1Department of Animal Science, Faculty of Agriculture and Natural Resources, Science and Research Branch, Islamic Azad University, Tehran, Iran
2Department of Animal Science, Karaj Branch, Islamic Azad University, Karaj, Iran
3Department of Animal Science, Faculty of Agricultural Science, University of Guilan, Rasht, Iran
4Department of Animal Science, Faculty of Agriculture and Natural Resources, University of Tehran, Karaj, Iran
5Department of Animal Science, Saveh Branch, Islamic Azad University, Saveh, Iran
Receive Date: 20 February 2016,
Revise Date: 29 March 2016,
Accept Date: 15 April 2016
A feeding trial with twenty-seven male weaned Zandi lambs (initial body weight 27.1±0.38 kg) was conducted to evaluate the effect of different levels of Saccharomyces cerevisiae SC47 in diet containing high concentrate (85%) on the growth performance, blood parameters and immune system status. Lambs were allocated to one of three treatment diets in a completely randomized design with 3 replicates and 3 observations per replicate including: 1) basal diet without yeast, control diet; (CD) 2) basal diet with 3 g yeast per lambper day, low yeast; (LY) and 3) basal diet supplemented with 4.5 g yeast per lambper day, high yeast; (HY). Regarding dry matter intake (DMI), there was no significant difference among treatments (P>0.05). Average daily gain (ADG) was greater in HY group, but differences among treatments were not significant (P>0.05). Feed conversion ratio (FCR) was not significantly affected by dietary treatments (P>0.05). Differences between concentrations of total protein, globulin and albumin/globulin ratio (A/G) were significant (P<0.05). The highest amount of total protein and globulin was observed in LY group (P>0.05). Lambs in CD group had the highest amount of A/G ratio. No significant differences were found for the hematology results (P>0.05). No significant differences were detected in differential white blood cells, except neutrophil band that was greater in HY group at the twelfth week (P<0.05).It is concluded that the use of dietary live yeast in high concentration can improve performance (P>0.05), plasma biochemical metabolites(P<0.05) and hematological parameters (P>0.05) in Zandi lambs.
Different feed additives were added to animal’s diet with the aim of increase breeding, health and quality of products in animal breeding for a long time. For several years antibiotics were the most important feed additives that was used, but in the last decade, the use of antibiotics in animal husbandry is in question, due to the development of antibiotic resistance. Research shows an association between the use of subtherapeutic dose of antibiotics and antibiotic resistance in organisms (Amabile-Cuevas et al. 1995). In an effort to replace antibiotics in animal feeds, many additives have been proposed. Recently, alternatives for substituting these traditional growth promoters have been evaluated, probiotics, prebiotics and ionophores are examples of these promoters (Heinrichs et al. 2003). The probiotics are classically defined as live microbial dietary supplements that when administered through the digestive tract, cause a positive impact on the host’s health by improving gut micro flora (FAO, 2002; Salminen et al. 1996; Fuller, 1989). Studies on the beneficial impact of probiotics on animal performance have indicated that probiotic supplementation could have positive effects (Miles et al. 1981). One of the most common probiotics in ruminants, are Saccharomyces cerevisiaeyeast (SC). The use of SC as a probiotic, began during the 1940’s and 1950’s (Beeson and Perry, 1952). Live yeast consumes free oxygen in the rumen with respiration, so provides an anaerobic environment that proper for rumen metabolic function (Newbold et al. 1995). Enzymes, vitamins, saccharides [β-glucans (βGs) and mannan oligosaccharides (MOSs)] found in yeast cell walls have immunomodulative properties. MOSs are capable of neutralizing pathogenic bacteria, and they support βGs in the process of stimulating defense mechanisms (Małaczewska and Milewski, 2010). Other metabolites produced from yeast fermentation may have benefit on performance and health of animals. The main target of using yeast for growing lamb is to increase the breakdown of dietary fiber and protein that lead to increase microbial protein as a main source of amino acids in the small intestinal, consequently, improve growth. Moreover, SC yeast has biologically valuable proteins, vitamin B-complex, important trace minerals and several unique plus factors. Many other beneficial effects identified such as improve performance (Glade and Sist, 1988; Martin et al. 1989) and feed efficiency (Onifade and Babatunde, 1996), affects on ruminal pH by reducing activity of lactic acid producer bacteria and thus reduce ruminal acidosis and metabolic disorders (Williams, 1989; Guedes et al. 2008; Thrune et al. 2009), enhance the immune response (Keyser et al. 2007), ability to enhancement of phosphorus availability (Glade and Biesik, 1986; Brake, 1991; Moore et al. 1994) and utilization by animals (Erdman, 1989; Pagan, 1990), reduction in cases of disease infection (Line et al. 1997). However, the results of using the SC in ruminants are contradictory because of this fact that in many cases no influence or opposing and many unclear results have been shown (Masek et al. 2007). The lack of positive results: (Mikulec et al. 2010), can be related to biotic factors such as amount and yeast viability and to abiotic factors such as diet sources and animal management (Sales, 2011). One of the most important reasons for such inconsistent results is diet composition. Young animals with high growth potential, need the diets with high protein and energy content according to (NRC, 1985), which can hardly be achieved in an exclusive forage diet. So, to obtain high performance, they should be fed with a high proportion of concentrate diets. Yeasts are most efficient when animals are fed diets overloaded in energy and thus easily fermented by rumen microorganisms (Williams et al. 1991) or diets poor in nutrient supply (Jouany et al. 1998). Consumption of large amounts of readily fermentable carbohydrates can change the rumen fermentation pattern. This function can increase production of short chain fatty acidsand lactate, and decrease pH, which affect the amounts of cellulolytic bacteria and reduces fiber digestibility and the production of microbial mass (Mackie et al. 2002). Therefore, it is necessary to control fermentation and use additives to maintain rumen health and improve animal production. So, the objective of current study was to investigate the effect of different levels of live yeast SC47 in diet containing high concentrate (85%) on the growth performance, blood constituents and immune system status of Zandi lambs.
MATERIALS AND METHODS
Animals, diets and experimental design
Feeding trial with twenty-seven male weaned Zandi lambs (initial body weight 27.1±0.38 kg and 90±5 days-old), that were grouped based on body weight, were conducted to evaluate the effect of different levels of Saccharomyces cerevisiae SC47 (biosaf probiotic) in supplemental diet on the growth performance, blood constituents and immune system status. Lambs were grouped based on body weight, ear tagged and vaccinated against internal and external parasites, and were allocated to one of three dietary treatments in a completely randomized design with 3 replicates and 3 observations per replicate including: 1) basal diet without yeast, control diet; (CD) 2) basal diet with 3 g yeast per lambper day, low yeast; (LY) and 3) basal diet supplemented with 4.5 g yeast per lambper day, high yeast; (HY). Basal diet was consisted of commercial concentrate and hays. Ingredients and chemical composition of basal diet according to the dietary nutrient requirements for lambs (NRC, 1985) are provided in Table 1. The lambs were adapted to feed about 2 weeks. During these 2 weeks, feed intake was restricted to 3.5% of body weight (BW), based on the average BW within a pen, to allow animals to adapt to the change in diet and to prevent the occurrence of digestive disorders. After the adaption period to the end of experiments (twelve weeks), they were fed three times a day (7:00 a.m., 13:00 p.m. and 19:00 p.m.) with a total mixed ration (TMR) diet. Each pen had an automatic water cup so they had free access to water all times.
Sampling, measurement and analyses
Food intake was measured daily (before the morning feeding) and DMI was calculated.
Table 1 Ingredients and chemical composition of basal diet
1 Hays approximately chopped into particles of 3 cm.
This value was expressed as grams DMI per day (g/day). Lambs live weight was measured at the beginning of the experiment and every two weeks interval (before the first meal) and ADG was calculated. This value was expressed as grams ADG per day (g/day). Blood samples were collected at the days of 0, 42 and 84, at 10:00 h, through jugular vein (10 mL into sterile tubes containing ethylenediaminetetraacetic acid (EDTA) solution) and analyzed for concentration of plasma biochemical indicators (total protein, albumin, globulin, A/G ratio, blood urea nitrogen (BUN) and cholesterol), hematological parameters [white blood cells (WBC), red blood cells (RBC), hemoglobin (Hb), platelets (PLT) and differential white blood cells].
Data were analyzed by the general linear model (GLM) procedure of the Statistical Analysis System software (SAS, 1997), in a completely randomized design with three treatments and three replicates. The shapiro-wilk and kolmogorov-smirnov tests were used to confirm normal distribution of data. Initial body weight and the first series of each parameters of concentration of plasma biochemical indicators, hematological parameters (blood cellular elements) and differential white blood cells, were used as a covariant. Means were obtained by LSMEANS procedures and PDIFF was used to compare means. Effects between the control and experimental groups were considered significant when (P<0.05) and finally results were presented as least square means with standard error of the means (SEM).
RESULTS AND DISCUSSION
Least square means and SEM for effect of different levels of yeast supplement on performance of Zandi lambs are presented in Table 2. Considering DMI, there was no significant differences among the dietary treatments (P>0.05). So we can conclude that, live yeast (Saccharomyces cerevisiae SC47) has no significant effect on feed intake and appetite, and this may explain the lack of effect for the average daily gain and feed conversion ratio, because the dry matter intake and available nutrients concentration in food, determine the amount of nutrients used to meet demands for maintenance and production. In agreement with our results, other authors also did not find any improvement in DMI after yeast addition to lamb diets (Mikulec et al. 2010; Hernandez et al. 2009). But in some study an increase in dry matter intake was observed when yeast was fed to bulls (Galina et al. 2006) and lambs (Desnoyers et al. 2009; Rezaeian, 2004). Average daily gain was greater in HY group compared to the others throughout the experiment, but the differencewas notstatistically significant (P>0.05). Similar to the results of our study, Mandour et al. (2009) and Antunovic et al. (2006) reported higher, but not significant, ADG for lambs fed diet enriched with probiotics. In contrast, Milewski et al. (2009) and Ding et al. (2008) reported higher ADG in fatting lambs fed diet enriched with probiotics. Feed conversion ratio was not significantly affected by treatments (P>0.05), but at the end of trial, lambs in group HY consistence with ADG had the best total FCR. In Agreement with our results, some of authors also did not find any improvement in FCR after yeast addition to lamb diets (Khalid et al. 2011; Mikulec et al. 2010). In contrast to our results, Ding et al. (2008) and Masek et al. (2007) reported better FCR in fatting lambs fed diet enriched with probiotics.
Plasma biochemical indicators
Results of different levels of yeast supplement on concentration of plasma biochemical indicators of Zandi lambs are presented in Table 3. Except for total protein in the twelfth week, for the other periods the highest and lowest amounts of total protein and globulin was observed in LY and CD groups, respectively (P<0.05). In general, sub-acute acidosis can cause intestinal inflammation in animals that this situation will have a negative effect on the digestion and absorption, which one of the consequences is impaired digestion and absorption of protein and thus reduction in plasma total protein.
Table 2 Effect of different levels of yeast supplement on performance of Zandi lambs
DMI: dry matter intake; ADG: average daily gain AND FCR: feed conversion ratio.
SEM: standard error of the means.
Table 3 Effect of different levels of yeast supplement on concentration of plasma biochemical indicators of Zandi lambs
A/G ratio: albumin/globulin and BUN: blood urea nitrogen.
SEM: standard error of the means.
The means within the same row with at least one common letter, do not have significant difference (P>0.05).
The results showed that the yeast had no significant effect on plasma albumin (P>0.05) concentrations. Lambs in CD group had the highest A/G ratio and BUN, while the lowest amounts of these plasma biochemical indicators were seen in groups supplemented with yeast. Low but not significant concentrations of BUN in response to probiotic supplements can be due to increase ability of the rumen microflora in trapping ammonia (Abo El-Nor and Kholif, 1998). BUN is an indicator of the protein status in ruminants (Sykes, 1978) and its concentration is related to the level of ammonia absorption from the rumen and the deamination of amino acids not deposited in the tissues (Deaville and Galbraith, 1992). Another possibility for the lower BUN concentration is that additives promote the utilization and deposition of nitrogen in tissues. No significant differences were detected in cholesterol levels between the different groups (P>0.05). Probiotics that can reduce the intestinal pH, could contribute to the regulation of serum cholesterol concentrations by its relationship with bile acids. In the acidic conditions of the intestine, because of the inability to re-absorption of bile acids at the end of intestine, excretion of bile acids is enhanced and therefore serum cholesterol, as a precursor of bile acids, used to rebuild the bile (De Smet et al. 1994). Since in the current study Saccharomyces cerevisiae SC47 did not reduce the intestinal pH, we did not found any significant differences in serum cholesterol levels between the different groups. In agreement with our results, other authors reported similar results for some concentration of plasma biochemical indicators after yeast addition to lamb diets (Khalid et al. 2011; Mukhtar et al. 2010; Bruno et al. 2009; Masek et al. 2008).
Hematological parameters and differential WBC
Results of different levels of yeast supplement on concentration of hematological parameters and differential WBC of Zandi lambs are presented in Tables 4 and 5, respectively. Overall no significant effects were recorded on the hematology results (P>0.05). However, the highest amount of WBC was seen in yeast-supplemented groups (P>0.05). There was an increase in values for hemoglobin in LY and HY groups at the twelfth week (P>0.05). Probiotics can reproduce and develop in the gut wall as a living cell, or can capture antigens released by dead microorganisms, and by different ways, stimulate the immune system and its components (Fuller, 1977). Live yeast did not modify value of RBC and PLT in the experiments and we observed only a slight increase in RBC in group HY at the end of trial (P>0.05). No significant differences were detected in differential white blood cells, except neutrophil band that was greater in HY group at the twelfth week (P<0.05). Probiotics can stimulate and strengthen the immune system by increase of macrophage activity, which this act appears by increasing the ability of phagocytosis of microorganisms. One of this phagocytosis of organisms is neutrophil, that increase in the number of neutrophils band, in response to supplementation of probiotic, can be stimulated macrophage activity (Tizard, 2008; Fuller, 1992).
Table 4 Effect of different levels of yeast supplement on hematological parameter (blood cellular elements) of Zandi lambs
WBC: white blood cells; RBC: red blood cells; Hb: hemoglobin and PLT: platelets.
SEM: standard error of the means.
The means within the same row with at least one common letter, do not have significant difference (P>0.05).
Table 5 Effect of different levels of yeast supplement on differential white blood cells of Zandi lambs
SEM: standard error of the means.
The means within the same row with at least one common letter, do not have significant difference (P>0.05).
The immune stimulating effect of SC was ascribed to the activity of βGs and MOs presented in yeast cell walls (Milewski et al. 2007). This mechanism involves the stimulation of immune competent cells, mainly by βGs (Xiao et al. 2004; Siwicki et al. 2004). βGs activate intercellular defense mechanisms where macrophages, T-cells and NK cells play the key role (Demir et al. 2007). The specific ability of MOs to bind selected pathogenic microbes has a profound effect on the organism’s health status. MOs blocks microbial lectins and prevent pathogens from colonizing the host’s gastrointestinal system (Sharon, 2008). MOs are not degraded by the digestive enzymes of the small intestine, therefore, the attached pathogens are more easily excreted (Spring et al. 2000). In this study, where the experiment was conducted, was cleared from contamination and infection and the possibility of create any stress for the lambs was the lowest rate, that it could be one of the factors of lack of response expected for health and immune system. In agreement with our results, Mohamadi and Dabiri (2012) reported that WBC and differential white blood cells (neutrophil, monocyte and lymphocyte) were unaffected by probiotic, prebiotic and synbiotic in Holstein female calves (P>0.05). Mandour et al. (2009) reported that WBC, RBC, neutrophil, lymphocyte, hemoglobin and albumin were unaffected by bio-nutra probiotics in Awassi, Najdi and Najdi crossbred male weanded lambs (P>0.05) and Shim (2005) reported too that, hematological traits (WBC count, neutrophil, monocyte, lymphocyte and hemoglobin) were unaffected by prebiotic, multi-strain probiotic and synbiotic in weaned pigs (P>0.05). In contrast, the results of experiments conducted on suckling lambs (Milewski et al. 2009) and cattle (Dobicki et al. 2005; Dobicki et al. 2007) indicate that yeast preparations have a favorable effect on the animals immune system and values of WBC, Hb and lymphocyte were affected by yeast (P<0.05). Onifade et al. (1999) and Onifade (1997) reported a positive correlation between dietary levels of SC with the hematological parameters like WBC, RBC andhematocrit or packed cell volume (PCV) in rabbit and broiler chickens. They suggested that theses correlations may be an additional mechanism growth promotion by supplemental yeast. Recent studies indicated that yeast components may interact with immune systems and triggering immune responses (Muchmore et al. 1990; Davis et al. 2004).
In the present study, the use of live yeast (Saccharomyces cerevisiae SC47) in diet containing high concentrate could improve performance (whit not significantly different, (P>0.05)), concentration of plasma biochemical indicators (whit significantly different, (P<0.05)) and hematological parameters (whit not significantly different, (P>0.05)) of Zandi lambs. Greater ADG and better FCR were seen in the group of lambs that fed with 4.5 gr yeast per lambs (HY group), that could probably be due to improved cellulolytic bacteria in the rumen of lambs fed probiotics supplemented diets and reduce the risk of acidosis compared to other groups specially control group, but differences between groups have not been statistically significant (P>0.05). Blood parameters which related to immune system, were unaffected by treatments. This could be due to good hygienic provided to the lambs. The differences in the type and amount of food consumed, type of probiotic or how to use it can be the reason of difference between results of this study and results of other researchers.
This study was supported by Pars Jivar Soufi Company. Also we are grateful to Mrs Leila Rostami for providing us equipment.
Abo El-Nor S.A.H. and Kholif M.A. (1998). Effect of supplementation of live yeast culture in the diet on the productive performance of lactating buffaloes. Milchwissenschaft. 53, 663-666.
Amabile-Cuevas C., Cardenas-Garcia M. and Ludgar M. (1995). Antibiotic resistance. J. Anim. Sci. 83, 320-332.
Antunovic Z., Speranda M., Amidzic D., Seric V., Steiner Z., Doma-Cinovic N. and Boli F. (2006). Probiotic application in lambsnutrition. Krmiva. 4, 175-180.
Beeson W.M. and Perry T.W. (1952). Balancing the nutritional deficiencies of roughages for beef steers. J. Anim. Sci. 11, 501-509.
Brake J. (1991). Lack of effect of all live yeast culture on broiler, breeders and progeny performance. J. Poultr. Sci. 70, 1037-1039.
Bruno R.G.S., Rutigliano H.M., Cerri R.L., Robinson P.H. and Santos J.E.P. (2009). Effect of feeding Saccharomyces cerevisiae on performance of dairy cows during summer heat stress. Anim. Feed Sci. Technol. 150, 175-186.
DavisM.E., BrownD.C., Maxwell C.V., Johnson Z.B., Kegley E.B. and Dvorak R.A. (2004). Effect of phosphorylated mannans and pharmacological additions of zinc oxide on growth and immunocompetence of weaning pigs. J. Anim. Sci. 82, 581-587.
DeSmetI., Van Hoorde L., De Saeyer Van de Woeslyne M. and Verstraele W. (1994). In vitro study of bile salt hydrolase (BSH) activity of BSH isogonics Lactobacillus plantarum 80 strains and estimation of cholesterol lowering through enhanced BSH activity. Microbial Ecol. Health Dis. 7, 315-329.
Deaville E.R. and Galbraith H. (1992). Effect of dietary protein level and yeast culture on growth, blood prolactin and mohair fibre characteristics of British Angora goats. Anim. Feed Sci. Technol. 38, 123-133.
Demir G., Klein H.O., Mandel-Molinas N. and Tuzuner N. (2007). Beta glucan induces proliferation and activation of monocytes in peripheral blood of patients with advanced breast cancer. Int. J. Immunol. Pharmacol. 7, 113-116.
Desnoyers M., Giger-Reverdin S., Bertin G., Duvaux-Ponter C. and Sauvant D. (2009). Meta-analysis of the influence of Saccharomyces cerevisiae supplementation on ruminal parameters and milk production of ruminants. J. Dairy Sci. 92, 1620-1632.
Ding J., Zhou Z.M., Ren L.P. and Meng Q.X. (2008). Effect of monensin and live yeast supplementation on growth performance, Nutrient digestibility, carcass characteristics and ruminal fermentation parameters in lambs fed steam-flaked corn-based diets. Asian-Australas J. Anim. Sci. 21, 547-554.
Dobicki A., Preś J., Łuczak W. and Szyrner A. (2005). Influence of dried brewery’s yeast on body weight gains, physiological and biochemical indicators of blood and development of the rumen micro-organisms in calves. Med. Wet. 61, 946-949.
Dobicki A., Preś J., Zachwieja A., Mordak R. and Jakus W. (2007). Influence of yeast preparations on chosen biochemical blood parameters and the composition of cow milk. Med. Wet. 63, 955-959.
Erdman J.W. (1989). Phytic acid interactions with divalent cations in foods and in gastro intestinal tract. Pp. 161-170 in Mineral Absorption in Monogastric Gastro-Intestinal Tract. F.R. Dintizisand and J.A. Laszlo, Eds. Plenum Press, New York.
FAO. (2002). Probiotics in Food: Health and Nutritional Properties and Guidelines for Evaluation. Food and Agriculture Organization of the United Nations World Health Organization. Rome, Italy.
Fuller R. (1989). Probiotics in man and animals. J. Appl. Bacterial. 66, 365-374.
Fuller R. (1977). The Importance of lactobacilli in maintaining normal microbial balance in the crop. Br. Poult. Sci. 18, 84-94.
Fuller R. (1992). History and development of probiotics. Chapman and Hall, London, UK.
Galina M.A., Delgado M. and Ortíz M. (2006). Effect of a lactic probiotic on kids growth. Pp. 54 57th Ann. Meet. European Assoc. Anim. Prod. Wageningen, Netherlands.
Glade M.J. and Biesik L.M. (1986). Enhanced nitrogen retention in yearling horses supplemented with yeast culture. J. Anim. Sci. 62, 1635-1642.
Glade M.J. and Sist M.O. (1988). Dietary yeast culture supplementation enhances urea recycling in equine large intestine. Nutr. Reprod. Int. 37, 11-17.
Guedes C.M., Goncalves D., Rodrigues M.A.M. and Diasda-Silva A. (2008). Effects of a Saccharomyces cerevisiae yeast on ruminal fermentation and fibre degradation of maize silages in cows. Anim. Feed Sci. Technol. 145, 27-40.
Heinrichs A.J., Jones M. and Heinrichs B.S. (2003). Effects of mannan oligosaccharide or antibiotic in neonatal diets on health and growth of dairy calves. J. Dairy Sci. 86, 4064-4069.
Hernandez R., Gonzalez S.S., Pinos-Rodriguez J.M., OrtegaM.E., Hernandez A., Bueno G. and Cobos M. (2009). Effect of a yeast culture on nitrogen balance and digestion in lambs fed early and mature Orchard grass. J. Appl. Anim. Res. 35, 53-56.
Jouany J.P., Mathieu F., Senaud J., Bohatier J., Bertin G. and Mercier M. (1998). The effects of Saccharomyces cerevisiae and Aspergilus oryzae on the digestion of the cell wall fraction of a mixed diet in defaunated and refaunated sheep rumen. Reprod. Nutr. Dev. 38, 401-416.
Keyser S.A., McMeniman J.P., Smith D.R., MacDonald J.C. and Galyean M.L. (2007). Effects of Saccharomyces cerevisiae subspecies boulardii CNCM I-1079 on feed intake by healthy beef cattle treated with flor fenicol and on health and performance of newly received beef heifers. J. Anim. Sci. 85, 1264-1273.
Khalid M.F., Sarwar M., Mahr Un N. and Zia-Ur R. (2011). Response of growing lambs fed on different vegetable protein sources with or without probiotics. Int. J. Agric. Biol. 13, 332-338.
Line J.E., Bailey J.S., Cox N.A. and SternN.J. (1997). Yeast treatment to reduce Salmonella and Campylobacter population associated with broiler chickens subjected to transport stress. Poult. Sci. 76, 1227-1231.
MackieR.I., Mcsweeney C.S. and Klievea V. (2002). Microbiologyofthe rúmen. Pp. 95-118 in Sheep Nutrition. M. Freer and H. Dove, Eds. CSIRO Publishing, Canberra, Australia.
Małaczewska J. and Milewski S. (2010). Immunomodulating effect of Inter Yeast S on the non-specific and specific cellular and humoral immunity in lambs. Pol. J. Vet. Sci. 13, 163-170.
Mandour M.A., Al-ShamiS.A. and Altabari G. (2009). The effect of feeding probiotics on the productive performance of Saudi Arabia sheep breeds during. Mansoura Vet. Med. J. 11(1), 87-103.
Martin S.A., Nisbet B.J. and Dean R.G. (1989). Influence of a commercial yeast supplement on the in vitro ruminal fermentation. Nutr. Reprod. Int. 40, 395-403.
Masek T., Mikulec Z., Valpotić H., Kušće L., Mikulec N. and Antunac N. (2008). The influence of live yeast cells (Saccharomyces cerevisiae) on the performance of grazing dairy sheep in late lactation. Veterinarski Arhi. 78, 95-104.
Masek T., Mikulec H., Valpotic Snježan P., Stipetic B. and Perkic D. (2007). Influence of yeast culture (Saccharomyces cerevisiae) on performance of fattening lambs fed ground or whole grain diet. Krmiva. 4, 179-187.
Mikulec Ž., Mašek T., Habrun B. and Valpotić H. (2010). Influence of live yeast cells (Saccharomyce scerevisiae) supplementation to the diet of fattening lambs on growth performance and rumen bacterial number. Vet. Arhiv.80(6), 695-703.
Miles R.D., Arafa I.S., Harms R.H., Carson C.W., Reid B.L. and Crawford J.S. (1981). Effects of a living non freeze dried lactobacillus acidophilus culture on performance, egg quality and gut microflora in commercial layers. Poult. Sci. 60, 993-1004.
Milewski S., Wójcik R., Małaczewska J., Trapkowska S. and Siwicki A.K. (2007). Effect of β-1.3/1.6-D-glucan on meat performance and non-specific humoral defense mechanisms in lambs. Med. Wet. 63, 360-363.
Milewski S., Brzostowski H., Tański Z., Zaleska B., Ząbek K. and Kosińska K. (2009). Effect of yeast preparations Saccharomyces cerevisiae on meat performance traits and hematological indices in sucking lambs. Pp. 101 in Proc. Ann. Meet. European Assoc. Anim. Prod. Wageningen, Netherlands.
Mohamadi P. and Dabiri N. (2012). Effects of probiotic and prebiotic on average daily gain, fecal shedding of Escherichia coli and immune system status in newborn female calves. Asian-Australas J. Anim. Sci.25(9), 1255-1261.
Moore B.E., Newman K.E., Spring P. and Chandler F.E. (1994). The effect of yeast culture (Yea Sace 1026) in microbial population’s digestion in the cecum and colon of the equine. J. Anim. Sci. 72, 1-10.
Muchmore A.V., Sathyamoorthy N., Decker J. and Sherblom A.P. (1990). Evidence that specific high mannose oligosaccharides can directly inhibit antigen-driven T-cell responses. J. Leukoc. Biol. 48, 457-464.
Mukhtar N., Sarwar M., Nisa M.U. and Sheikh M.A. (2010). Growth response of growing lambs fed on concentrate with or without ionophores and probiotics. Int. J. Agric. Biol. 12, 734-738.
Newbold C.J., Wallace R.J. and Chen X.B. (1995). Differents trains of Saccharomyces cerevisiae differ in their effects on ruminal bacterial numbers in vitro and in sheep. J. Anim. Sci. 73, 1811-1818.
NRC. (1985). Nutrient Requirements of Poultry, 6th Rev. Ed. National Academy Press, Washington, DC., USA.
Onifade A.A. and Babatune G.M. (1996). Supplemental value of dried yeast in a high fiber diet for broiler chicks. Anim. Feed Sci. Technol. 62, 91-96.
Onifade A.A., Obiyan R.I., Onipede E., Adejumo O.A., Abu O.A. and Babatune G.M. (1999). Assessment of the effects of supplementing rabbit diets with a culture of Saccharomyces cerevisiae using growth performance, blood composition and clinical enzyme activities. Anim. Feed Sci. Technol. 77, 25-32.
Onifade A.A. (1997). Growth performance, carcass characteristics, organ measurements and hematology of broiler chickens fed a high fiber diet supplemented with antibiotics or dietary yeast. Die Nahrung. 41, 370-374.
Pagan J.D. (1990). Effect of yeast culture supplementation on nutrient digestibility in mature horses. J. Anim. Sci. 68, 371-380.
Rezaeian M. (2004). Effect of yeast culture supplementation on the performance of finishing Shal lambs. Proc. Br. Soc. Anim. Sci.128, 211-121.
Sales J. (2011). Effectsof Saccharomyces cerevisiae supplementation on ruminal parameters, nutrient digestibility and growth in sheep: a meta-analysis. Small Rumin. Res. 100, 19-29.
Salminen S., Isolauri E. and Salminen E. (1996). Clinical uses of probiotics for stabilizing the gut mucosal barrier: successful strains and future challenges. Antonievan Leeuwenhoek. 70, 347-358.
SAS Institute. (1997). SAS®/STAT Software, Release 6.11. SAS Institute, Inc., Cary, NC. USA.
Sharon N. (2008). Lectins: past, present and future. Biochem. Soc. Trans. 36, 1457-1460.
Shim S.B. (2005). Effects of prebiotics, probiotics and synbiotics in the diet of young pigs. Ph D. Thesis. WageningenUniversity and ResearchCenter, Wageningen, Netherlands.
Siwicki A.K., Kazuń K., Głąbski E., Terech-Majewska E., Baranowski P. and Trapkowska S. (2004). The effect of beta- 1.3/1.6-glucan in diets on the effectiveness of anti-Yersinia ruckeri vaccine-an experimental study in rainbow trout (Oncorhynchus mykiss). Pol. J. Food Nutr. Sci. 54, 59-61.
Spring P., Wenk C., Dawson K.A. and Newman K.E. (2000). The effects of dietary manna oligosaccharides on cecal parameters and the concentration of enteric bacteria in the ceca of Salmonella challenged broiler chicks. Poult. Sci. 79, 205-211.
Sykes A.R. (1978). An assessment of the value of plasma urea nitrogen and albumin concentrations as monitors of the protein status of sheep. Pp. 143-154 in The Use of Blood Metabolites in Animal Production. O.C.C. Publications, British, UK.
Thrune M., Bach A., Ruiz-Moreno M., Stern M.D. and Linn J.G. (2009). Effects of Saccharomyces cerevisiae on ruminal pH and microbial fermentation in dairy cows: yeast supplementation on rumen fermentation. Livest. Sci. 124, 261-265.
Williams P.W. (1989). Understanding the biochemical mode of action of yeast culture. Pp. 79-99 in Biotechnology in the Feed industry. T.P. Lyons, Ed. Alltech Technical Publications, Nicholasville, Kentucky.
Williams P.E., Tait C.A., Innes G.M. and Newbold C.J. (1991). Effects of the inclusion of yeast culture in the diet of dairy cows on milk yield and forage degradation and fermentation patterns in the rumen of steers. J. Anim. Sci. 69, 3016-3026.
Xiao Z., Trincado C.A. and Murtaugh M.P. (2004). Beta-glucan enhancement of T-cell IFN gamma response in swine. Vet. Immunol. Immunopathol. 102, 315-320.