Supplementation of Fibre-Degrading Enzymes to Wheat- or Maize-based Diets Offered to Broiler Chickens under Necrotic Enteritis

A study was conducted to investigate whether the functional oligosaccharides released in situ as a consequence of fibre-degrading enzyme application ameliorate the severity of necrotic enteritis (NE) in broilers offered wheat- or maize-based diets. Day-old Cobb 500 mixed-sex broilers (n = 1536) were assigned to a 2 × 2 × 4 factorial arrangement of treatments, with six replicates per treatment, for 21 days. Factors were cereal type (wheat or maize), NE challenge (without or with), and four fibre-degrading enzyme treatments (no enzymes, family 10 xylanase, family 11 xylanase or mannanase). The NE challenge was induced by orally inoculating birds with 1 mL of Eimeria spp. on d 9, followed by oral inoculation of 1 mL C. perfringens on d 14 and 15. Body weight and feed intake were measured on d 0 and 21, and feed conversion ratio (FCR; corrected for mortality) was calculated. Normal distribution of the data was confirmed and a generalised mixed model used to test main effects, 2- and 3-way interactions at P< 0.05, using IBM SPSS Statistics 25. Tukey’s HSD test was used to separate means. Percentage of male birds in each pen was used as a covariate.

A three-way interaction was observed for d 0-21 weight gain (P=0.026) and FCR (P=0.001). Enzyme supplementation improved weight gain and FCR in birds fed the wheatbased diet, regardless of NE challenge. Unchallenged birds offered the maize-based diet with supplemental enzymes presented improved weight gain and FCR compared to those offered the maize-based diet without enzymes. However, NE challenged birds offered the maize-based diet supplemented with either family 10 or 11 xylanases presented poorer FCR compared to those offered the maize-based diet without enzymes.

This study presented evidence that, in the absence of NE challenge, xylanase and mannanase induced positive effects on bird performance, regardless of diet type. However, in the presence of NE challenge, xylanase exacerbated the negative impact of NE on weight gain and feed efficiency, but only in birds fed maize-based diets. A possible explanation is that the xylanase solubilised the insoluble NSP in maize at the beginning of the gastrointestinal tract, providing fuel for the pathogenic bacteria. This effect was not observed with wheat, possibly due to its higher soluble NSP composition, and therefore greater oligomer production in the presence of xylanase. Further research is warranted to examine this theory and assess oligosaccharide production in different dietary combinations and environments.

Figure 1 – Necrotic enteritis challenge × grain type × enzyme three-way interactions for overall (d 0 – 21) weight gain (P=0.026) and feed conversion ratio (p=0.001).