SUMMARY.

This study was conducted to investigate the effects of replacing in-feed antibiotics with synergistic organic acids on growth performance, health, carcass, and immune and oxidative statuses of broiler chickens under Clostridium perfringens (CP) type A challenge. Two organic acid products were tested: organic acid 1 (OA1), consisting of butyrate, medium-chain fatty acids, organic acids, and phenolics; and organic acid 2 (OA2), consisting of buffered short-chain fatty acids. Six hundred 1-day-old male Arbor Acres broiler chicks were randomly assigned to one of five treatments: Control 1, basal diet, nonchallenged birds; Control 2, basal diet, with CP challenge; antimicrobial growth promoters (AGP), basal diet supplemented with Aureomycin (chlortetracycline), with CP challenge; OA1, basal diet supplemented with OA1, with CP challenge; and OA1OA2, basal diet supplemented with OA1 and OA2, with CP challenge. Each treatment had eight replicate pens of 15 birds. The experiments lasted for 29 days. The disease challenge was performed on days 15–17, with an oral gavage of 0.5 mL of CP culture (2.0 × 108 colony-forming units [CFU]/mL) for each bird. Body weights (BWs), intestinal lesion scores, immune organ indices, and serum malondialdehyde (MDA) concentrations were measured on days 19, 22, and 29, respectively, in three birds per pen. Carcass characteristics were determined on day 29. No treatment-related differences in mortality were noted before (P = 0.28) or after (P = 0.64) challenge or over the whole study period (days 0–28; P = 0.66). On day 19, the BW of Control 2 was lower than other treatments (P < 0.0001). On day 22, AGP, OA1, and OA1OA2 had higher BW than Control 2 (P = 0.001). The breast muscle yield of OA1 and OA1OA2 was higher than AGP (P < 0.05). The abdominal fat yield of OA1OA2 was lower than AGP and Control 2 (P < 0.05). On day 22, the birds fed OA1OA2 showed lower intestinal lesion scores than OA1 (P < 0.05). No treatment-related differences in immune organ (spleen, thymus, and bursa) indices were noted (P > 0.05). On day 29, the MDA concentration of OA1 and OA1OA2 was lower than those of Control 1 and AGP (P < 0.05). In conclusion, the addition of organic acids may protect broiler chickens from severe intestinal lesions and oxidative stress and may help reduce abdominal fat mass deposition. There is potential for organic acid–based products as alternatives for AGP in preventing necrotic enteritis in broilers.

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