A simple model for predicting the response of chicks to dietary enzyme supplementation

The evolution and application of enzymes in the animal feed industry: the role of data interpretation

1. Enzymes have been used commercially for nearly 40 years and save significant costs through sparing of expensive nutrients but the mechanism by which this is achieved is still debated. 2. The research focused on non-starch polysaccharidase (NSPase) enzymes is used as an example of where greater progress could have been made if the details of the work had been described more fully and the analysis of the data generated had been broader in scope and more critical. 3. Lack of standardisation of the details presented in the materials and methods has been identified as a significant barrier to meaningful retrospective analysis and thus limits advances in the understanding of the mode of action of these enzymes. 4. The identity of the enzyme employed and its activity is often lacking, and more importantly the purity is rarely disclosed. Contaminant activities which are neither listed nor assayed could play a significant role in the responses observed. 5. The dose optimum of most enzymes is often considerably higher than that employed in most studies. Thus studies claiming synergy between two 'activities' should ensure that the response is not related to each enzyme simply augmenting the dose of just one activity in the finished feed. This is a common problem, and coupled with the lack of factorial experiments to justify the presence of each enzyme in a multi-enzyme product, it is not surprising that there is still debate as to whether single or multi-enzymes are best suited poultry rations. 6. The three proposed mechanisms for NSPases (viscosity, cell wall and prebiotic) are discussed, and along with their strengths and weaknesses it is suggested that a re-evaluation of each is needed. Viscosity may have to be re-evaluated as being a function not only of the cereal being fed, but of the age of the animal as well. The cell wall theory as described is poorly modelled in vitro and hence the validity of these data is questioned. The prebiotic theory may need significant modification as it appears that the quantities of oligomers produced are insufficient to generate the additional volatile fatty acids (VFA)'s reported. It is likely that all three mechanisms play a role in the responses observed, but the prebiotic mechanism probably plays by far the most important part in low viscosity diets. 7. Future research would be improved if it considered all potential mechanisms when designing a trial. Significant failings are apparent as a result of adherence to tenets in explanation of the results. Most importantly, it should be emphasised that a hypothesis is there to be tested, not defended.

Catalytic properties, functional attributes and industrial applications of β-glucosidases

β-Glucosidases are diverse group of enzymes with great functional importance to biological systems. These are grouped in multiple glycoside hydrolase families based on their catalytic and sequence characteristics. Most studies carried out on β-glucosidases are focused on their industrial applications rather than their endogenous function in the target organisms. β-Glucosidases performed many functions in bacteria as they are components of large complexes called cellulosomes and are responsible for the hydrolysis of short chain oligosaccharides and cellobiose. In plants, β-glucosidases are involved in processes like formation of required intermediates for cell wall lignification, degradation of endosperm’s cell wall during germination and in plant defense against biotic stresses. Mammalian β-glucosidases are thought to play roles in metabolism of glycolipids and dietary glucosides, and signaling functions. These enzymes have diverse biotechnological applications in food, surfactant, biofuel, and agricultural industries. The search for novel and improved β-glucosidase is still continued to fulfills demand of an industrially suitable enzyme. In this review, a comprehensive overview on detailed functional roles of β-glucosidases in different organisms, their industrial applications, and recent cloning and expression studies with biochemical characterization of such enzymes is presented for the better understanding and efficient use of diverse β-glucosidases.

Multicarbohydrase Enzymes for Non-ruminants

The first purpose of this review is to outline some of the background information necessary to understand the mechanisms of action of fibre-degrading enzymes in non-ruminants. Secondly, the well-known and understood mechanisms are described, i) eliminating the nutrient encapsulating effect of the cell wall and ii) ameliorating viscosity problems associated with certain Non Starch Polysaccharides, particularly arabinoxylans and β-glucans. A third, indirect mechanism is then discussed: the activity of such enzymes in producing prebiotic oligosaccharides and promoting beneficial cecal fermentation. The literature contains a wealth of information on various non starch polysaccharide degrading enzyme (NSPase) preparations and this review aims to conclude by discussing this body of work, with reference to the above mechanisms. It is suggested that the way in which multi- versus single-component products are compared is often flawed and that some continuity should be employed in methods and terminology.

Effects of a mono-component endo-xylanase supplementation on the nutritive value of wheat-based broiler diets

1. Two trials were conducted to evaluate the effects of a mono-component thermostable endo-1,4-β-xylanase derived from Thermomyces lanuginosus on the nutritive value of wheat-based broiler diets. In a 5-week growth trial, the efficacy of xylanase supplementation at 0, 100, 150, 200, 400 and 4000 FXU/kg diet was evaluated. A short-term balance trial was carried out according to a 4 × 2 factorial arrangement of treatments, involving 4 wheat cultivars and endo-xylanase at 0 or 200 FXU/kg. 2. In the growth trial, enzyme supplementation from 0 to 400 FXU/kg reduced feed intake and improved feed conversion linearly. Digesta viscosity was significantly reduced by all enzyme inclusion levels by 49·6-56·9%, in a quadratic manner. 3. In the balance trial, xylanase supplementation resulted in a significant improvement of protein, lipid and dry matter apparent digestibility coefficients of diets, accompanied by improved dietary AME(N) values. There was a significant wheat × enzyme interaction on AME(N) and lipid digestibility. There was a significant effect of wheat cultivar on dry matter digestibility.

Microbial beta-glucosidases: cloning, properties, and applications

Beta-glucosidases constitute a major group among glycosylhydrolase enzymes. Out of the 82 families classified under glycosylhydrolase category, these belong to family 1 and family 3 and catalyze the selective cleavage of glucosidic bonds. This function is pivotal in many crucial biological pathways, such as degradation of structural and storage polysaccharides, cellular signaling, oncogenesis, host-pathogen interactions, as well as in a number of biotechnological applications. In recent years, interest in these enzymes has gained momentum owing to their biosynthetic abilities. The enzymes exhibit utility in syntheses of diverse oligosaccharides, glycoconjugates, alkyl- and aminoglucosides. Attempts are being made to understand the structure-function relationship of these versatile biocatalysts. Earlier reviews described the sources and properties of microbial beta-glucosidases, yeast beta-glucosidases, thermostable fungal beta-glucosidase, and the physiological functions, characteristics, and catalytic action of native beta-glucosidases from various plant, animal, and microbial sources. Recent efforts have been directed towards molecular cloning, sequencing, mutagenesis, and crystallography of the enzymes. The aim of the present article is to describe the sources and properties of recombinant beta-glucosidases, their classification schemes based on similarity at the structural and molecular levels, elucidation of structure-function relationships, directed evolution of existing enzymes toward enhanced thermostability, substrate range, biosynthetic properties, and applications.

Development of a multipurpose feed enzyme analyzer to estimate and evaluate the profitability of using feed enzyme preparations for poultry

Previous studies have demonstrated that a log-linear equation could accurately predict chick performance when a feed enzyme was added to a diet and that the slope of the equation provided a measure of the efficacy of different enzymes. The objective of the study was to develop a software package, a Multipurpose Feed Enzyme Analyzer (MPFEA), based on an equation designed to evaluate the profitability of using feed enzymes. A high correlation between the efficacy of different feed enzymes (B values, the slopes of the equations) and the maximal profits was obtained when feed enzymes were added to a barley-based diet (r2 = 0.99, P < 0.0005). In contrast, there was a low correlation between the B values and the maximal profits when a feed enzyme was added to different cereal-based diets (r2 = 0.61, P = 0.2171). It appeared that there is not always a close association between efficacy of an enzyme when added to different cereal-based diets and the corresponding profitability. The MPFEA was highly versatile, as any combination of inputs such as the amounts of a feed enzyme and a substituted cereal required to yield a profit level could be determined. In conclusion, the MPFEA can accurately evaluate profitability of using different feed enzymes; select the most profitable cereal for a given feed enzyme; determine the optimal amounts of a feed enzyme, a cereal, or both; and even estimate the alternate price for a feed enzyme and a cereal. It should provide a useful tool for nutritionists.

Prediction of the effect of enzymes on chick performance when added to cereal-based diets: use of a modified log-linear model

A previous study demonstrated that a log equation could be used to predict the relationship between the amount of a crude enzyme added to a diet and chick performance. The objective of the current study was to determine if a modification of the original equation, in conjunction with a computer program, would overcome some of its limitations. The modified equation was Y = A + B log (CX + 1), where Y is the estimated performance value; A is the intercept that represents the performance without enzyme supplementation; B, the slope of the equation (performance change per log unit of an enzyme in the diet), is a measure of an enzyme efficacy; C is an amplified factor; and X is the amount of enzyme in the diet. The results demonstrated that the new model more accurately predicted chick performance than that of the original equation with correlations (r) between chick performance and amount of different enzymes added to the diet ranging from r = 0.80 to 0.99 (P < 0.05). In addition, the same trends were found when the model was used to assess the efficacy of a given enzyme added to corn-, wheat-, barley-, and rye-based diets or for combinations of two dietary components (rye and wheat). The model proposed in this study provides a new means of assessing the overall efficacy of an enzyme preparation. This model could be routinely used by enzyme and livestock producers to establish the best combination of different cereals and enzymes so as to maximize net returns.

Evaluating the efficacy of enzyme preparations and predicting the performance of leghorn chicks fed rye-based diets with a dietary viscosity assay

We studied whether a single-step dietary viscosity assay could be used to evaluate the efficacy of an enzyme when added to a poultry diet. The results demonstrated a linear relationship between the log of the dietary viscosity change in vitro, as determined with the new assay and the log of the enzyme activity (xylanase) added to a rye-based diet. The sensitivity of the dietary viscosity assay was high, as little as 0.19 U of xylanase per gram of diet could be detected. In addition, there was a high correlation (r > or = 0.97; P < 0.005) between chick performance and the log of the amount of enzyme added to the diet or the log of its viscosity change in rye-based diets that contained different amounts of xylanase, as determined by the in vitro dietary viscosity assay. Further, the dose response data from the dietary viscosity assay, when incorporated into a log-linear model that we developed, was able to distinguish between the efficacy of two enzymes with regards to their ability to hydrolyze the viscosity factor in rye grain. Therefore, it was possible to accurately evaluate the efficacy of enzyme preparations in a rye diet and to predict chick performance using the new assay in conjunction with a model equation.