Efficacy of an attenuated vaccine against avian coccidiosis in combination with feed additives based on organic acids and essential oils on production performance and intestinal lesions in broilers experimentally challenged with necrotic enteritis

Abstract

Several factors predisposing to necrotic enteritis (NE) have been identified, including diet and Eimeria spp. infestations. Coccidiosis vaccines are indicated to decrease the intestinal lesions caused by specific Eimeria species that are a known predisposing factor to NE and, consequently, these vaccines could be a holistic approach to the control of NE disease and an alternative solution to coccidiostats. Besides, feed additives have also gained special attention from the poultry industry as an alternative solution to antibiotics to prevent NE as well as other bacterial enteritis. Then, the combination of vaccination against coccidiosis and the supplementation of the diet with feed additives could be a composite approach to the control of NE problems triggered by Eimeria spp. infestation. The objective of this study was to test the efficacy of an attenuated coccidiosis vaccine (EVANT) in combination with different feed additives to prevent the loss of production performance and intestinal lesions in broilers challenged with NE. Healthy day-old broilers (n = 960) were randomly allocated to 6 groups (8 cages/group). Groups 1-2 were left unvaccinated. Groups 3-6 were vaccinated following the manufacturer's instructions. Chickens were grown using a diet favoring the intestinal proliferation of Clostridium perfringens. Moreover, the diets of groups 4-6 were supplemented with medium chain fatty acids (MCFA), butyric acid or phytogenic feed additives (PFA), respectively. A NE infection model was used to challenge groups 2-6; chickens were orally infected with Eimeria maxima (4,500 oocysts) and then C. perfringens (10⁸ CFU) at 15 and 20 d, respectively. Birds were monitored and productive parameters recorded until 42 d; intestinal lesions were scored. Results showed that coccidiosis vaccination, with or without the addition of feed additives, decreased intestinal lesions associated with NE and improved the performance of the birds. Besides, the addition of MCFA to the diet decreased intestinal lesions associated to NE in vaccinated animals compared to all treatment groups. Moreover, the same additive improved the feed conversion rate. Therefore, vaccination with a live attenuated coccidiosis vaccine together with in-feed inclusion of MCFA might be a solution to reduce NE in broilers raised antimicrobial- and coccidiostat-free.

Keywords: Eimeria; broilers; feed additives; necrotic enteritis; vaccine.