Superior Growth Rates in Broilers Fed Wheat with Low In Vitro Feed-Xylanase Inhibition

Novel thermal stability enhanced xylanase improves the performance and digestibility parameters in broilers

Xylanases require thermal stability to withstand the pelleting process, pH stability to function in the gastrointestinal tract, and resistance to xylanase inhibitors in raw materials to be effective in animal feed. A GH11 family xylanase originating from an anaerobic fungus, Orpinomyces sp. strain PC-2, has high specific activity and resistance to xylanase inhibitors intrinsically. It was engineered using rational protein design methods to obtain a thermal and pH stable enzyme, OXynA-M. OXynA-M showed resistance to three types of xylanase inhibitors, Triticum aestivum xylanase inhibitors TAXI-IB and TAXI-IIA and xylanase inhibitor protein XIP and showed melting temperature of 87.2°C when measured using differential scanning calorimetry. It was stable at all pH between 2.0-10.0 incubated up to 4 h. Xylo-oligosaccharides (XOS) production profile using a wheat arabinoxylan substrate revealed the production of xylobioses up to xylohexaoses, which are known to have prebiotic functionalities. An animal trial was conducted in broiler chickens to evaluate the in vivo efficacy of the xylanase. In total, 600 1-day-old chickens were divided into six dietary treatments, including a positive control (PC) (T1) without the addition of exogenous enzyme and the rest where exogenous xylanase was added at the rates of 1200, 2400, 4800, 9600, and 240000 U/kg of feed from T2-T6. An increase in OXynA-M xylanase improved the performance parameters in the enzyme-treated groups compared with the control. The viscosity of ileal digesta decreased with increasing enzyme dosage. A significantly lower viscosity of 6.54 cP was determined for the minimum dose in T2 (1200 U/kg), and the viscosity was further reduced in T6 (240000 U/kg) (P<0.05) compared to the control treatment. The apparent ileal digestibility of crude protein, fat, and starch improved as the xylanase dosage increased. The application of OXynA-M xylanase improved the apparent ileal digestibility of crude protein when the dose was higher than that of T2 (1200 U/kg). Furthermore, the AMEn of the diets improved when xylanase was supplemented at a rate of 9600 U/kg (T5) compared with the control treatment (P<0.05).

Xylanase Inhibitors: Defense Players in Plant Immunity with Implications in Agro-Industrial Processing

Xylanase inhibitors (XIs) are plant cell wall proteins largely distributed in monocots that inhibit the hemicellulose degrading activity of microbial xylanases. XIs have been classified into three classes with different structures and inhibition specificities, namely Triticum aestivum xylanase inhibitors (TAXI), xylanase inhibitor proteins (XIP), and thaumatin-like xylanase inhibitors (TLXI). Their involvement in plant defense has been established by several reports. Additionally, these inhibitors have considerable economic relevance because they interfere with the activity of xylanases applied in several agro-industrial processes. Previous reviews highlighted the structural and biochemical properties of XIs and hypothesized their role in plant defense. Here, we aimed to update the information on the genomic organization of XI encoding genes, the inhibition properties of XIs against microbial xylanases, and the structural properties of xylanase-XI interaction. We also deepened the knowledge of XI regulation mechanisms in planta and their involvement in plant defense. Finally, we reported the recently studied strategies to reduce the negative impact of XIs in agro-industrial processes and mentioned their allergenicity potential.

Effect of age on the relationship between metabolizable energy and digestible energy for broiler chickens

A total of 960 male Ross 308 chicks (day-old) were used to investigate the effect of age on the relationship between metabolizable energy (ME) and digestible energy (DE) for broiler chickens. Bird growth variables, nitrogen retention (NR), nitrogen digestibility (ND), as well as the relative weight of liver, pancreas, and the gastrointestinal tract were determined. Practical diets that compared 2 cereals (corn and wheat) and exogenous xylanase (0 or 16,000 BXU/kg) were evaluated at 5 ages (7, 14, 21, 28, and 35 D) in a 2 × 2 × 5 factorial arrangement of treatments with 8 replicates per treatment and started with 30 birds per replicate. A randomized block ANOVA analysis of repeated measures was performed, and a 2 × 2 × 5 factorial structure was used to investigate the 2 dietary treatment factors (cereal type and the presence of xylanase) within the 5 bird ages (7, 14, 21, 28, and 35 D), and their interactions. Apparent metabolizable energy (AME) increased linearly from 7 until 28 D of age, but (P < 0.05) decreased at 35 D of age. Digestible energy was high at 7 D of age, then dropped and remained similar (P > 0.05) from 14 to 35 D of age. The AME: DE ratio was lowest (P < 0.05) at 7 D of age but there were no (P > 0.05) differences thereafter. Cereal type and xylanase supplementation did not (P > 0.05) change the ME: DE ratio. The results indicate that determining ME before 14 D of age may give absolute values that are lower than would be obtained with older birds. ME values that are determined on older broiler chickens may overestimate the energy availability of practical feeds used in broiler starter feeds.