Exogenous Enzymes in Poultry NutritionSupervisor: Dr. M. DaneshyarBy: M. Behroozlak

Jan. 2014

Introduction

Antibiotics have been used in poultry feed for improving growth performance, preventing some specific pathogenic microorganism and increasing some useful microorganism in intestinal microflora over the years.

However, antibiotics used as growth promoters in animal feeds have been banned recently due to potential development of antibiotic resistant human pathogenic bacteria.

Introduction

Nowadays, the possibility of using new natural alternative additives instead of antibiotics in animal diets is being researched.

PrebioticsOrganic Acids

Peptides Growth Promotores (Enzymes(

Replacements of Antibiotic Growth Promotores (AGPs(

Probiotics Phytobiotics

Exogenous Enzymes

• Traits of Exogenous Enzymes (EE(Enzymes are one of the many types of protein in biological systems. Their essential characteristic is to catalyze the rate of a reaction but is not themselves altered by it. They are involved in all anabolic and catabolic pathways of digestion and metabolism.

Enzymes are not living organisms and are not concerned about viability or cross infection. They are stable at 80-85 degree centigrade for short time.

Exogenous Enzymes

It is common practice to name enzymes by adding the suffix ase to the name of the principal substrate. For example, β-glucanase is an enzyme that splits β-glucans, and proteases break protein.

Categorize of enzymes

1. Digestive enzymes as endogenous enzymes

2. Exogenous enzymes (those administrated from

outside(

Sources of EE

Microorganisms that generally involved in production of enzymes are :

Bacteria

Fungus

Yeast

Bacillus subtilis, Bacillus lentus, Bacillus amyloliquifaciens and Bacillus stearothermophils

Triochoderma longibrachiatum, Asperigillus oryzae and Asperigillus niger

S. cerevisiae

Use of enzymes in animal feed

Consistent increase in the price of feed ingredients has been a major constraint in most of the developing countries.

As a consequence cheaper and nonnconventional feed ingredients have to be used which contain higher percentage of Non-Starch Polysaccharides (soluble and insoluble/crude fibre) along with starch.

Non Starch Polysaccharides (NSPs) are polymeric carbohydrates which differ in composition and structure from starch (Morgan et al., 1995) and possess chemical cross linking among them therefore, are not well digested by poultry.

NSPs

• A part of these NSPs is water-soluble which is notorious for forming a gel like viscous consistency in the intestinal tract (Ward, 1995) thus by reducing gut performance.

• Predominantly water soluble and viscous arabinoxylans, which belong to pentosan group, are assumed to be the factor responsible. These pentosans also greatly increase the water intake by the birds, which lead to unmanageable litter problems caused by wet and sticky droppings.

This deteriorates the hygienic conditions and carcass quality.

NSPs

On the other hand, β-glucans adversely affect all nutrients, especially protein and starch utilization and are known to give rise highly viscous conditions in the small intestine of the chicks.

Poultry do not produce enzymes for the hydrolysis of Non-Starch Polysaccharide present in the cell wall of the grains and they remain un-hydrolyzed.

The poultry industry readily accepts enzymes as a standard dietary component, especially in wheat and barley-based rations.

NSPs

Classification of NSPs

NSPs

The NSPs are the major components of the cell wall of cereals. Some of them located mainly in endosperm cell walls of cereals are soluble and others are insoluble.

NSPs

These NSPs are soluble in water producing viscous solutions (Figure 2.1). Increased viscosity of the fluid film surrounding the villi of rat jejunum gave rise to a thickening of the rate-limiting unstirred layer.

This caused accumulation of nutrients and a reduction of nutrient digestion and absorption in vitro .

Unstirred Water Layer

NSPs

NSPs not only affects the absorption of basic nutrients such as glucose, fatty acids and amino acids, but also affects the utilization of certain minerals, such as calcium, phosphorus and zinc. Studies demonstrated that the endogenous secretion of water, proteins, electrolytes and lipids can be increased markedly by adding NSPs to the diet.

Wheat

Barley

Corn

Sorghum

Defects of NSPs for poultry

NSPs Enzymes

The most important enzymes in the poultry feed industry today are β-glucanase, xylanase and phytase.

They are widely used in poultry diets containing barley, oats, rye or wheat to improve feed utilization by removal of the anti-nutritional effects of NSPs contained in these cereal raw materials.

Enzymes break down the NSPs, decreases intestinal viscosity and eventually improve the digestibility of nutrients by improving gut performance.

NSPs Enzymes improved performance

NSPs Enzymes

The Use of Enzymes in Corn-SBM Poultry Rations

The nutrients contained in corn and soybean meal are generally considered to be highly digestible. Heat treatment is commonly used to inactivate antinutritive factors (ANFs) such as protease inhibitors and lectins in soybean meal (Campbell and van der poel, 1998).

However, the energy utilization in corn and soybean meal also depends on the amount of indigestible carbohydrates present, particularly oligosaccharides.

The inclusion of high concentrations of soybean meal as the sole protein source in broiler diets can adversely affect growth performance (Irish and Balnave, 1993).

The Use of Enzymes in Corn-SBM Poultry Rations

In addition, some of ANFs in soybean, such as antigenic proteins and phytate cannot be reduced or alleviated by heat.

With the recent developments in feed enzyme technologies, many microbial enzymes such as phytase, amylase, protease and α-galactosidase, have been used into corn-soybean meal-based diet either to improve digestibility of nutrients or to reduce the ANFs.

Most of the stored phosphorus in plants is found in seeds, mainly as phytate phosphorus. In corn, 90% of the phosphorus is present as phytate, and in soybean meal 75% of the phosphorus is present as phytate

Phytate

Phytate

Phytate phosphorus is poorly available (30%) to monogastric animals, including poultry, due to the absence of adequate levels of endogenous enzyme phytase or phosphatase.

Actually, phytate is often considered toxic, or antinutritive because it is capable of binding di- and divalent cations such as Ca, Co, Cu, Fe, Mg, Mn, Ni and Zn in very stable complexes and reducing the availability of these minerals to the animal . In addition, phytate may form complexes with proteins and starches and may also reduce the availability of these nutrients from the diet .

Dietary supplementation with microbial phytase is well established as an effective and practical method of improving phytate digestibility in production animals. In poultry, microbial phytase supplementation generally results in a 20-45% improvement in phytate-P utilization.

Benefits of Enzymes

Benefits of using feed enzymes to poultry diets include :

Reduction in digesta viscosity,

Enhanced digestion and absorption of nutrients especially fat and protein,

Improved Apparent Metabolizable Energy (AME) value of the diet,

Increased feed intake, weight gain, and feed–gain ratio,

Reduced beak impaction and vent plugging,

Decreased size of gastrointestinal tract,

Altered population of microorganisms in gastrointestinal tract,

Reduced water intake, reduced water content of excreta, reduced production of ammonia from excreta, reduced output of excreta, including reduced N and P.

Effect of EE on GIT Charastristics

Effect of EE on

Digestive organ sizes

Morphometric traits of GIT

Digestive enzymes activities

Effect of EE on GIT Morphology in Wheat- SBM diet

A growth trial were conducted to investigate the effects of dietary enzyme supplementation (xylanase and β-glucanase) on, intestinal morphology, digestive organ size of broiler chickens fed wheat-based diets.

The experimental diets in both trials consisted of a wheat- soybean based control diet supplemented with 0, 200, 400, 600, 800, or 1,000 mg/kg enzyme. Diets were given to the birds from d 7 to 42 of age.

Study 1

Effect of EE on GIT Morphology

Enzyme inclusion decreased the size of the digestive organs and the gastrointestinal tract to some extent. The relative length of each intestinal segment decreased linearly (P < 0.05).

The relative weight of the anterior intestine on d 21 and ileum on d 42 also decreased linearly (P < 0.01).

On d 21 and 42, there were negative linear (P < 0.05) relationships between increasing enzyme supplementation and the relative weight of the liver and pancreas, respectively.

Effect of EE on GIT Morphology

When supplementing exogenous enzymes in the wheat control diet, a greater proportion of NSP may be hydrolyzed, which might attenuate the secretory function of the responding organs and GIT segments, and then the organ sizes may decrease.

Brenes et al. (1993) also implied that:

The reduction in relative organ weight had a direct economic benefit, as the dressing yield of broilers should increase proportionally.

Effect of EE on GIT Morphology in Corn-SBM diet

The study was conducted to compare the effects of XG (xylanase + β-Glucanase) with AG (galactosidase) and BM (β-mannanase) at different metabolizable energy diets on digestive physiology of broilers fed with corn-SBM diet.

A 2 × 4 factorial design was used with two basal diets (the positive control group, PC; negative control with ME reduction 100 kcal/kg, NC) and with or without the addition of three exogenous enzymes (No enzyme diet; 0.02% BM; 0.01% AG; 0.05% XG) respectively.

Study 2

Two diet with four enzyme levels

Effect of EE on GIT Morphology in Corn-SBM diet

For assessment of morphometric tratis:

At 21 and 42 day of age 2.0 cm-long samples from duodenum and ileum were taken to measure the villus length and crypt depth, and the villus length to crypt depth ratio (V/C) was calculated by the method of Lei (2009).

For assessment of endogenous enzymes activity :

One broiler per replicate was chosen and fed for 2 h. After 4 h feeding, the intestinal contents of the duodenum plus jejunum were collected and stored at −20°C for analysis of trypsin, chymotrypsin, lipase, and amylase activities according to the method of detection kit instructions from Nanjing Jiancheng Bioengineering Institute.

Digestive physiology:

Effect of EE on GIT Morphology in Corn-SBM diet

The crypt depth (in duodenum) was significantly decreased by the addition of enzymes (AG ) in the PC diet at 21d (P <0.05). The V/C was significantly increased by PC diet at 21 d, and the addition of AG increased V/C (P <0.05) at 21d (Table 6).

The villus length and V/C of ileum were significantly increased by the addition of BM or XG (Table 7).

XG improved the activities of trypsin, chymotrypsin and amylase, BM improved the activity of trypsin at 21d, and AG improved the activity of chymotrypsin at 21d (Table 8).

Results:

Crypt depth

Large crypt suggests a high nutrient requirement for intestinal maintenance and reduced efficiency of then bird and explain the poor growth performance. It has been reported that enzyme supplementation can lower the rate of cell proliferation in the crypt (Silva and Smithard, 2002).

The lower crypt depth as a result of enzyme addition can be considered as a beneficial way to decrease the cost of intestinal maintenance in birds.

Villi & Crypt depth

Effect of EE on GIT traits & Blood metabolites

There were four treatments: the control diet and the other three enzyme complex supplemented diets which were 180 mg/kg, 360 mg/kg and 720 mg/kg enzyme complex supplemented to the control diet, respectively.

Enzyme complex :The enzyme complex contained mainly neutral protease (3,000 U/g), acid protease (3,000 U/g), endoamylase (500,000 U/g) and xylanase (65,000 U/g). It also contained lower amounts of exoamylase, β-glucanase, pectinase, cellulase and cellobiase.

Study 3

Effect of EE on GIT traits & Blood metabolites

The birds fed the diets supplemented with 180 mg/kg and 360 mg/kg enzyme complex had better performance and nutrient availability, the activities of amylase and trypsin in the digestive tract in the two treatments were improved, the villus height and surface area of villus in the small intestine increased and the crypt depth and epithelial thickness of small intestine decreased.

Relative weights of pancreas and relative weights and lengths of small intestine decreased.

Results:

Surface are of villus: VW/2×VL×2π

Blood Metabolites

Friesen et al. (1992) found that enzyme complex increased the digestion rate of starch, while the product of starch digestion was absorbed into blood in the form of glucose and so increased blood sugar content.

Borg et al. (1987) reported that blood urea nitrogen could accurately reflect the state of protein metabolism and balance of amino acids, and urea nitrogen was low when the balance of amino acids was good.

About Blood sugar & Blood Urea nitrogen

Conclusion

The biggest single expense in any system of poultry production is feed accounting for up to 70% of total production cost per bird. Poultry naturally produces enzymes to aid the digestion of feed nutrients. However, they do not have enzyme to break down fibre completely and need exogenous enzymes in feed to aid digestion.

Consequently exogenous enzymes are a very useful tool in the improving of physiological and metabolic mechanisms in GIT espacially in NSP-based diets.