cjs-202308-0002 ArticleInAPeriodical 2023 Czech Journal of Animal Science 68 8 346-355 Abdulrazaq M'SadeqShawkat Ameliorative effect of yeast cell walls on broiler chickens' performance and gut health under coccidiosis challenge This study was conducted to evaluate the efficacy of yeast cell wall parts (YCW) in reducing the severity of coccidiosis in broiler chickens. One-day-old Ross 308 chicks (n = 320) were randomly allocated to 32 floor pens in two rooms with a 2 × 4 factorial arrangement of treatments. Factors were (1) challenge: negative or positive by room, (2) feed additive: control (none), anticoccidial (salinomycin at 60 mg/kg), YCW 0.1% or 0.2%. On day 8, none-challenged room was inoculated with saline, and challenged room was inoculated with 5 000 Eimeria tenella oocysts. Performance results showed that in challenged birds, feed conversion ratio (FCR) and weight gain (WG) were poorer than in unchallenged birds on day 24 and 35. Birds given anticoccidial and YCW had improved FCR and WG (P = 0.01) over the control group. Challenge and additive interactions were observed on day 24 and day 35 for FCR and WG (P = 0.01) and for feed intake on day 24 (P = 0.01). Challenged birds fed YCW on days 24 and 35 had higher WG and better FCR compared with both challenged and non-challenged controls and anticoccidial treatment. Coccidial challenge increased crypt depth (CD), villous tip and base width, and villous surface area and decreased villous height to crypt depth ratio (VH : CD) and villous height (VH). Birds fed YCW exhibited significantly decreased CD, villous tip width, villous base width, villous surface area and increased VH, VH : CD in comparison to the control group. Challenged birds fed YCW had significantly lower bursa of Fabricius follicle length compared to birds fed the control diet. Challenged birds had significantly increased serum alanine transaminase (ALT) and aspartate aminotransferase (AST) concentrations than non-challenged birds. In conclusion, these results demonstrated that the yeast cell wall has the ability to control coccidiosis.