Abstract
An experiment was conducted to quantify the timing and magnitude of the effects of coccidiosis vaccination on the growth performance, apparent ileal digestibility (AID) of nutrients and energy, intestinal morphology, and plasma carotenoids and nitric oxide in broilers. Treatment groups consisted of 3 coccidiosis control methods [unvaccinated, unmedicated (NC), in-feed chemical coccidiostat (PC), and live oocyst vaccination (VAC) at day of hatch] administered to male Cobb broilers reared in floor pens. Body weight gain (BWG), feed intake (FI), and feed conversion ratio (FCR) were determined at 12, 16, 20, 28, and 36 d. Blood and ileal digesta were collected from birds in 10 replicate pens of each treatment at 12, 16, 20, and 36 d to evaluate plasma carotenoid and nitric oxide concentrations and determine nutrient AID and IDE. Jejunal samples were taken at 12, 20, and 36 d for morphological measurements. Oocyst shedding in VAC birds was confirmed by increased oocyst counts and decreased carotenoid concentrations (P < 0.05) when compared with PC birds, with no differences (P > 0.05) in nitric oxide concentrations. At 20 d, BWG and FI were lowest (P < 0.05) in VAC birds, intermediate in NC birds, and highest in PC birds, with no differences in FCR (P > 0.05). By 28 and 36 d, FCR was higher (P < 0.05) for VAC and NC birds but BWG and FI of VAC birds were similar (P > 0.05) to PC birds. At d 12, IDE and AID of nitrogen and ether extract were lower (P < 0.05) in VAC birds than PC birds. At d 16, AID of nitrogen was similar (P > 0.05) between PC and VAC birds, whereas AID of ether extract remained lower in VAC birds than PC birds. No differences in AID of nutrients or IDE were observed (P > 0.05) between VAC and PC birds at 20 or 36 d. No differences (P > 0.05) in jejunal morphology were observed at any time point. Overall, VAC elicited a transient reduction in AID and IDE, particularly for lipids, that diminished by d 20.
Highlights
Coccidiosis, an intestinal parasitic disease caused by protozoa of the genus Eimeria, remains one of the most prevalent diseases in commercial poultry production
At 12 and 16 d post hatch, oocysts per gram (OPG) counts from VAC birds were significantly (P < 0.05) higher than those of NC and PC treatments
Litter oocyst counts and plasma carotenoids indicated that in-feed diclazuril administration prevented coccidial infection in PC birds, whereas increased oocyst shedding and decreased plasma carotenoid concentrations reflected cycling of vaccinal oocysts in VAC broilers
Summary
Coccidiosis, an intestinal parasitic disease caused by protozoa of the genus Eimeria, remains one of the most prevalent diseases in commercial poultry production. Such systems do currently permit the use of chemical anticoccidial drugs, there is a limited number of these compounds and their overuse can quickly lead to emergence of drug resistant Eimeria strains [1, 2]. This resistance has increased reliance on live oocyst coccidiosis vaccination, which can induce immunity and reintroduce drug-sensitive strains into the rearing facility, as an important control strategy for coccidiosis [3]. Impaired feed efficiency during vaccine cycling is presumably due in part to nutrient malabsorption associated with intestinal damage and inflammation associated with the sub-clinical, vaccine-induced infection [5,6,7]
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