al., 2022) and commercial field experience indicate positive effects of the Q. saponaria and Y. schidigera combination product (QY) (Magni-Phi ® ), containing a minimum of 3.5% triterpenoid (Quillaja) saponins and typically 0.8-1.0% of total polyphenols expressed as gallic acid equivalent on broiler performance when exposed to an Eimeria spp. challenge. This has created a perception of an anticoccidial effect of this combination. The current study aims to assess this effect and helps to identify the specific mode of action of QY in coccidia challenged broilers. II. METHOD a) In vivo study. A total of 1 848 day old male Ross 308 broilers were allocated into 7 treatments: T1 - uninfected untreated control (UUC); T2 - infected untreated control (IUC); and five infected treatments: T3 - supplemented with QY; T4 - supplemented with in-feed anticoccidial: narasin+nicarbazin (100 ppm 0-21 d), followed by salinomycin (60 ppm 22-35d) 1 Phibro Animal Health SA, 1300 Wavre, Belgium; vasil.stanev@pahc.com 2 Poulpharm BVBA, 8870 Izegem, Belgium; 3 Phibro Animal Health Corporation, Teaneck, NJ 07666, United States; 4 Phibro Animal Health SA, Campinas, SP 13025-170, Brazil; 5 Phibro Animal Health PTY, Bella Vista, NSW, 2153, Australia; Aust. Poult. Science Symp. 2024 ...35 237