Role of a family 11 carbohydrate-binding module in the function of a recombinant cellulase used to supplement a barley based diet for broiler chickens

Cellulases and xylanases display a modular architecture that comprises a catalytic module linked to one or more non-catalytic carbohydrate-binding modules (CBMs). CBMs have been classified into 52 different families, based on primary structure similarity. These non-catalytic modules mediate a prolonged and intimate contact of the enzyme with the target substrate eliciting efficient hydrolysis of the target polysaccharides. 2. A study was undertaken to investigate the importance of a family 11 CBM, displaying high affinities for barley -glucans, in the function of recombinant derivatives of cellulase CtLic26A-Cel5E of Clostridium thermocellum used to supplement a barley-based diet for broiler chicken. 3. The results showed that birds fed on diets containing the recombinant CtLic26A-Cel5E modular derivatives or the commercial enzyme mixture RovabioTM Excel AP displayed improved performance when compared with birds fed on diets not supplemented with exogenous enzymes. 4. It is suggested that the enzyme dosage used in this study (30 U/kg of basal diet), was probably too high for the efficacy of the family 11 CBM to be noticed. It remains to be established if the targeting effect resulting from the incorporation of CBMs in plant cell wall hydrolases may be effective at lower exogenous enzyme dosages

Crop -glucanase activity limits the effectiveness of a recombinant cellulase used to supplement a barley-based feed for free-range broilers

1. The supplementation of diets rich in soluble polysaccharides with microbial cellulases and hemicellulases decreases digesta viscosity and promotes broiler performance. 2. In contrast, recent experiments suggest that polysaccharidases are ineffective for improving the nutritive value of pasture biomass used by free-range broilers. However, the feasibility of using cellulases and hemicellulases to improve the utilisation of cereal-based feeds by pastured poultry remains to be established. 3. A study was undertaken to investigate the capacity of a recombinant cellulase from Clostridium thermocellum to improve the nutritive value of a barley-based feed for free-range pastured broilers of the RedBro Cou Nu RedBro M genotype. 4. The results show that supplementation of a barley-based diet with a recombinant -glucanase had no effect on the performance of free-range broilers, foraging in legume-based diets from d 28 to 56. In addition, the results confirm that the lack of effect of the recombinant enzyme in improving the nutritive value of the barley-based feed does not result from enzyme proteolysis or inhibition in the gastrointestinal tract. 5. Significantly, -glucanase activity was identified in the crop of non-supplemented animals. The data suggest that endogenous cellulases originated both from the barley-based feed and from the crop microflora. 6. The results presented here suggest that in older birds of slow-growing genotypes associated with free-range production systems, previously unknown sources of -glucanases, such as the feed and microbial symbiotic microflora, can affect the effectiveness of exogenous enzymes added to the feed

A family 11 carbohydrate binding module (CBM) improves the efficacy of a recombinant cellulase used to supplement barley-based diets for broilers at lower dosage rates

1. Exogenous microbial -1,3-1,4-glucanases and hemicellulases contribute to improving the nutritive value of cereals rich in soluble non-starch polysaccharides for poultry. 2. In general, plant cell wall hydrolases display a modular structure comprising a catalytic module linked to one or more non-catalytic carbohydrate-binding modules (CBMs). Based on primary structure similarity, CBMs have been classified in 50 different families. CBMs anchor cellulases and hemicellulases into their target substrates, therefore eliciting efficient hydrolysis of recalcitrant polysaccharides. 3. A study was undertaken to investigate the effects of a family 11 -glucan-binding domain in the function of recombinant derivatives of cellulase CtLic26A-Cel5E of Clostridium thermocellum that were used to supplement a barley-based diet at lower dosage rates. 4. The results showed that birds fed on diets supplemented with the recombinant CtLic26A-Cel5E modular derivative containing the family 11 CBM or the commercial enzyme mixture RovabioTM Excel AP tended to display improved performance when compared to birds fed diets not supplemented with exogenous enzymes. 5. It is suggested that at lower than previously reported enzyme dosage (10 U/kg vs 30 U/kg of basal diet), the -glucan-binding domain also elicits the function of the recombinant CtLic26A-Cel5E derivatives. 6. Finally, the data suggest that exogenous enzymes added to barley-based diets act primarily in the proximal section of the gastrointestinal tract

The effects of restricting enzyme supplementation in wheat-based diets to broilers

The performance of broilers fed on xylanase supplemented diets for part or all of the production cycle was evaluated in two experiments. In a preliminary experiment, 1-day-old chicks were fed a wheat-based diet supplemented with a commercial xylanase for the entire duration of the experiment of 28 days, or during the last 21, 14, or 7 days of the trial. In experiment 2, the growth period was extended to 36 days, and birds were fed xylanase supplemented diets for the entire duration of the experiment, or during the last 27, 18, or 9 days of the trial. In both experiments, an additional group was fed a non-supplemented control diet. Xylanase-supplemented broilers outperformed non-supplemented birds. Significant differences in body weight emerged at 21–28 days of age, suggesting that the response to xylanase supplementation occurs primarily during the latter stages of broiler growth. Broilers fed xylanase-supplemented diets for the entire experiment presented similar growth performance, intestinal viscosity, gastrointestinal enzyme activity and organ sizes when compared with birds supplemented with the exogenous xylanase for the last 14 (experiment 1) or the last 18 days (experiment 2) of the trials. Birds exposed to exogenous xylanase for the entire duration of the experiment showed, however, a non-significant trend (P<0.1) towards an improved final body weight and feed conversion ratio. Nevertheless, it appears that an early exposure to the exogenous xylanase is of marginal importance in obtaining a significant response to xylanase supplementation by broilers fed wheat-based diet

The effects of restricting enzyme supplementation in rye-based diets for broilers

The purpose of the current study was to restrict enzyme addition in order to evaluate if supplementation throughout the broiler production cycle is required. Here we analyze the possibility of circumscribing xylanase supplementation in rye-based diets to the earliest periods of the life of the broiler. In the current experiment, 1-day-old chicks were divided into 5 treatments and fed a rye-based diet supplemented with a commercial enzyme mixture containing a microbial xylanase. The five treatments consisted of birds fed a nonsupplemented diet and birds fed diets supplemented with the exogenous enzyme for the entire period of the experiment (28 days), the first 21 days, the first 14 days or the first 7 days of the trial. The data revealed that broilers fed diets supplemented with enzymes during 28 days had similar (P>0.05) growth performance, gastrointestinal enzyme activity and relative organ sizes to broilers fed supplemented diets only in the first 21 days of the experimental period. These results suggest that the action of exogenous enzymes, when used to supplement rye-based diets for broilers, may be restricted to the first 21 days of the broiler’s production cycle without compromising animal performanc