SUMMARY. Restrictions on the use of antibiotics in poultry production have increased interest in non-antibiotic alternatives to control necrotic enteritis (NE). Volatile fatty acids, and in particular butyric acid preparations, have shown potential as aids in controlling NE. Valeric acid compounds may be a new additional alternative. This series of 3 trials compared the effects of tributyrin, monovalerin, an organic acid mixture, and bacitracin in a necrotic enteritis challenge model consisting of challenge with coccidiosis followed by Clostridium perfringens. Trial 1 was a pen trial comparing tributyrin at 0.5 Kg per metric ton continuously in the feed, a proprietary organic acid blend at 1 Kg per 1000 L as a metaphylactic treatment in the water, and bacitracin in the feed at 55 g per metric ton. Tributyrin and the organic acid mixture were at least as effective as bacitracin in controlling the growth- and efficiency-suppressing effects of the NE challenge, and the organic acid mixture reduced NE lesion scores. None of the treatments reduced mortality. Trial 2 was a battery study comparing monovalerin at 1.5 Kg per metric ton and bacitracin in the feed. Both interventions provided significant control of both clinical and subclinical NE, with bacitracin being slightly superior to monovalerin. Trial 3 was a pen trial comparing monovalerin at 1 Kg or 1.5 Kg per metric ton continuously, or 0.5 Kg per metric ton from 0 to 14 days and 0.25 Kg per metric ton from 14 to 42 days (variable dose), to tributyrin at the same variable dose schedule. The higher dose of monovalerin appeared to suppress feed intake and weight gain pre-challenge, but also produced the lowest NE mortality and the lowest total mortality of the challenged groups. All of the treatments except the variable dose monovalerin treatment demonstrated reductions in NE lesion scores compared to the positive challenge control group, but did not control mortality and had less effects on the performance impacts of subclinical NE. Results of these studies indicate that the organic acid products Monovalerin and tributyrin may be useful adjuncts to reduce NE in antibiotic-free broiler production.

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