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The efficacy of Actigen® (AG) as a replacement for zinc bacitracin (ZB) and salinomycin (SM) was investigated using necrotic enteritis (NE) challenge feeding study model. 480 d old male Ross 308 chicks were assigned to 48 floor pens (75 x 60 cm) in 2 rooms. Treatments were arranged in a 2 x 4 factorial design: challenge, - or +; feed additive, control (none), ZB 100/50 ppm; AG 800/400/200 ppm and SM 60 ppm in S, G, and F respectively. Wheat, sorghum, SBM, MBM, canola diets were formulated according to Ross 308 nutrient specifications. Birds in one room were gavaged on day 9 with 1 ml saline containing sporulated oocysts of vaccine strain 'E. maxima' (5000), 'E. acervulina' (2500) and 'E. brunetti' (2500) following gavage on days 14 and 15 with 1 ml thioglycollate broth (TB) containing 108 CFU of 'C. perfringens' (strain EHE-NE18, CSIRO). Unchallenged birds were dosed with saline or TB. Results on d 35 showed lower livability (LV), weight gain (WG) and feed intake (FI) in challenged vs unchallenged birds (P<.05). ZB, Actigen and SM increased LV, WG and FI on d 35 (P<.05). Challenge X additive interactions were observed for LV, WG and FI on d 35 (P<.01). In the - vs + challenge groups, LV was 92 vs 52, 97 vs 90, 92 vs 82 and 93 vs 93% while WG was 2541 vs 2105, 2597 vs 2474, 2699 vs 2561 and 2575 vs 2704g for control, ZB, Actigen and SM respectively. Control birds had greater incidence of NE lesions when challenged (P<.01). None of the additives completely protected birds from NE or cocci lesions. Actigen was as effective as ZB and SM in preventing performance decline from coccidiosis. This study indicates that yeast based Actigen® has promise as a tool for controlling necrotic enteritis. |
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