Control of necrotic enteritis (NE) in broilers is a challenge, especially when raising antibiotic-free flocks. NE is well controlled with antibiotic feed additives, but increased awareness to antimicrobial resistance has seen the development of commercial alternatives. Our objectives were to test the efficacy of some alternatives to control or reduce mortality during a NE experimental infection. Four sets of experiments were done, each involving 4 repetitions of 6 treatments. These consisted in the administration of 1) inorganic or organic water acidifiers at 2 pHs, 2) and 3) commercial essential oils, organic acids, yeast or bacitracin added to the diet and 4) a combination of organic acid in water and essential oils in feed. The infection model included increased wheat in the diet, vaccination against coccidiosis and four consecutive oral inoculations of 3 field Clostridium perfringens strains.
None of the treatments fully prevented the occurrence of NE. Mortality and typical lesions were observed in all groups but uninfected ones. There was no significant difference in mortality between treatments for infected groups. While mortality was inferior to 6% in all trials, it was up to 15% in trial 2, an increase later explained by a higher than usual first inoculation dose. Lack of bacitracin efficacy to prevent NE in trials 2 and 3 was later shown to be likely caused by bacitracin resistance in one of the inoculated Clostridium perfringens strains. This particular strain appears to take over the two others as shown by PFGE analysis. There were significant lower gross and histopathological lesion scorings for some treatments, mostly essential oils based products. Gut contents of selected treatments were pyrosequenced to verify impact on microbial community. Overall our infection model is repeatable but another antibiotic will be required as control when comparing alternatives to antimicrobials.