The use of a live non-attenuated coccidiosis vaccine modifies Eimeria spp. excretion in commercial antibiotic-free broiler chicken flocks compared to conventional shuttle anticoccidial programs.

The objectives were to compare the effects of an antibiotic-free (ABF) program in commercial broiler chicken flocks using a live non-attenuated coccidiosis vaccine on fecal Eimeria spp. excretion and growth performances with those of conventionally raised commercial broiler chicken flocks. Fecal samples were collected every 3 d from 7 d of age to slaughter in 44 flocks of 7 participating farms for oocyst counts by the McMaster method. A live non-attenuated anticoccidial vaccine was administered by spray cabinet at the hatchery in ABF flocks only. Shuttle programs in conventional flocks consisted of in-feed chemical anticoccidials from 0 to 20 d of age, followed by polyether ionophores until slaughter. In-feed antibiotic growth promoters were included from the starter to finisher diets in conventional flocks only. Age of the flock at the oocyst excretion peak (AGE_PEAK) and the number of oocysts at that excretion peak (OPG_PEAK) were recorded. There was a significant difference of 2.7 d (P = 0.0001) for the AGE_PEAK, from 26.4 d in the conventional treatment to 23.7 d in the ABF program. There was no significant difference for the OPG_PEAK between the 2 treatments (P = 0.626). There was a significant decrease of 2.28 g in the average daily gain (P = 0.004) and increase of 0.08 for the feed conversion ratio (P < 0.0001) in the ABF program compared to the conventional program. There were no significant differences for body weights at slaughter (P = 0.0563), livability (P = 0.2694), and condemnations (P = 0.6775). From this study, it can be concluded that an ABF program using a live non-attenuated vaccine will show an earlier oocyst excretion peak compared to a shuttle program, but no significant effect was observed on the total number of oocysts at that excretion peak between the 2 programs.