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Immunomodulatory efficacy of yeast cell products in poultry: a current review

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The changes in immune functions of birds, obtained during the decades of intensive selection, are rather disadvantageous. Today’s chickens and turkeys are more susceptible to different infectious and metabolic disease and exhibit a high mortality
  10.1017/S0043933913000… 1 Immunomodulatory efficacy of yeast cell 2 products in poultry: a current review 3 S. Ś WI Ą TKIEWICZ 1 *, A. ARCZEWSKA-WŁOSEK 1  and D. JÓZEFIAK 2   4 1 National Research Institute of Animal Production, Department of Animal 5 Nutrition and Feed Science, ul. Krakowska 1, 32-083 Balice, Poland; 2 Pozna ń   6 University of Life Sciences, Department of Animal Nutrition and Feed 7 Management Woły ń ska 33, 60-637 Pozna ń , Poland 8 *Corresponding author: 9 Yeast products and immune response: S. Ś wi ą tkiewicz et al. 10 © World’s Poultry Science Association 2014 11 World’s Poultry Science Journal, Vol. 70, March 2014 12 Received for publication January 29, 2013 13 Accepted for publication July 17, 2013 14 The changes in the immune function of birds obtained during decades of intensive 15 selection are rather disadvantageous. Today’s chickens and turkeys are more 16 susceptible to different infectious and metabolic diseases and exhibit a high 17 mortality rate. Subsequently in recent years there is growing interest in the use of 18 feed additives with immunomodulatory properties in intensive poultry production. 19 This article reviews and discusses the results of current studies on the effects of 20 yeast cell products on the different mechanisms of the immune system in poultry. 21 The majority of the experiments presented in this review indicate that the use of 22 yeast derivatives may have a beneficial influence on the immune system and 23 resistance to the colonization of pathogenic microorganisms. However, the positive 24 effect of yeast derivatives on the immune system is not always reflected in an 25 improvement in production parameters, especially when the experiments are 26 conducted on healthy (non-challenged) birds. 27 Keywords:  poultry; nutritional immunomodulation; yeast cell; mannanoligosaccharides; 28 β -glucan; innate response; acquired response 29 Introduction 30 Over the last few decades genetic selection for performance traits ( e.g.  rapid growth) has 31 been performed intensively and together with this there has been intensification in 32 poultry production. It has been found that this can adversely affect the immune function 33 and decrease the natural resistance of birds to pathogenic factors and infections (Li et al ., 34 1999; Kramer et al ., 2003; Huff et al ., 2005). For example if the immunocompetence of 35 fast-growing, commercial broilers and a line of chickens that have not been subjected to 36 selection are compared, it can be found that the long-term genetic selection for improved 37 performance has negatively affected the adaptive form of the immune response, i.e.  38  antibody production against sheep red blood cells (SRBC), but increased cell-mediated 39 and inflammatory responses. These are less effective for combating bacterial diseases 40 and are often unfavourable for feed intake and performance indices (Cheema et al ., 41 2003). 42 Results of a study by Genovese et al . (2006) showed that oxidative burst and 43 degranulation activities on days four and seven post-hatch in a modern line of turkeys 44 were significantly lower compared to a wild type line. Subsequently the authors 45 suggested that a fast growing, modern turkey can be at an immunological disadvantage 46 during the first days post-hatch. Results of recent meta-analysis of data from different 47 poultry studies has proven that selection for rapid growth has strongly reduced the 48 response to a variety of immune challenges and may unintentionally have resulted in 49 poor immune function (Van der Most et al. , 2011). 50 One of the most important factors essential for effective immune function is appropriate 51 nutrition, i.e.  supplying the animal with the optimal amount of digestible nutrients. 52 Nutritional deficiencies can have an adverse effect on the development of lymphoid 53 organs, the synthesis of immunologically active substances, and the proliferation of 54 lymphocytes and their phagocytic activity (Klasing, 1998; Kidd, 2004), in this way 55 decreasing the resistance of animals to pathogenic microorganisms. It is known that the 56 requirement for some nutrients to achieve optimal immune function can be higher than 57 for obtaining maximal performance (Rama Rao et al ., 2003; Biswas et al. , 2006; 58 Klasing, 2007). The most important nutrients for the immune system are: amino acids 59 (arginine, methionine), vitamins E, A and C, microelements (Zn and Se) and long chain 60 polyunsaturated n-3 fatty acids. 61 After the removal of the sub-therapeutic use of antibiotic growth promoters (AGP) from 62 animal nutrition in the European Union, due to fear of the appearance of antibiotic-63 resistant microbes in human health, the interest in natural feed additives with 64 immunomodulatory properties have increased significantly. This interest in nutritional 65 immunomodulators is particularly meaningful in conditions of intensive poultry 66 production, where many stressful factors, for instance high stocking density, have a 67 negative influence on animal health. Nutritional immunomodulation may be defined as 68 diet supplementation with specific nutrients or activities to affect some effective aspects 69 of immune function in order to achieve an intended goal (Korver, 2012), i.e.  the effective 70 work of the immune system and the resistance of the organism to viral, bacterial and 71 protozoa infections. Mechanisms which are involved in the animal’s immune system can 72 recognise chemical structures that are typical for potentially harmful microorganisms 73 and play the role of a specific ‘emergency signal’ to starting an immunological response 74 protecting against infection. Therefore, potential nutritional immunomodulators should 75 contain such chemical structures that are able to activate immune system responses. 76 Scientific findings of some recently published papers indicate that different yeast 77 derivatives can have particularly promising immunomodulatory properties. Therefore, 78 the aim of this article is to review and discuss the results of the current poultry studies 79 where immunomodulatory characteristics of yeast cell products and their effects on 80 bird’s immune functions were determined. 81 Properties of yeast cell products 82 Dried yeasts have been used in animal nutrition for many years, mainly as a rich source 83 of good quality proteins and B vitamins. More recently, yeast cell products, obtained 84 from different yeast strains (mainly from Saccharomyces cerevisiae) , have been used as 85   zootechnical feed additives . They are derived from the yeast’s cell wall or the inside of 86 the cell, after removal of the cell wall, as different extracts. Although the composition 87 and content of the active substance in different yeast products are variable, they usually 88 contain such compounds with potentially immunomodulatory properties as: β -1.3/1.6-89 glucans, mannan oligosaccharides (MOS), nucleotides, inositol and glutamine. 90 Yeast’s β -1.3/1.6-glucans are long-chain polysaccharides, comprising numerous D-91 glucose monomers linked by β -glycosidic 1.3 bonds that represent about 85% of cell 92 wall β -glucan, with side-chains of D-glucose attached at the 1.6 position (Kollar et al ., 93 1997). Such specific composition of yeast β -1.3/1.6-glucan is different from the structure 94 of cereal’s β -glucan (1.3/1.4) and is responsible for its great biological activity, wherein 95 immunomodulatory properties of β -glucan are connected with the presence of β -1.3 96 bonds. β -1.3/1.6-glucans can bind to macrophage-specific CR3 receptors by recognition 97 of specific sugars found in glycoproteins of the epithelial surface, triggering a cascading 98 reaction that activates macrophages to phagocytosis, and to the production of cytokines 99 and eicasonoids, such as IL-1, TNF- α  and PGE2 (Doita et al ., 1991; Abel and Czop, 100 1992) activating, in this way, the proliferation of lymphocytes, both CD4+ and CD8+, 101 that results in an increase of both innate and acquired (cell-mediated and humoral) 102 immune response. 103 The most known property of mannan oligosaccharides (MOS), derived from yeast cell 104 wall, is their ability to agglutination of gram-negative pathogenic bacteria containing 105 type 1 fimbriae (mannose binding lectins), for instance Salmonella sp. and  Escherichia 106 coli . These pathogens can be adsorbed to the MOS instead of attaching to intestinal 107 epithelial cells and move through the intestine without colonization (Ferket et al. , 2002). 108 However, there is evidence that MOS can act as a nonpathogenic antigen, which may 109 have adjuvant-like activity and beneficially modulate the host immune function. This 110 immunomodulatory effect of MOS can be attributed to the presence on the surface of a 111 variety of defence cells of mannose receptors that are involved in antigen recognition 112 (Engering et al ., 1997). 113 Yeast cell extracts are an important source of nucleotides from the yeast’s RNA, which 114 are involved in many biological processes; among others they are the precursors of 115 nucleic acids. The immunomodulatory effects of nucleotides on different types of 116 immune response have been confirmed in numerous in vitro  and in vivo  model 117 experiments on different laboratory animals (Carver, 1994; Gil, 2002). For instance, 118 nucleotide supplementation to immunosuppressed mice infected with Cryptosporidium 119  parvum  enhanced concavalin A and antigen-specific induced spleen cell proliferation, 120 the production of cytokines IL-2 and IFN-gamma, increased the survival rate and 121 reduced oocysts excretion (Adjei et al ., 1999). The mechanism of action of nucleotides 122 on immunity is not completely understood, but probably can be connected with the fact 123 that rapidly proliferating tissues of the immune system may not be able to fulfil the 124 requirements of nucleotides exclusively by de novo  synthesis and salvage, and they 125 preferentially utilise nucleotides and nucleobases from blood and diet (Carver, 1994; Gil, 126 2002). 127 The effects of yeast products on immunity in poultry 128 TURKEYS  129 One of the first and most cited reports on the immunomodulatory effects of yeast 130 products in poultry was published in 1996 and concerned turkey diet supplementation 131 with MOS (Savage et al ., 1996a; 1996b). In this study significant stimulatory effects of 132  MOS (1.1 g/kg of diet) on plasma IgG and bile IgA antibody levels, body weight gain 133 and intestinal villus height in turkey poults were reported. Similarly, in the subsequent 134 experiment dietary MOS supplementation (1 g/kg) increased serum IgG and IgM levels 135 and decreased T lymphocyte percentage in the peripheral blood (Cetin et al ., 2005). 136 Huff et al . (2010) evaluated the ability of commercial yeast extract product (YE, 137 Alphamune) to modulate the immune response in male turkey poults challenged with  E. 138 coli . In this experiment the numbers and percentages of heterophils in peripheral blood 139 were increased and their oxidative burst activity was stimulated by YE. As an effect of 140 these changes in the innate (non-specific) immune response,  E. coli bacteria were 141 isolated from the air sac and liver of a lower percentage of birds provided with YE. Diet 142 supplementation with YE also had a positive effect on blood haematology. In addition, 143 YE modulated the dramatic increase in oxidative burst and serum triglycerides due to 144 transport stress. In conclusion, the authors suggested that YE, due to its 145 immunomodulatory properties, has potential as a non-antibiotic alternative for 146 decreasing pathogenic bacteria in turkey production (Huff et al ., 2010). These same 147 authors (Huff et al ., 2011) indicated that YE can positively modulate an innate immune 148 response, measured as the heterophyle oxidative burst activity, improve the body weight 149 gain at the first week of age and decrease the mortality in stressed female turkeys. There 150 was also a tendency for increased heterophyle/lymphocyte ratio after diet 151 supplementation with YE due, the authors suggested, to the fact that yeast may function 152 as a mild stressor, which enables the animal to adapt more easily to other stressors (Huff 153 et al ., 2011). 154 BROILER CHICKENS  155 The effects of yeast product supplementation were studied in broiler chickens by Gao et 156 al . (2008). They found that yeast culture (Diamond V XP Yeast Culture) positively 157 modified immune functions, both the innate and acquired immune response. As part of 158 innate immunity, the activity of serum lysozyme was increased, which suggested that 159 more phagocytes were activated and better protection against infections was provided 160 when the yeast culture was added to the diet. As part of an acquired, humoral immune 161 response, enhanced antibody titres to Newcastle disease virus and serum IgM were 162 reported. Likewise, the mucosal immunity, measured as a secretary IgA concentration in 163 the duodenum, was increased in broilers fed the diet supplemented with yeast culture. It 164 should also be noted that yeast product, used in this experiment at 2.5 g/kg, significantly 165 improved body weight gain, feed conversion, digestibility of Ca, P and energy, retention 166 of protein, and villus height to crypt depth ratio in the duodenum, jejunum and ileum 167 (Gao  et al ., 2008). 168 In a subsequent study, the above authors evaluated the immunostimulative efficacy of 169 the Saccharomyces cerevisiae  fermentation product in  Eimeria tenella -infected broilers 170 (Gao  et al ., 2009). They reported that body weight gains were significantly decreased by 171 coccidial infection and improved by yeast supplementation. The positive effect of yeast 172 product on immune response was reflected in increased CD3+, CD4+ and CD8+ T-173 lymphocyte counts, the ratio CD4+/CD8+ in blood and the spleen, and ileum 174 intraepithelial lymphocyte count and caecal tonsil secretory IgA counts. The authors 175 concluded that the yeast product used could improve the immune function and growth 176 performance in coccidia-infected chickens (Gao  et al ., 2009). The beneficial effects of 177 whole yeast cell product, in chickens challenged with  Eimeria  sp. were confirmed 178 recently by Shanmugasundaram et al.  (2013). They reported that whole yeast cell 179 product significantly increased macrophage nitric oxide and inflammatory cytokine 180  production, improved body weight gain and feed efficiency, and decreased the faecal 181 coccidial oocyst count during postcoccidial challenge. 182 Interesting results were obtained when yeast ( Saccharomyces cerevisiae ) products, i.e.  183 yeast cells, yeast protein concentrate (YPC) or YPC-pellets, were added to the diet (1 184 g/kg) of heat-stressed broilers orally challenged with Salmonella enteritidis (Haldar et 185 al ., 2011). Humoral immune response against Newcastle disease was significantly 186 increased by YPC and YPC-pellets at 14d, 28d and 35d, and yeast cells 187 supplementation at 35d of age. These beneficial, immunomodulatory effects of YPC 188 and YPC pellets were confirmed by a significant improvement of performance indices, 189 i.e.  body weight at 21 and 35d and FCR in 35d. Yeast products, mainly YPC and YPC-190 pellets, were also effective in a decreasing of Salmonella  numbers in digesta and excreta 191 and  E. coli  numbers in digesta, reducing of serum cortisol and increasing of serum T3 192 concentration (Haldar et al ., 2011). 193 The positive effects of yeast on the immune functions of broilers were found when the 194 yeast cell wall (YCW) was evaluated. Thus, a dietary addition of YCW derivative 195 containing 25% MOS and 30% β -glucan enhanced innate immunity response, measured 196 as phagocytic activity of macrophages, in chickens inoculated with Sephadex G-50 197 (Ferreira et al ., 2011). Macrophages are not only the elements of innate immunity, where 198 they destroy bacteria by phagocytosis but, by secretion of cytokines and presentation of 199 antigens, they are also important for acquired (specific) immune response. However, in 200 the study of Ferreira et al . (2011), the response in immunity was found at one level of 201 YCW product addition (2 g/kg of diet) and did not beneficially affect the performance 202 parameters of chickens. Recently the efficacy of Saccharomyces cerevisiae  YCW dietary 203 supplementation for protecting the integrity of intestinal mucosa in broilers vaccinated 204 against coccidiosis was evaluated (Luquetti et al ., 2012). It was found that the villi of 205 birds supplemented with yeast cell (2 g/kg) wall were higher, irrespective of a 206 vaccination against coccidiosis. When YCW was added to the diet of vaccinated 207 chickens, a slight reduction in epithelial cell loss percentage was noted. The authors 208 concluded that S. cerevisiae  YCW supplementation may be a useful management tool to 209 maintain the intestinal integrity of broilers vaccinated against coccidiosis (Luquetti et al ., 210 2012). Results of the study of Ghosh et al . (2012) revealed that YCW can provide 211 greater immunity against Newcastle disease than AGP (bacitracin methylene disalicyte), 212 may ensure greater protection against intestinal colonization by Salmonella pullorum  213 bacteria, and improve feed efficiency (Ghosh et al ., 2012). 214 Zhang et al.  (2012) determined the effects of dietary YCW ( Saccharomyces cerevisiae ) 215 on the performance and immune function of cyclosporine A-treated (immunosuppressed) 216 chickens. The results showed that supplementation of YCW (3 g/kg) significantly 217 improved daily weight gain compared with the control. YCW significantly mitigated the 218 cyclosporine A-induced decrease of peripheral blood lymphocyte blastogenic response. 219 In addition, YCW significantly increased the relative weights of the bursa of Fabricius 220 and thymus, and up-regulated the splenic expression of pro-inflammatory cytokines IL-221 1 β  and IL-6 in immunosuppressed birds. The authors indicated that YCW has a 222 beneficial influence in attenuating the immunosuppressive effects of cyclosporine. The 223 challenge, therefore, is improving the growth performance of broiler chickens (Zhang et 224 al. , 2012). Similar results were found in the study of Muthusamy et al.  (2011), where 225 YCW positively affected body weight gain, feed conversion and villus height in the 226  jejunum, and enhanced humoral immune response, measured as antibody level, against 227 the Newcastle disease vaccine (NDV). It was also reported that YCW supplementation 228 (2 g/kg) could mitigate the negative effect of Fusarium  mycotoxins on the immune 229
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