The exogenous enzymes are used in feed to reducing the antinutritional effects of dietary fiber in poultry feed. The enzymes can also be beneficial as growth promoters instead of antibiotics. Enzymes have been tried alone and in combinations with other additives such as organic acids to maintain health and production of broilers. Although the role of enzymes in improving feed utilization, growth, meat quality and economics has been well reported, their quality, consistency and reproducibility have been questioned by many researchers. This review include the enzymes information and uses in the poultry nutrition. Enzymes are biological catalyst which composed of minerals, Amino acids and vitamins.
(Key words: poultry, enzyme, growth promoter)
Introduction:
Enzymes are biological catalysts that perform some essential functions in living organisms. These enzymes are naturally in living organisms and they can produced by aerobic or anaerobic cultures of media. The primary reason of phytase enzymes using in poultry/animal feed has been free from phosphorus from phytic acid in the plant-derived sources (Ravindran et al., 1995; Bedford and Schultz, 1998). Phytase can be derived from many other sources (Liu et al., 1998), and in lasts years phytase have been commercialized
The enzymes have been used for the last 50 years but their use in animal feeds has received more attention in the last 20 year,s (Partridge and Wyatt,1955) Enzymes, even in small quantities, can initiate or accelerate the rate of chemical reactions that transform dietary substrates into products of biological significance for broiler growth and production (Taylor-Pickard,2008).The pelleting process has effects on the nutritional and handling characteristics of the feed, but the high temperatures that result (from 65 to 95°C) can inactivate heat-sensitive nutrients/ enzymes (Pickford, 1992). Phytase can decompose phytate in the feedstuffs and release phytate phosphorus, efficiently increasing the utilization of phytate phosphorus and reducing the phytic acid' santinutritional ability in the feed. The reason for using phytase enzymes in feed has been to separate the phosphorus from phytic acid in plant-derived ingredients (Ravindran et al., 1995; Bedford and Schultz, 1998). Phytase enzymes can be derived from many different sources (Liu et al., 1998).Soya bean meal produced by extraction with ethanol,rather then hexane,has these NSP's removed.Enzymes designed to improved carbohydrate digestibility of soyabean meal there fore have great potential in poultry nutrition.(Raney etal., 2009)
Cellulose is hydrolyzed through a difficult process involving cellulases, and specific enzymes include to cellulase activity. The major enzymes included in hydrolysis of cellulose is cellulase.Xylanase is a class of enzymes produced by microorganisms to break down the component of plant cell walls called as hemicellulose. Enzymes, even in small quantities, can initiate or accelerate the rate ofchemical reactions that transform dietary substrates intoproducts of biological significance for broiler growth andproduction (Taylor-Pickard, 2008). It is essential to find enzymes which are consistently e ective in enhancing the utilisation ofcereal grains in poultry diets (Scott et al.,1998). High inclusion of cereal grains may cause poor growth, less effecient digestive system, increased activity of harmful gut becteria, sticky droppings, poor feed conversion ratio and carcass quality low in broiler birds.Enzymes can overcome these problems by increasing the digestibility and reducing the amount of excreta in broilers. Thus, enzymes not only enhance the performance of birds but also help in reducing the en vironmental pollution by decreasing the excreta and moisture contents (Choct,2006 ). The benefits depends upon the nature of dietary components, processing, particle size and the compatibility of different enzymes with the dietary substrates (Acamovic,2001)
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Enzymes:
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 metabolic pathways of the digestion and metabolism. Enzymes tend to be very specific catalysts that act on one or, at most, a limited group of compounds known as substrates. Enzymes are not living organisms and are not concerned about viability or cross infection.
Enzymes Used in Poultry Feeds
Enzymes
Substrate
ß-glucanases
Barley Oats
Xylanases
Wheat, Rice bran
ß-galactosidases
Grains
Phytases
Plant feed couces
Proteases
Proteins
Lipases
Lipids
Amylases
Starch
(Adapted from: J. Anim. Pl. Sci. 16(1-2): 2006)
. Therefore, we need to match the amount of enzyme with the quantity of substrate (Acamovic and McCleary, 1996). For example, pancreatic lipase, which splits fat or lipid into glycerol and fatty acids, is an endogenous enzyme. Those enzymes added to feed as a supplement are exogenous (Classen, 1996; Classen and Bedford, 1991). Enzymes have been approved for the use in poultry feed because they are natural products of the fermentation and therefore pose no threat to the animal or the bird. Their use in the poultry feeds has predominantly related to the break down of fibre or nonstarch polysaccharide fractions in cereal . These NSPs cannot be digested by using enzymes of poultry feed and have antinutritive effects. These NSPs can bind a lot of water, and as the result, of the viscosity of the fluids in the GIT is increased. The increased viscosity causing problems in small intestine because it decreases the substrate-enzyme interaction, which decreases nutrient availability (Friesen et al. 1992) and results in the increased amounts of sticky droppings (Boros et al. 1995)
Function of Enzymes
Enzyme
Function
Phytase
Release phosphorus in phtate.
Protease
Improve protein digestibility
Pectinase
Reduce digestive viscosity
Xylanase
Break down fiber
cellulase
Break down fiber
Beta Glucanase
Break down fiber
Alpha-amylase
Improve starch digestibility
Lipase
Improve fat obsorption
(Adapted from http://www.bioproton.com.au/site/index.cfm?display=279112)
Benefits of Enzymes:
Benefits of using feed enzymes to poultry diets include; reduction in digesta viscosity, enhanced digestion and absorption of nutrients which improved Metabolizable Energy (ME) value of the diet, feed intake increases, and feed-gain ratio, weight gain, reduced beak impaction and vent picking, decreased size of GIT tract, altered population of microorganisms in GIT tract, water intake less, reduced water in excreta, ammonia production reduced from excreta, including reduced N and P (Campbell et al. 1989; Jansson et al. 1990). The main goals of enzyme supplementation in poultry diets are remove or destroy the antinutritive factors of cereals; to enhance the overall digestibility of feed; to render certain nutrients biologically more available; and to reduce pollution from animal excreta by reducing dry-matter excretion. To achieve these goals, enzymes must be able to survive the processing feeds and resist the acidic conditions and proteolytic enzymes in proventriculus and gizzard. Under practical feed mill conditions, the steam used during pelleting is responsible for lost enzyme activities. Enzymes can be quite stable under the dry heat of 90 °C for 30 min if moisture is added in the form of steam at 95 °C for 15 min, but almost 80% of activity is lost (Inborr and Bedford 1994). However, bird performance may be unaffected if feeds are conditioned before pelleting at temperatures below 85 °C.
Benefits of Enzymes
Enzyme
Benifits
Phytase
Improve feed conversion ratio
Protease
Improve litter(less wet dropings and odour)
Pectinase
Great uniformity
Xylanase
Reduce feed cost
cellulase
Use cheaper feed
Beta Glucanase
Reduce DCP used and cost
Alpha-amylase
Reduce phosphorus and Nitrogen excreation
Lipase
Improve animal wellbeing(reduce mortality and antibiotic use)
(Adapted from http://www.bioproton.com.au/site/index.cfm?display=279112)
Effects of phytase on broilers:
Phytase supplementation increased the availability of phosphorus and Ca (Rezaei, et al., 2007; Schooner, et al.,1991; Broze, et al., 1994; Kornegay, et al) Similarly, phytase increased the availability of nutrient, when was included at rate of 500 PU /Kg phytase. Toe ash , and toe ash Ca and P percentages were increased with the addition of phytase in both sexes but without significant effect on blood phosphorus concentration (Rezaei, et al., 2007). In another study when phytase was added at the level of 250PU/Kg to a low P broiler diets it increased body weight gain and feed conversion efficiency, more Ca and P in tibia ash and Ca and phosphorus retention was significantly increased (Mondal, et al.,2007). However, inclusion of phytase had no effects broilers growth performance and body levels of Ca and P (Akyurek, et al., 2005). When phytase was added to a corn based diet had a significant increase in body weight in the broiler fed for 49 days (Huff, et al.,1998).Serum activity of alkaline phosphates was significantly decreased in the diet supplemented with phytase, while serum cholesterol was significantly decreased (Huff, et al., 1998). When phytase was added to broiler diets at level of 600 ppm had no effects on broilers growth (Hussein, 2005).
It has been reported that phytase supplementation improved N retention in broiler chickens (Farrell, et al., 1993). Shirley, et al., (2003) indicated that broilers consuming a total P-deficient corn soybean meal diet can achive maximum performance when phytase is supplemented at 12000 PU\Kg diet and that current phytase supplementation levels within the poultry industry may need to be reevaluated.
Effects of phytase on layer hen feed:
This effect was investigated by several researchers. Ciftci, et al., (2005), Musapuer, et al., (2005) reported that phytase supplementation had a positive impact on hen's general performance and egg production. It was concluded that phytase supplementation to hens with P deficient diets improved P and Ca retention.. Both egg production and egg average weight were improved by addition of phytase to low P diets (Scott, et al., 1999). However, Peter, (1992) reported that feeding laying hens a low nonphytate phosphorous (NPP) diet supplemented with phytase significantly high egg production, egg weights and consumption of feed compared to hens that consumed the low nonphytate phosphorous diet free of phytase. Similarly, supplementation of phytase in diet caused an increase in egg production and a significant decline in number of broken eggs and premature egg production rates (Lim et al., 2003).It has been also reported that phytase supplementation improved N retention in laying hens (Vander Klis and Verteegh, 1991).
There are two good reasons for supplementing poultry feeds with phytase. The first reason is to decrease the harmful environmental effect of phosphorus from manure in areas with intensive production. Several studies show that optimizing phosphorus inclusion and digestion with phytase decrease the phosphorus to release in the manure to around 30%.The second reason is based that phytate is the capable of making complexes with the proteins and inorganic cations such as Ca, magnesium, iron and zinc. Using the phytase not only releases the bound phosphorus but also the other nutrients which leeds to higher nutritional value of the feed (Boling et al.,2000a ; Keshavarz, 2003; Ceylan et al., 2003; and Panda et al. , 2005). Plumstead (2007) illustrated that adding phytase to low non-phytate phosphorus increased eggs hen housed , hen day egg production (%) , fertility (%) and feed per dozen eggs of breeders.Wet litter is due to the use of newly harvested wheat and barley which can result in the increased chances of dirty egg shells and producing ammonia in farm. Enzymes are added in both barley-based diets and wheat has been shown to reduce the moisture in the fecal matter in layers (Marquardt et al. 1994).
Impact on Environment:
Enzymes have been approved for the use in poultry feed because they are natural products of fermentation and therefore pose no threat to the animal or the consumer. Enzymes will not only enable poultry producers to economically use new feedstuffs, , as they reduce pollution among with animal/poultry production.
As well as contributing to improved poultry production, feed enzymes can have a positive impact on the environment. In areas with the intensive poultry production, the phosphorus output often high, resulting in environmental problems such as eutrophication. This happens because most of the phosphorus contained in typical feedstuffs exists as the plant storage form phytate, which is indigestible for poultry. The phytase enzyme frees the phosphorus in feedstuffs and also achieves the release of other minerals (e.g. Ca, Mg), as well as proteins and amino acids bound to phytate. Thus, releasing the bound phosphorus in feed component, phytase reduces the quantity of inorganic phosphorus needed in diets, makes more phosphorus available for the bird, and decreases the amount excreted into the environment.
Use of Protease in feed:
Protease is a enzyme which digest the protein that breaks the storage of proteins binding starch in different feed ingredients. This provides the energy from break down of bound protein starch available to bird to be used for the purpose of production. Proteases is also effective in releasing protein found in ingredients like soybean meal. function of the proteases provision of the more proteins easily available.
The gathering of protease, phtase xylanase, and enzymes together working for different bad digestible nutrient of feed ingredients higher energy available for egg production and growth. Inclusion of these enzymes of the diet in gathering the typically increases available of energy to birds 3-5%.Energy is the most expensive diet nutrient , amylase addition, xylanase addition, and protease enzymes in poultry feeds provides the opportunity to decrease feed costs. Typically, reduce costs feed of enzyme supplementation
Use of Xylanases in feed:
xylanases are currently added to commercial wheat-based compound feed for broilers in order to improve growth and feed conversion ratio. The major nonstarch polysaccharide (NSP) fraction in wheat, results in a reduction of intestinal viscosity.Enzymes are hypothesized to work in 2 steps, described as an ileal phase and a cecal phase (Bedford, 2000). During the ileal phase, enzymes remove fermentable substrates. During the cecal phase, degradation products of sugars, such as xylose and xylo-oligomers, are fermented by cecal bacteria, thus stimulating the production of VFA and the growth of specific beneficial bacteria (Bedford, 2000). The presence of viscous polysaccharides increases the microbial activity in the small intestine associated with poor broiler growth performance (Wagner and Thomas, 1978; Choct et al., 1996; Langhout et al., 1999).
Microbial bile acid deconjugation, leading to an impaired lipid digestion, has been suggested to be partly responsible for poor broiler performance. Many indigenous bacteria, including lactobacilli, enterococci, clostridia, and bacteroides, are able to catalyze bile acid deconjugation (Masuda, 1981; Klaver and van der Meer, 1993; Smits etal., 1998). Among these bacteria, Streptococcus faecium and Clostridium perfringens have been shown to be very active regarding bile acid deconjugation and have been suspected to be primarily responsible for depression of chicken growth (Stutz and Lawton, 1984; Knarreborg etal., 2002). Until now, no information has been available as to whether and in which way the feeding of whole wheat and the dietary addition of xylanase influence the composition and activity of the broiler gastrointestinal microflora.
Using Enzymes to Improve Meat Quality:
Many researches (Bedford 2000; Ponte et al.,2004 ; Buchanan et al.,2007 ;Gruzuauskas et al.,2007) ) have shown that enzymes used in broiler diets can increase production. However, the information on the meat quality of birds consuming enzyme based diets is not necessary. Therefore, a more coordinated approach to study the impact of enzymes on broiler meat quality is required.The use of alfalfa in feed for monogastric is limited by the fiber content high. it is well known that alfalfa is a natural source of xanthophyll which could increase a desirable orange-yellow colour to broiler meat.
Ponteet al ( 2004) reported that the addition of cellulase and xylanase not only improved the nutritive value of alfalfa based feed but also the skin pigment broiler consuming these feed. This aspect of meat colour could be of interest to people who prefer organic chickens with a more desirable skin colour by using natural rather than the synthetic products. Some sensory tests to compare the use of synthetic versus natural colours by using enzymes on broiler meat may be helpful in the future.
Conclusion:
Enzyme supplementation has been shown to improve the productive value of feeds and to allow the use of more novel feedstuffs without loss of performance.When enzymes are used with wheat- and barley-based diets, the enzymes can, on average, improve the nutrient availability by 5 and 10%, respectively.Using exogenous enzymes in diets can also improve the growth performance and meat quality of chickens.The provision of phytase, xylanase andprotease was the efficient to increase metabolizable energy. This permits the better formulation of the rations using a wider range of ingredients.The advancement in this field must be improve for poultry and reduce the conserve resources and production of wastes.
