FEED ADDITIVES IN POULTRY

REVIEW                                                                                 Assiut University web-site: www.aun.edu.eg

FEED ADDITIVES IN POULTRY

HADEEL M. HAMEED

Department of Physiology, Biochemistry and Pharmacology, College of Veterinary Medicine, University of Mosul, Iraq.

Received: 29 December 2020;     Accepted: 28 February 2021

INTRODUCTION

The rapid development in the poultry industry and the improvement of the production efficiency have led to an increase in the use of feed supplements, which have become widely available in poultry diets for many years. The poultry industry tends to elevate  the  output  of  eggs  and  meat,  but

Corresponding author: Hadeel M. Hameed

E-mail address:  dochadeel1979@gmail.com 

Present address: Department of Physiology, Biochemistry and Pharmacology, College of Veterinary Medicine, University of Mosul, Iraq.

while preserving the health of the animal and the consumer. The use of antibiotics in avian rations for the purpose of stimulating growth is useful in improving production and preventing infections but the excessive use of these antibiotics led to raise in bacterial resistance to diseases in addition to the accumulation of remnants of these drugs in animal products and therefore they were dispensed (Nisha, 2008). The elimination of antibiotics utilize as evolution stimuli in poultry ration led to the emergence of pathogens with economic losses in poultry farms. Therefore, the search for plant extracts with medicinal properties was directed to be included in avian diet as growth stimuli (Alloui et al., 2013). The component of the active materials in these compounds varies heavily related to the plant portion used (leaves, roots, flowers and buds), the geographical origin and the harvest season (Windisch et al., 2008). The use of supplements is subject to certain criteria, as these additives are applied in healthy animal farms for the purposes of feeding and improving production, unlike veterinary drugs that are used in the pathological case under veterinary surveillance for a restricted period and followed by a limited expectation time (EFSA., 2006). The nutritional benefit of the raw substance available to feed poultry flocks is restrict related to the size and quality of the microflora of the gut of the host bird and its ambience, avian do not possess microbiota able of destroying all nutrients, as these birds are distinguishes by limited immunity to resist infectious diseases due to the concentration of pathogenic microorganisms (Yegani and Korver., 2013). Studies have showed that, antibiotic alternatives (prebiotics, probiotics, enzymes, organic acids, external emulsifiers) have some positive regulatory and antioxidant effects of intestinal flora in poultry production, and these compounds can be considered as growth stimuli if their therapeutic and toxic effects are evaluated in addition to its interaction with drugs (Jatinder et al., 2020).

Preserving the health of the animal and the consumer. The use of antibiotics in avian rations for the purpose of stimulating growth is useful in improving production and preventing infections but the excessive use of these antibiotics led to raise in bacterial resistance to diseases in addition to the accumulation of remnants of these drugs in animal products and therefore they were dispensed (Nisha., 2008). The elimination of antibiotics utilize as evolution stimuli in poultry ration led to the emergence of pathogens with economic losses in poultry farms. Therefore, the search for plant extracts with medicinal properties was directed to be included in avian diet as growth stimuli (Alloui et al., 2013). The component of the active materials in these compounds varies heavily related to the plant portion used (leaves, roots, flowers and buds), the geographical origin and the harvest season (Windisch et al., 2008). The use of supplements is subject to certain criteria, as these additives are applied in healthy animal farms for the purposes of feeding and improving production, unlike veterinary drugs that are used in the pathological case under veterinary surveillance for a restricted period and followed by a limited expectation time (EFSA., 2006). The nutritional benefit of the raw substance available to feed poultry flocks is restrict related to the size and quality of the microflora of the gut of the host bird and its ambience, avian do not possess microbiota able of destroying all nutrients, as these birds are distinguishes by limited immunity to resist infectious diseases due to the concentration of pathogenic microorganisms (Yegani and Korver., 2013). Studies have showed that, antibiotic alternatives (prebiotics, probiotics, enzymes, organic acids, external emulsifiers) have some positive regulatory and antioxidant effects of intestinal flora in poultry production, and these compounds can be considered as growth stimuli if their therapeutic and toxic effects are evaluated in addition to its interaction with drugs (Jatinder et al., 2020).

Phytogenic compounds

Phytogenic compounds are natural compounds with biological properties derived from plants that have favorable influence on the health and growth of avians (Windisch et al., 2008), and are considered a modern class of feed additives that have received widespread interest in the chickens industry (Abd El – Hack et al., 2016). Plants and herbal extracts contain many bioactive substance like alkaloids, flavonoids, soaps, phenolic substances and polypeptides (Al-Yasiry and Kiczorowska, 2016). The mechanism of action of these compounds was different due to the multiplicity of their types as they have antibacterial effects, immune stimuli, antioxidants and growth stimuli (Abd El-Hack and Alagawany, 2015).

Antioxidant effect of phytogenic compounds

The antioxidant effect of phytogenic compounds was closely related to the essential oils present in these compounds (Alagawany et al., 2016), which leads to an improvement in the physiological performance of birds, food conversion ratio, safety and quality of meat (Dhama et al., 2015). It was also noted that, the addition of essential oils to avian ration led to an elevated in production of egg with improvement in physiological performance (Bozkurt et al., 2009). The need to use natural antioxidants has become necessary due to their importance in reducing oxidative stress and many diseases (Kim et al., 2015). The antioxidant effect of these materials was due to their free radical scavenging role in the addition to increasing the level of glutathione and catalase and reducing the level of malondialdehyde (Bharavi et al., 2010). Where Labaque et al. (2013) showed that, the administration of thyme at a dose of 80 mg / bird / day led to an improvement in the productive characteristics of the quails subjected to stress. Inaddition Safa (2014) showed that adding a blend of hot red pepper and black pepper at different concentrations to the ration of broiler increased the percentage of dressing percentage. In related study, Abdel-Wareth and Lohakare (2014) indicated that the addition of mint leaves at a concentration of 5, 10,15 and 20 g / kg feed for 12 weeks in laying hens' diets at 64 weeks of age led to raised in the production, weight and mass of eggs. Cho et al. (2014) stated that adding thyme to broiler ration at a concentration of 259 mg / kg of feed resulted in a significant decrease in the numbers of Salmonella and E. coli in the gastrointestinal tract.

Influence of phytogenic compounds on nutrient digestion and make up the digestive system

Many herbs and medicinal plants have multiple effects on the gastro-intestinal tract, including anticolic and laxative, as it was observed that preparing broiler ration with mint at a concentration of 200 mg / kg led to an increased in protein digestion (Emami et al., 2012). Several studies indicated that, thyme, cinnamon, black pepper, ginger, red pepper and oregano in different concentrations had positive effects on the digestion and absorption of many materials with an improvement in the morphology of the gastrointestinal tract in broilers (Upadhaya et al., 2016). The positive effect of medicinal plants can be attributed to improving nutrient absorption as a result of stimulating saliva and bile secretion and increasing the effectiveness of digestive enzymes (Jag et al., 2007), leads to an improvement in the health of the bird in general. Maty and Hassan (2020) indicated that, the supplement of essential oils of thyme and activated charcoal at concentrations of 300, 600 and 900 g / ton feed to quail diets resulted in  an elevated in villi length, villi width, crypts width and surface area of ​​villi with an increased in the level of growth hormone. Kiczorowska et al. (2016) found that the addition of Boswellia Serrate at a concentration of 2 and 2.5% to a broiler diets led to a significant raise in the length of the duodenum and the gut as a whole.

Prebiotic, Probiotic and Synbiotic as feed additives

Prebiotic

Prebiotics can be defined as selective fermentable substances allowed for change in composition and activity of microorganisms in the gut of the poultry and thus improve the health of the bird (Pineiro et al., 2008). Anther definition of prebiotic that are compounds used selectively by microbiota to improved bird performance (Gibson et al., 2017). Prebiotics include various non-starch polysaccharides including mannan-oligosaccharide (MOS), malto-oligosaccharide, gluco-oligosaccharide, xylo-oligosaccharide, lactulose, lactitol, etc. Prebiotic is a specific type of nutrient fiber that is unaffected by environment condition, and stomach acids that stimulate growth (Nagpal and Kaur, 2011). The prebiotic not only induced change in the activity of the intestinal microorganisms but also diverts fluids in and into the lumen of the gut (Arturo et al., 2019). The expected mechanism of action for prebiotic includes blocking of receptor portion for bacterial adhesion, modulation of immunity, produced of antibacterial compounds, increased exudation in the lumen of the intestine in addition to the induced of morphological change in intestinal structure (Pourabedin and Zhao., 2015). The immune modulation mechanism by the prebiotic was attributed to the stimulation of humoral immunity through the interaction of sugar with specific receptors located on the roof of macrophages and dendritic cells, which subsequently induced cytokine release and lymphocyte proliferation (Saad et al., 2013). Many prebiotics needed by about 3 g / day or more to showed their action (Roberfroid et al., 2017) and any product used at a lower dose than the aforementioned was not called a prebiotic unless it is demonstrated that the lower dose showed positive effects in increased the productive characteristics of the poultry (Gibson et al., 2017). Calik and Ergün (2015) indicated that, the use of Lactulose, which is a synthetic non-digestible sugar showed prebiotic effects in broiler leading to significant improvement in body weight, nutritional conversion ratio, increased in villi length and width and goblet cell numbers. Studies have showed that oligosaccharides of mannose or fructose possess an inhibitory effect on Salmonella and E-coli (Stanly et al., 2014). There are several characteristics that must be taken into consideration when selecting prebiotic as feed additives in poultry diets, including its resistance to stomach acids, intestinal catalyzing enzymes and the ability to be absorbed through the intestinal mucosa (Pourabedin and Zhao, 2015). In addition to the importance of the prebiotic in improving the effectiveness of the poultry digestive system, the prebiotic should work to create a barrier for colonies of pathogenic bacteria such as Campylobacter and Salmonella, and the importance of the prebiotic in increasing the effectiveness of production of short-chain fatty acids against pathogens produced by food (Kim et al., 2019). Another form of prebiotics such as MOS have a direct effect as an antigen and are able to increase the immune response (Teng and Kim, 2018). In general, the prebiotic fermented by healthy bacteria in the gastrointestinal tract produced lactic acid and short chain fatty acids in addition to some anti-bacterial compounds such as bacteriocin against different types of pathogens (Lavelle et al., 2010). The production of these materials is considered beneficial not only to lose the effectiveness of the microorganisms present in the gut, but also to improve the integration of epithelial cells in the intestine and thus lead to an raise in the assimilation of digested nutrients, which results in the improvement of the productive characteristics of the bird (Lan et al., 2005). The microorganisms in the gastrointestinal tract were affected by several factors including nutrition, gender, the surrounding environment in addition to the age of the chicken, these factors can change the types of bacteria present in the intestine, for example, Clostridiaeae and Enterobacteriaceae bacteria were considered among the main bacteria present in the intestine of the bird at the age of 7 days, while Lactobacillaceae and Clostridiacea represent the main bacteria at 35 days old in the bird's intestine (Pourabedin and Zhao.,2015). Studies showed that adding MOS from 0,5 to 0,8% to poultry diets led to a changed in the contents of the cecum by increasing the numbers of anaerobic bacteria (Lactobacillus and Bifidobacterium), and reducing the amount of Salmonella, E. coli and Clostridium perfringens (Corrigan et al., 2015). MOS increased the villi length, the surface area of ​​the villi, and decreased the depth of the crypts with an raised in the numeral of goblet cell (Rajani et al., 2016).

Probiotic

The probiotic is known as a microorganism that aids the growth of other useful bacteria in the intestine that get better the microbial balance of the gut (Hill, 2014). There are different sources of the probiotic including milk and fermented foodstuffs, in addition to the possibility of commercially isolating the probiotic from the fermented compounds of Lactobacillus and Bifidobacterium (Ran et al., 2019), in addition some types of fungi including strains of yeasts pertinence to Saccharomyces cerevisiae and Kluyveromyces (Anadon et al., 2016a). One of the good characteristics of the probiotic is that withstand handling and storage operations, resistant to gastric acidity, possesses the ability to adhere to the intestinal epithelium and potential for immune modulation (Anadon et al., 2016b). Among the mechanisms possessed by the probiotic are the so-called biostimulators of the intestinal microflora by increasing the production of antibodies and reducing cell apoptosis (Khan et al., 2016). The probiotic stimulates the production of mucin in the intestine by the goblet cells, which in turn prevents pathogenic bacteria from attaching to the walls of the gut (Hardy et al., 2013). Sohail et al. (2010) indicated that, the probiotic consisting of different types of lactobacilli possesses the ability to produce multiple types of enzymes, including amylase, keratinase and β-mannanase when added to the ration of broilers exposed to heat stress, which leads to improvement of many productive performance. Hameed et al. (2020) reported that adding the probiotic formed from Saccharomyces cerevisiae to quail diets at a concentration of 0.5 g / kg of diet led to an increased in body weight, improved food conversion ratio with improvement in productive and reproductive characteristics through an increased in FSH and LH levels, AbouKassem et al. (2020) found that supplying poultry diets with B. toyonensis and B. bifidum delays the growth and reproduction of fungi in the gut. The addition of lactic acid producing bacteria as a probiotic to poultry ration increased villi length in the gut and villi width in the duodenum and improved gene code for mucin production (Ariyadi and harimurti., 2015). AbdelMoneim et al. (2019) and Abd El-Moneim et al. (2020) indicated  that supplementation of Bifidobacteria strains to an 18 day old resulted in an increased in villi length in the hatched chicks. B. subtilis strains improved the bird's health and the food conversion ratio and increased the production of IgA in the duodenum when added to the poultry diet (Amerah et al., 2013). Addition of the probiotic containing the B. licheniformis strain at a dose of 250,500,750 mg / kg ration resulted in an increased in egg production in Laying hens (Chaucheyras-Durand and Durand, 2010). Abdullah (2014) reported that adding the probiotic supplement to pigeon food at a rate of 2g / kg of feed elevated body weight, red blood cell count and hemoglobin concentration. Fig (1).

Synbiotic

Synbiotic is a combination of prebiotic with probiotic (Alloui et al., 2013). Among the types of probiotic used in synbiotic are Lacbobacilli, Bifidobacteria spp, S. boulardii, B. coagulans and others, while the prebiotic is oligosaccharides like fructooligosaccharide (FOS), xyloseoligosaccharide (XOS), inulin. The importance of synbiotic to host is to induced balance of intestinal microbiota, improved liver function and increased immune response (Zhang et al., 2010). Yitbarek et al. (2015) indicated that utilize a mixture of yeasts derived from carbohydrates with the probiotic to poultry diets led to an raised in body mass with an ameliorate on in the FCR.

External enzymes as feed additive

One of the important strategies in the poultry diet is the employ of external enzymes as nutrient supplements in their ration. There are different types of enzymes used in poultry diets, including pectinase, hemicellulase glucanase, phytase, xylanase and mannanase (Taylor-Pickard and Spring, 2008). Enzymes can be defined as biological analyzers that perform many vital functions in living organisms. It is found naturally in living organisms and is produced largely in aerobic and anaerobic cultures as well as fungi (Muhammad et al., 2010). The mode of action of these enzymes is generally summed up as follows:

1- A complete breakdown of plant cell walls containing anti-nutritional agents present in many feedstuffs used in animal diets by making a hole in the walls of these cells, allowing water and digestive enzymes to enter the interior and thus facilitate the digestion of starch and protein (Jakson et al., 2004).

2- Reducing the viscosity of digested materials as studies conducted on single stomach animals showed a decrease in the viscosity of digested materials due to enzymes that destroy non-starch polysaccharides (Cowieson et al., 2006).

3- Analyzing specific types of bonds for protein and carbohydrates, thus increasing the availability of amino acids and monosaccharaides (Meng et al., 2005).

4-Stimulating microflora colonies, as adding enzymes that destroy non-starch polysaccharides breaks down carbohydrate cell walls, reduced chain length and produced shorter chains that later become raw materials for fermentation of beneficial bacteria, Many research indicated that the addition of exogenous enzymes significantly changed volatile fatty acid production  and colonies of microflora (Cheng et al., 2014).

5- Breaking down the chemical bonds in the primary foodstuffs that are not analyzed by the gastric enzymes in the digestive system, thus providing many nutrients for other enzymatic reactions (Elijah et al., 2013).

Choct (2006) indicated the crucial function of enzymes in the digestion of many nutrients, for example amylase digests starch, protease digests protein and lipase digests fats. Poultry, including broiler lack the enzymes that digest the fiber in the grains, so it needs some external enzymes to complete the digestion of foodstuffs, as these fibers work to prevent internal enzymes from binding to nutrients and thus get hindered in the digestion and absorption process, so adding grains frequently to poultry diets hinder the digestion process, increased the activity of unwanted microbiota in the intestine, reduced metabolism and inhibited growth and the quality of meat (Muhammad et al., 2010), so, adding enzymes to poultry diets reduced these negative effects of fiber (Choct, 2006). Exogenous enzymes can break down non-starch polysaccharides in poultry that are fed sticky grains such as wheat and barley (Adebiyi et al., 2010). Preparing poultry diets with a mixture of glucanase and xylanase improved the FCR and nutrient digestion in the ileum, so, adding two types of enzymes produces a synergistic effect than if only one type of enzyme was used (Cowieson et al., 2010). Non-starch polysaccharides work by combining with water molecules in large quantities resulted in an increase in the viscosity of foodstuffs, which leads to problems in digesting carbohydrates, proteins and fats in the small intestine, the anti-nutrient  effect of these sugars works to impede growth and food conversion ratio(Kalantra et al., 2017). Improving the digestion of nutrients by enzymes was by reducing the excretion of beneficial compounds, especially nitrogen, phosphorous, zinc and copper (Abd El-Hack et al., 2017). When adding enzymes to poultry diets that contain a high percentage of high-fiber soybeans, it stimulated the digestive process and reduced the harmful effect of fiber (Alagawany et al., 2015). Enzymes also increased the energy level and protein digestion of broilers (Pourreza et al., 2007). The xylenase enzyme reduced the competition of pathogenic bacteria with intestinal microorganisms for food sources and this provided many beneficial nutrients to the bird (Hosseini and Afshar, 2017).

External emulsifiers as feed additive

The use of animal fats and vegetable oils has become an important strategy in poultry diets, especially in broiler, for the purpose of improving the growth rate and the food conversion ratio as a result of the high energy resulting from the assimilation of fats (Zhang et al., 2011). An emulsifier is defined as a mixture of two or more liquid substances that usually cannot be mixed together in which one of the liquids is scattered or widely diffused in the other liquid, and it is also known as a molecule with a hydrophilic and lipophilic part having this property in one molecule It gives it unique properties so that the emulsion can dissolve in fat and water and help mix these two parts (Siyla et al., 2017). Emulsifiers that are used naturally in the food industry are classified into two groups, the first is called natural emulsifiers such as bile salts, and the second is nutrient emulsifiers such as lecithin and Lysolecithin. The emulsification process rely on the nature of the fats and is mainly determined by the length of the chain, the location of phospholipids in triglycerides and the degree of saturation of fats (Gu and Li., 2003). The digestion of fats is complicated and required adequate amounts of bile salts and the lipase enzyme, which are essential for fat emulsification (Ravindran et al., 2016). The difficulty in digesting fats comes as it occur in the aquatic surroundings of the digestive system even though they are insoluble compounds in water and lipid assimilation was limited in young birds because of their reduced ability to make and excrete bile salts and the lipase till the digestive system matures in birds of age (10-14) day (Upadhaya et al., 2018). Several studies indicated that the supplement of external emulsifiers in the poultry diet improves fat digestion, growth rate and production (Zafarian et al., 2015; Zhao et al., 2015). There were many form of external emulsifiers that are used in chicken diets, including sodiumstearoy l-2-lactylate (SSL), 1,3-Diacylglycerol, lysophospholipids, lysophosphatidylcholine, soybean oil, lecithin and Lysolecithin (Upadhaya et al., 2016). Tancharoenrat et al. (2013) also indicated that poultry showed the best growth and weight gain during the growth phase when adding vegetable oils to their diets, Kamran (2020) also indicated that using different types of fats and oils to broiler diets such as polyglycerol polyricinoleate and soybean oil at a dose of 0.25% and 0.45%, respectively, improved the digestion of fats and the food conversion ratio with an increase in body weight. Emulsifiers increased the stimulation of micelles, increased the monoglycerid in the gut, expedited the transmit of nutrients through the walls of the intestine and allow for better absorption of digested substances and the preparation of energy (Roy et al., 2010). Emulsifiers also facilitated the process of shunting of fats and reduced their deposition in the liver, improved the absorption of calcium and phosphorus, it reduced the excretion of fats and increased the digestion of fats in the ileum (Dierick and Decuypere, 2004). The addition of fats to poultry diets was of great importance as it played an remarkable role in the assimilation of fat-soluble vitamins through their function as carriers (Iqdal and Hussain, 2009). The mechanism of action of food emulsifiers was to digest fats in three ways which is the formation of emulsion droplets, stimulating the formation of micelles, which are a complex of lipids-bile salts, and increasing the rate of monoglycerid in the intestine, this emulsification property allowed providing a greater surface area for the lipase to work more efficiently (Roy et al., 2010). Siyal et al. (2017) indicated that adding lecithin to the diets of broiler at a dose of 0.05% led to a declined in the level of cholesterol and LDL in the blood serum and a reduction of stress by lowering the level of MDA and thus improving the body weight and food conversion ratio in broilers. As mentioned by Aleksander et al. (2019) that adding external emulsifiers at concentrations of 250, 500 ppm to turkey diets from the age of 8 weeks to 16 weeks led to increased growth and improved fat digestion, so adding external emulsifiers to poultry diets has great importance in improving the characteristics bird productivity.

CONCLUSION

This article concludes that the use of feed additives as alternatives to antibiotics has a very important effect in improving the productive traits of birds due to their antibacterial properties, antioxidant and growth stimulator in addition to their importance to induce morphological changes in the structure of the gastrointestinal tract.

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