Efficacy of Synergistic Blend of Feed Additives on Growth Performance, Gut Health and Bird Welfare in Broilers Challenged with Necrotic Enteritis

A feeding study was conducted to examine the efficacy of a synergistic blend of feed additives on growth performance, livability, gut integrity, immunity, caecal microflora and footpad health in broilers challenged with subclinical necrotic enteritis (NE). Additives were: A) synergistic blend of medium chain fatty acids (MCFA), slow-release C12, target release butyrates, organic acids (OA) and a phenolic compound; B) synergistic blend of partly buffered OA with MCFA; C) synergistic blend of partly buffered OA with a high concentration of MCFA. A total of 1404 male Ross 308 chicks were assigned to 78 floor pens each stocked with 18 birds. A randomised complete block design was used with 6 treatments replicated 13 times and the treatments were: T1 - unchallenged group, without additives or in-feed antimicrobials; T2 - challenged group, without additives or in-feed antimicrobials; T3 - challenged group plus in-feed antimicrobial (Zinc bacitracin); T4 - challenged group plus additive A at 1.5, 1.5, 0.5 g/kg feed; T5 - challenged group plus additive B at 2.5, 2.0, 1.0 g/kg feed; T6 - challenged group plus additive C at 2.0, 1.5, 1.0 g/kg feed in starter, grower and finisher phases, respectively. Diets were based on wheat and soybean meal and were supplemented with xylanase and phytase. Challenged birds were given field strains of Eimeria spp. oocysts consisting of E. acervulina (5000), E. maxima (5000) and E. brunetti (2500) at d 9 and Clostridiumperfringens (Cp) at d 14 (10⁸ CFUs/mL). Mortality data were used to correct the FCR. Bird performance was measured from d 0 to 35. Serum fluorescein isothiocyanate dextran (FITC-d) was used as a leaky gut marker to measure gut integrity; immunoglobulins and caecal microflora were measured at d 16. Footpad health and litter quality (Kheravii et al., 2017) were scored at d 35.

The unchallenged group had higher feed intake (FI), body weight gain (BWG), lower FCR, and serum FITC-d concentration compared to NE challenged groups (P < 0.05). BWG and livability were not significantly different among the challenged groups. Birds supplemented with feed additives had lower FCR compared to T2 (overall, P < 0.05). On d 16, a higher concentration of serum FITC-d was observed in T2 compared to feed additives groups (P < 0.05). Birds challenged with NE had a higher level of serum IgA but no effects were observed in serum IgG and IgM levels. Birds fed additive C had lower counts of Bacteroides spp. compared to T2 (P < 0.05). Birds fed additives had lower counts of Ruminococcus spp. than T2 (P < 0.05). Cp counts were not significantly different between additives B, C, and in-feed antimicrobial groups (P > 0.05). Birds treated with feed additives had lower footpad dermatitis (FPD) and hock burn scores (HB) compared to T2 (P < 0.05). There was a tendency to improve the litter quality in the additive groups (P = 0.072). However, a strong positive correlation between litter quality and FPD (r = 0.388, P < 0.0001) and HB scores (r = 0.581, P < 0.0001) was observed. These findings suggest that additives A, B, and C were effective in alleviating the impact of NE as indicated by improved FCR, enhanced gut integrity and improved bird welfare. These results also demonstrated that the diet supplemented with additive C helped to maintain good gut health by altering the intestinal bacterial population.