The efficacy and economic benefits of Paracox®, alive attenuated anticoccidial vaccine, in commercial trials with standard broiler chickens in the United Kingdom

Abstract The first large-scale broiler trials under modern commercial conditions of Paracox ® , a live attenuated anticoccidial vaccine administered in the drinking-water, arereported from the United Kingdom. The vaccine, comprising all seven of the species of Eimeria that parasitise the domesticated fowl, was compared with anticoccidial drug shuttles (halofuginone then salinomycin, or nicarbazin then monensin) in nine trials comprising over 936 000 chickens, all of which also received the digestive enhancer virginiamycin. No clinical diseaseswere diagnosed in vaccinated birds in any of the trials. Necrotic enteritis occurred in themedicated controls (anticoccidial drug shuttles) of 2/9 trials and coccidiosis occurredconcurrently with one of these outbreaks. Using additional criteria that particularly reflectedeconomic benefits, the vaccine performed overall at least as well as the drug shuttles. The crucialresults for vaccinated and medicated birds were: feeding costs (pence per kg liveweight of birdsthat were processed), 33.9 pence (vaccinated) and 33.7 pence (medicated) ( P =0.549);feed conversion ratios, 2.01 (vaccinated) and 1.96 (medicated) ( P =0.025); coefficientof variation in mean bird weight before processing, 9.3% (vaccinated) and 9.0% (medicated) ( P =0.300); birds found dead, 3.0% (vaccinated) and 3.8% (medicated) ( P P =0.483); birdsrejected during processing, 1.1% (vaccinated) and 1.2% (medicated) ( P =0.271). Inaddition, the mean total water consumptions per chick were 7.82 L (vaccinated) and 7.76 L (medicated) ( P =0.611), whilst the mean percentages of dry matter in the litter were76.2% (vaccinated) and 75.2% (medicated) ( P =0.195). Accumulation of oocysts in thelitter of chicks vaccinated at 5 days of age peaked at 21 and 35 days, compared with medicatedcontrols which showed a single higher peak at 35 days. Hence, the use of Paracox ® vaccine may control clinical coccidiosis in broilers and also achieve performances at least equal toanticoccidial drugs, particularly where drug resistance might result in failure to control disease.