Martina Felici 1, Benedetta Tugnoli 1, Dong Xia 2, Andrea Piva 1,3, Virginia Marugan-Hernandez 2 , Ester Grilli 3,4
1 Vetagro S.p.A., Via Porro 2, 42124 Reggio Emilia, Italy;
2 Department of Pathobiology and Population Sciences, Royal Veterinary College, University of London, Hatfield AL9 7TA, UK;
3 DIMEVET, Dipartimento di Scienze Mediche Veterinarie, Università di Bologna, Via Tolara di Sopra 50, Ozzano dell’Emilia, 40064 Bologna, Italy;
4 Vetagro Inc., 17 East Monroe Street Suite #179, Chicago, IL 60603, USA
Poultry coccidiosis is a critical disease and limitations in the current control methods emphasize the need for effective compounds against Eimeria.
This study aimed to examine the effects of salinomycin and a thymol-based botanical blend on cecal health, oocysts output and transcriptomic profiles in broilers challenged with E. tenella.
A total of 200 day-old chicks (Ross 308) were divided in 4 groups (50 birds each): unchallenged (UC) and challenge (CC) controls fed a basal diet and two groups challenged and fed a basal diet added with salinomycin at 60 ppm (SA) or a microencapsulated thymol-based additive at 500 ppm (AP). The challenge was an oral gavage with 10,000 E. tenella oocysts at day 15. At day 2, 5, 6 and 7 post infection (dpi) 10 birds per group were sacrificed for cecal lesion scores and cecal tissue collected for transcriptomic analysis. At 7 dpi, feces were randomly collected (4 points each group) to determine oocysts per gram (OPG) of feces by McMaster method and oocysts integrity (OI) by microscopy using a cell counting chamber (n=4). After 7 days in K-dichromate (2.5%), the sporulation rate (SR) was assessed by counting sporulated oocysts over the total (n=4). Lesion scores were assessed according to Johnson & Reid (1970), averaged from both ceca and analyzed with mixed-effect analysis (n=10). Oocysts data were analyzed with Kruskal-Wallis or 1-way ANOVA based on distribution. Differences were considered significant at P<0.05. For transcriptomics, total RNA was extracted from 5 dpi cecal samples and sequenced on Illumina PE150 platforms. Read counting and differential expression analyses were done with UseGalaxy.eu software. The functional enrichment analysis was done using DAVID Bioinformatics software on KEGG and Gene Ontology pathways. Differentially expressed genes had false discovery rate (FDR)<0.05 and |Log2 FC|>1. Functional enrichment considered pathways with FDR<0.05.
Compared to CC, both SA and AP significantly mitigated cecal lesions starting from 5 dpi (-56%) and reduced OPG counts (-67%), OI (-26%) and SR (-22%) at 7 dpi (P<0.05).
About transcriptomics, the challenge modulated over 4,000 genes compared to UC group, in particular some involved in the cytokine-cytokine receptor interaction and immune response (gga04060 and GO:0006955). Compared to CC, SA modulated 1,663 genes, while AP modulated 684 genes. A total of 377 genes were commonly downregulated by SA and AP, including some cytokines and chemokines (IL6, IFNL3A, IL1R2 and CCL17).
To conclude, the microencapsulated thymol-based feed additive used in this study has the potential to sustain gut health of broilers during E. tenella infection by modulating the immune response to the parasite, similarly to salinomycin.