Fig. 1

Experimental layout of the large-scale challenge study. In total, 2024 1-day-old broilers were used in the experiment with 88 control animals and 1936 challenged animals. The challenge was performed on day 16 of the experiment by inoculating 50,000 Eimeria maxima oocysts. Traits were measured at two levels: “global phenotyping” and “detailed phenotyping”. Global phenotyping was performed on all animals and included body weight (BW), plasma coloration (PC), body temperature (BT) and hematocrit (HEMA) levels. Detailed phenotyping was performed on the subset of 176 animals and included lesion score (LS), oocyst count (OC), plasma protein profiles (PPP), and blood composition (BC). Body weight gain (BWG) was calculated using the following formula (BW at day 22-BW at day 15)/BW at day 15. PC is optical density of blood plasma measured for 44 wavelengths (every 5 nm, 380–600 nm) on days 15 and 22. BT was measured at day 23, and HEMA was measured from blood samples obtained on days 16 and 23. BC, PPP, OC and LS were assessed using samples obtained on day 23. Please refer to Hamzic et al. [19] for a detailed description of the trait measurements