Graded Eimeria challenge linearly regulated growth performance, dynamic change of gastrointestinal permeability, apparent ileal digestibility, intestinal morphology, and tight junctions of broiler chickens

Abstract

This study was conducted to evaluate graded Eimeria challenge on growth performance, apparent ileal digestibility, gastrointestinal permeability, intestinal morphology, gene expression of tight junction protein, and intestinal lesion scores in broiler chickens. There were 5 groups in this study, including a control and 4 different Eimeria treatment doses. A mixed Eimeria spp. solution with 50,000  Eimeria maxima, 50,000  Eimeria tenella, and 250,000  Eimeria acervulina per milliliter was prepared for the high-dose challenge treatment. The 2-fold serial dilution was used to make the medium-high (25,000  E. maxima; 25,000  E. tenella; 125,000  E. acervulina), the medium-low (12,500  E. maxima; 12,500  E. tenella; 62,500  E. acervulina), and the low challenge dose (6,250  E. maxima; 6,250  E. tenella; 31,250  E. acervulina). A total of three hundred sixty 13-day-old male broiler chickens were randomly allocated into 5 treatments with 6 replicated cages. Growth performance was calculated from 0 to 6 D postinfection (DPI). Intestine lesion was scored on 6 DPI. Gastrointestinal permeability was measured on 3, 5, 6, 7, and 9 DPI. The results indicated significant linear reduction in growth performance, intestinal villi height, and ileal nutrient digestibility in response to the increase of Eimeria challenge dose. Furthermore, gene expression of tight junction protein was linearly upregulated by the increasing challenge doses. Significant linear increases of gastrointestinal permeability were found on 5, 6, and 7 DPI ( P < 0.01). On 9 DPI, the gastrointestinal permeability was recovered back to normal level in the challenge groups. In conclusion, the higher Eimeria doses birds received, the more severe intestine damage was observed in several gastrointestinal health parameters. The medium-low or medium-high levels of mixed Eimeria oocysts is suggested as an optimum Eimeria-challenge dose to establish a subclinical challenge model for future studies evaluating nutritional strategies. Moreover, it is recommended to measure gastrointestinal permeability on 5 DPI with higher oocysts doses and 6 DPI when using the lower oocysts doses.