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Effects of chitosan oligosaccharides on broilers challenged with a natural subclinical necrotic enteritis model

2022 CPRF,Broilers
The removal of dietary antibiotic growth promoters (AGP) increases the risk of necrotic enteritis (NE) in broilers, and effective replacements must be found. Dietary chitosan oligosaccharides (COS) of varying molecular weights (Mw) have been tested as potential AGP replacements in broilers. Previously we reported that medium Mw COS (95 KDa) increased broiler BW after an NE challenge and tended to increase BW during the entire cycle compared to birds fed a diet without AGP, although gross intestinal NE lesion scores were not affected. From that study, samples obtained from the most promising treatments were further evaluated to determine the COS effects on cecal microbial composition and short-chain fatty acids (SCFA), mortality and footpad dermatitis (FPD). Treatments were: COS 95 KDa included at 0.2 or 5 g/kg of the diet, a positive control (PC; with antibiotic and coccidiostat) and a negative control diet (NC; without medications). Each treatment was fed to 8 replicate pens of 18 birds each. A natural sub-clinical NE challenge model (oral 15X coccidiosis vaccine dose at 12 d, and 24-hour feed removal at 18 d) was applied to all birds. Cecal contents collected at 22 d were used to determine the bacterial profile and SCFA production. Mortality was recorded daily, and FPD was measured at 38 d. The microbial profile was analyzed by Orthogonal contrasts, and the remaining data were analyzed by ANOVA with means compared by Tukey’s test at 5% probability. The mortality throughout the trial was 3.91%; 55.5% of that occurred between 18 to 24 d, similar to field cases of NE. Overall, the cecal microbial profile was not affected by treatment (by ANOVA). However, in pairwise comparisons, NC had a greater (P <0.01) abundance of Clostridium sensu stricto 1 at the genus level than the COS treatments. At the species level, COS treatments had a higher abundance of Lactobacillus oris than NC (P <0.01) and PC (P <0.01), and a higher abundance of Lactobacillus ingluviei than PC (P <0.01). PC resulted in more (4.79 μmol/ml; P= 0.03) propionate than 0.2 g/kg COS 95 KDa (2.63 μmol/ml) but was similar to 5 g/kg COS 95 KDa and NC (3.32 and 2.82 μmol/ml, respectively). Isobutyrate from the 5 g/kg COS 95 KDa group (0.58 μmol/ml; P= 0.01) was higher than in the PC (0.34 μmol/ml) and NC (0.37 μmol/ml) but was similar to the 0.2 g/kg COS 95 KDa. Dietary treatment did not affect FPD. COS 95 KDa may act as a prebiotic modulating the growth of Lactobacilli in broilers and enhance performance following an NE challenge. COS 95 KDa may be part of a strategy to replace AGP; however, further mechanistic studies are required.
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necrotic enteritis
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PhD Candidate

University of Alberta

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