Comparing performance and resistance of two broilers breeds challenged by Eimeria acervulina.

The proposal on the ban of anticoccidials drugs from poultry feed highlights the importance of broiler breeders resistance to Eimeria as a criteria for animal genetic selection. The aim of this study was to compare the resistance between two commercial broiler breeds to Eimeria acervulina. Eight hundred male chicks from two commercial breeds (400 animals each) were housed from 1-42 days of age and randomly divided into 4 treatments with 8 replicates of 25 birds each. Following a factorial design, the treatments were AU, BU (breed A and B, unchallenged), AC and BC (breed A and B, challenged at 14 days of age by gavage with 1 × 10 oocysts of a field strain of E. acervulina). From 1-42 days, feed intake, body weight gain (BWG), feed conversion ratio (FCR), feed efficiency and mean weight (MW) were weekly measured. For the clinical evaluation, feces were sampled from 18 to 24 days for the counting of excreted oocysts and twenty birds per treatment were euthanized at 20 days of age for the scoring of macroscopic lesions in the gut. The breeds did not show statistical differences in performance after the Eimeria challenge in all phases. Breed A presented a higher increase in FCR from 21 to 45 days in comparison to the breed B, which presented a deeper reduction in FI, BWG and MW at all periods post-infection when compared to the breed A. Despite of the challenge, breed A presented better performance indexes (P < 0.05) up to the 28 days of age in comparison to the breed B, however, no significant difference in performance was detected between the breeds at the final age of 42 days. Regardless of the breed, the challenged birds presented significant worsens in all performance parameters from 14 to 42 days of age. The breed B presented a higher (P < 0.05) fecal count of oocysts from 19 to 21 days and higher (P < 0.05) score of macroscopic lesions in the gut at 21 days in comparison to the breed A. The clinical evaluation pointed out a lower resistance of the breed B to the E. acervulina challenge, which could result in significant impacts on the performance in field production conditions.