Quantifying the effect of coccidiosis on broiler performance and infection outcomes in the presence and absence of control methods
James Taylor, C.L. Walk, Maciej Misiura, J.O.B. Sorbara, Ιlias Giannenas, I. Kyriazakis
Abstract
A systematic review and meta-analysis was conducted to investigate the role of Eimeria species, dose and inoculation time, on performance and infection outcomes of different broiler strains infected for different study durations. The meta-analysis addressed E. acervulina, E. maxima, E. tenella, and mixed species infections, and involved data from 72 peer-reviewed articles, corresponding to 521 treatments performed on 20,756 broilers. A secondary objective was to investigate the effects of synthetic anticoccidials, ionophores, and vaccination against Eimeria on the above outcomes. Performance during infection was scaled (%) to that of the uninfected birds. Infection reduced scaled ADFI and ADG (P < 0.001) and increased feed conversion ratio (FCR; P < 0.05); there was a significant interaction between dose and species on scaled ADFI and ADG, suggesting that different species affected these variables to different extents (P < 0.001). There was a tendency for an interaction between dose and broiler strain on scaled ADFI (P = 0.079), and a significant interaction between these variables on scaled ADG (P < 0.01). A tendency for an interaction between oocyst dose and Eimeria species (P = 0.067) on maximum number of oocysts excreted was observed. Lesion scores were significantly affected by dose, species, and their interaction (P < 0.05), the latter caused by an increase in the lesion scores during E. maxima and E. tenella infections. Control methods significantly affected scaled ADG and FCR (P < 0.05) and there was an interaction between dose and control methods on ADFI (P < 0.001). Synthetic anticoccidial use improved scaled ADG (P < 0.01), whereas ionophores improved FCR compared with untreated birds (P < 0.01). An interaction between dose and control method on scaled ADFI was caused by the higher ADFI of vaccinated compared to untreated birds, as dose increased. There was a significant effect of control methods on lesion scores (P < 0.01). All findings advance our understanding of the factors that influence the impact of coccidiosis and its controls in broilers.