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Journal of the Persian Gulf (Marine Science)/Vol. 3/No. 9/September 2012/10/15-24 Effect of Different Levels of Dietary Supplementation of Saccharomyces cerevisiae on Growth Performance, Feed Utilization and Body Biochemical Composition of Nile Tilapia (Oreochromis niloticus) Fingerlings Asadi Rad, Mohammad; Zakeri, Mohammad*; Yavari, Vahid; Mousavi, Seyed Mohammad Department of Fisheries, Faculty of Marine Natural Resources, Khorramshahr University of Marine Science and Technology, Khorramshahr, IR Iran. Received: July 2012 Accepted: September 2012 © 2012 Journal of the Persian Gulf. All rights reserved. Abstract This study was conducted to evaluate the effect of different levels of dietary supplementation of Saccharomyces cerevisiae on growth performance, feed utilization and body biochemical composition of Oreochromis niloticus fingerlings. Four diets containing supplementation at levels of 0, 0.5, 1 and 2 g kg−1 were fed to fingerlings of Nile tilapia (5.01±0.21 g) in four replicate tanks twice daily to apparent satiation for 56 days. Growth performance increased significantly (P<0.05) with the increase in dietary yeast levels. The highest growth was obtained at 1.0–2.0 g yeast kg−1 diet. The lowest feed conversion ratio was obtained at 2.0 g yeast kg−1 diet. Linear relationship was found between dietary supplementation levels and protein efficiency ratio. Hepatosomatic index did not display any significant difference among the treatments. Whereas, Viscerosomatic index of O. niloticus fingerlings was significantly (P<0.05) affected by various supplementation levels. S. cerevisiae quantity significantly (P<0.05) affected whole fish body composition except for moisture and ash, which did not differ. The results of the present study indicated clearly that the supplementation of S. cerevisiae (1.0 g yeast kg−1 diet) enhanced the growth performance and feed utilization of O. niloticus fingerlings. Keywords: Saccharomyces cerevisiae, Growth performance, Feed utilization, Body composition, Oreochromis niloticus fingerlings on a wide variety of natural and artificial diets, are the most abundantly cultured species worldwide (Welker and Lim, 2011). They are presently cultured in virtually all types of production systems, in both fresh and salt water, and in tropical, subtropical and temperate climates (Fitzsimmons, 2006). Tilapia dominate both small and large scale aquaculture in many tropical and subtropical countries, both as low price commodity for mass consumption as a staple protein source and as a 1. Introduction Tilapia, because of their enormous adaptability to a wide range of physical and environmental conditions, ability to reproduce in captivity, relative resistance to handling stress and disease-causing agents compared to other cultured finfish species, good flesh quality, feed on a low trophic level and excellent growth rate * E-mail: [email protected] 15 Asadi Rad et al. / Effect of Different Levels of Dietary Supplementation of Saccharomyces… high value, upscale product for export markets (Lim and Webster, 2006). However, they are increasingly recognized as the species of choice for intensive aquaculture and are likely to become the most important cultured fish in the world (He et al., 2009). Probiotics are live microbial feed supplement which beneficially affect the host animal by improving its intestinal balance as supplements to improve growth (Fuller, 1989; Kesarcodi-Watson et al., 2008) and in some cases as a mean of replacing antimicrobial compounds (Moriarty, 1997). On the other hand, their effectiveness to mitigate the effects of stress, resulting in a greater production (Ghazalah et al., 2010). Current probiotic applications and scientific data on mechanisms of action indicate that non-viable microbial components act in a beneficial manner and this benefit is not limited just to the intestinal region (Salminen et al., 1999). Multiple ways exist in which probiotics could be beneficial and these could act either singly or in combination for a single probiotic. These include: inhibition of a pathogen via production of antagonistic compounds, competition for attachment sites, competition for nutrients, alteration of enzymatic activity of pathogens and nutritional benefits such as improving feed digestibility and feed utilization (Fuller, 1989; Fooks et al., 1999; Gatesoupe, 1999; Bomba et al., 2002). Olvera et al. (2001) concluded that yeast have a positive effect on fish performance when cultured under stress condition of lowering dietary protein, leading to improving growth and feed efficiency. Many studies concluded the positive effect of using viable microorganisms in probiotic mixtures into diets of fish (Li and Gatlin 2004; Brunt and Austin, 2005; Pangrahi et al., 2005; Barnes et al., 2006; AboState et al., 2009). There are a wide range of microalgae, yeast (Saccharomyces), gram positive (Bacillus, Lactococcus, Micrococcus, Carnobacterium, Enterococcus, Lacobacillus, Streptcoccus, Weisslla) and gram negative bacteria (Aeromonas, Alteromonas, Photorhodobacterium, Pseudomonas and Vibrio) that have been evaluated as a probiotics (Gastesoupe, 1999). Among probiotics, the case of Saccharomyces cerevisiae, so called, "baker’s yeast", is a unicellular fungus. Possible use of baker’s yeast in fish diets has many advantages. Firstly, it can be produced rapidly, easily and inexpensively and, at the same time, it is very stable. Secondly, it can be recycled from other industries and is also a natural substances with no negative effects both to the animals and to the environment (Tewary and Patra, 2011). The oral administration or injection of the S. cerevisiae has been shown to increase growth performance of tilapia and carp (Korkmaz and Cakirogullari, 2011; He et al., 2009). Lara- Flores et al. (2003) evaluated the effects of probiotics on growth performance in Nile tilapia. They found that the fry fed diets with the yeast Saccharomyces cerevisiae supplement exhibited greater growth than those fed the same diet without probiotic. The present paper discusses the effects of the dietary intake of the S. cerevisiae as supplementary feed compared to controled diets. 2. Materials and Methods 2.1. Experimental System The experiment was conducted in 16 polyethylene tanks in Aquaculture Wet Laboratory, Department of Fisheries, Faculty of Marine Natural Resources, Khorramshahr University of Marine Science and Technology, Iran. Each tank was filled with freshwater up to level of 50 Cm and maintained constant throughout the experimental period of 56 days. About 270 healthy tilapia fingerlings used in the experiment were purchased from University of Applied Science, Ahwaz, Iran. The fingerlings were acclimatized in tank for two weeks to prevailing laboratory condition of water temperature (31-33 °C) and pH (7.42–7.53). Aeration was provided continuously except during feeding to maintain dissolved oxygen above 6 mg L−1. During this period, the fingerlings were fed to satiation twice a day with controled diet. After acclimatization, 12 normal and healthy tilapia fingerlings were 16 Journal of the Persian Gulf (Marine Science)/Vol. 3/No. 9/September 2012/10/15-24 randomly selected, weighed and assigned to a different tank. Before weighing, fish were anesthetized using MS-222 (60 mg L−1) to reduce their stress. The average initial body weight and length of fingerling were 5.01±0.21 g and 2.74±0.18 Cm, respectively. The water quality (pH, DO, Alkalinity, Ammonia) of the experimental tank was monitored periodically once in a week following the methods of APHA (1992) and maintained at normal level. During this period, all fish were exposed to a natural photoperiod (light periods ranging from 12 h to 13 h) with similar light conditions for all tanks. Four replicates (quadruplicate) were followed for each treatment. 30 min after feeding by pipetting and then, dried at 75°C. After every 14 days, all fishes from each tank were weighed individually for recording weight. During the experimental period, water in each ant was refreshenrd with the same freshwater 25% of original volume, once a day (Table 1). 2.3. Proximate Analysis Initial body composition of fish was analyzed from 15 samples of fish frozen at -20 °C prior to the commencement of trial. At the end of experiment, all fish were weighed. Three fishes from each replicate were sacrificed for the analysis of proximate composition of body. In addition, three fishes from each tank were dissected and liver and viscera were weighed to determine hepatosomatic index (HSI) and viscerosomatic index (VSI), respectively. Proximate composition of experimental diets and whole body proximate composition were analyzed using standard methods (AOAC, 1997). Each analysis was conducted in triplicate. Moisture was determined by drying the samples in an oven at 105 °C for 24 h to a constant weight; Ash was determined by incineration of samples in a muffle furnace at 550 °C for 12 h; Crude protein (N6.25) was measured by Auto kjeldahl unit (Buchi, German; model B-414, K-438, K-371 and K-370); Total lipid was extracted from samples by homogenization in chloroform and methanol (2:1, v/v) (Bligh and Dyer, 1959), methylated and transesterified with boron trifluoride in methanol (AOAC, 1997). Gross energy was calculated based on 0.017, 0.0398 and 0.0237 MJ/g for carbohydrate, lipid and protein, respectively. 2.2. Feeding Trial The formulation of the basic diet was as such to give 41.10% crude protein, 12.76% lipid, 7.59% ash, 30.89% carbohydrate and 6.87% moisture. Four diets (control, Exp-1, Exp-2 and Exp-3) were prepared, each supplemented with 0, 0.5, 1 and 2 g kg−1 probiotics diet, respectively. Dry yeast was added to diet. The diets were prepared by thoroughly mixing the dry ingredients with oil, then adding cold water until stiff dough resulted. The dough was placed into a grinder for through mixing and extruded through 1.0 mm diameter strand. Diet was stored at -20 °C until used. Control feed was prepared in the same way without the addition of yeast. Proximate composition of the four prepared feeds (Conttrol, Exp-1, Exp-2, Exp-3) are detailed in (Table 1). During the experimental periods, fish were hand-fed to satiation twice a day (about 09:00 and 17:00) with corresponding supplementary levels. Uneaten food in the tank of each replicate was collected Table 1. Proximate composition of experimental probiotic diet (g 100 g dry diet − 1)a Experimental Gross Energy Moisture Crude protein Fat Ash Carbohydrateb diets (MJ g-1)c Control 7.78±0.14 41.85±0.17 12.36±0.07 7.32±0.14 30.89±0.48 2.01±0.02 Exp-1 7.21±0.09 41.31±0.24 12.70±0.10 7.34±0.07 31.44±0.52 2.02±0.01 Exp-2 6.34±0.05 40.87±0.32 12.78±0.11 8.01±0.07 32.00±0.59 2.02±0.01 Exp-3 6.16±0.12 40.37±0.31 13.18±0.15 7.67±0.11 32.52±0.64 2.03±0.02 a Value are means of three replicate samples per diet. b Carbohydrate, calculated by difference. c Gross energy, calculated based on 0.017, 0.0398 and 0.0237 MJ/g for carbohydrate, lipid and protein, respectively. 17 Asadi Rad et al. / Effect of Different Levels of Dietary Supplementation of Saccharomyces… 2.4. Data analysis correlate the results obtained. A one-way analysis of variance (ANOVA) was used to determine differences among supplementary levels, using SPSS 11.5 statistical software. Differences were considered significant at an alpha of 0.05 (P<0.05). Tukey’s HSD multiple comparison test was used to determine significant differences among means. Growth performance was determined and feed utilization was calculated as following: (1) Daily weight gain (DWG, g) = [mean final body weight (g)- mean initial body weight (g)]/number of days. (2) Body weight gain (BWG, %) = [(final body weight (g) - initial body weight (g)) /initial body weight (g)] ×100. (3) Specific growth rate (SGR, % day− 1) = [(Ln final weight- Ln initial weight) ×100]/ duration in days. (4) Condition factor (CF) = (fish mass / fish total length3) ×100. (5) Feed conversion ratio (FCR) = [dry weight of feed (g)/ wet weight gain (g)]. (6) Protein efficiency ratio (PER) = Increment in body weight (g)/ protein intake (g). (7) Daily feed intake (FI, g d− 1fish− 1)= diet consumed × 100 / duration in days /fish number per tank (8) Hepatosomatic index (HIS) = [weight of liver (g)/total weight of fish (g)] ×100. (9) Viscerosomatic index (VSI) = [weight of viscera (g)/total weight of fish (g)] ×100. Data are expressed as mean ± standard error. Simple linear and non-linear regressions were performed to 3. Results The growth performance and feed utilization of O. niloticus fingerlings fed different levels of dietary supplementation of S. cerevisiae are given in Table 2. Final fish weight, weight gain, and specific growth rate increased significantly (P<0.05) with the increase in dietary yeast levels. While, there were not significantly different from these parameters by diet Exp-3 and Exp-2. The highest growth was obtained at 1.0 –2.0 g yeast kg−1 diet, whereas the control diet produced the lowest growth. Results showed that daily weight gain did not display any significant difference among the four dietary supplementation levels. Condition factor was influenced by dietary treatment, with fish fed diet containing 1.0 g yeast kg−1 diet showed significantly higher CF as compared to the other diets. While, there was not significantly different from CF by diet Exp-2 and Exp-3. Table 2. Growth performance and feed utilization of O. niloticus fingerlings fed different levels of dietary supplementation of S. cerevisiae Treatmenta Control Exp-1 Exp-2 Exp-3 Initial Weight (g) 5.02±0.22 4.93±0.26 5.05±0.22 5.05±0.22 Final Weight (g) 12.27±0.33 c 12.82±039 b 13.33±0.45 a 13.35±0.48 a 7.89±0.26 b 8.28±0.28 a 8.30±0.24 a Weight gain (g) 7.25±0.23 c b 0.13±0.01 0.14±0.01 0.15±0.01 0.15±0.01 DWG (g) 144.3±2.26 c 160.1±1.98 b 164.0±2.14 a 164.5±1.77 a BWG b (%) b −1 b ab a 1.60±0.04 1.71±0.03 1.73±0.01 1.74±0.02 a SGR (% day ) b b b a 0.87±0.01 0.88±0.01 1.07±0.01 1.06±0.01 a CF 1.47±0.03 a 1.34±0.05 b 1.19±0.04 c 1.14±0.04 c FCR b b c bc b 1.65±0.02 1.82±0.03 2.05±0.03 2.14±0.01 a PER 10.67±0.10 a 10.55±0.09 a 9.83±0.09 b 9.43±0.11 c DFI b (g d− 1fish− 1) b HIS (%) 2.10±0.01 2.21±0.02 2.16±0.02 2.08±0.01 7.41±0.12 c 7.72±0.17 b 8.13±0.14 a 7.54±0.15 bc VSI b (%) Mean ± SE values (n=6) with different superscripts in each row are significantly different (P<0.05). a Control, Exp-1, Exp-2 and Exp-3 supplemented with 0, 0.5, 1 and 2 g S.cerevisiae kg−1 diet, respectively. b DWG (Daily weight gain), BWG (Body weight gain), SGR(Specific growth rate), CF ( Condition factor), FCR (Feed conversion ratio), PER (Protein efficiency ratio), DFI ( Daily feed intake), HIS (Hepatosomatic index), VSI (Viscerosomatic index). Parameters 18 Journal of the Persian Gulf (Marine Science)/Vol. 3/No. 9/September 2012/10/15-24 The lowest FCR was obtained at 2.0 g yeast kg−1 diet. It was not significantly different from FCR by diet Exp-3 and Exp-2. Fish fed the control diet consumed less feed giving a higher FCR. On the other hand, S. cerevisiae supplementation improved protein efficiency ratio; linear relationship was found between dietary supplementation levels and PER. However, fish fed 1.0–2.0 g yeast kg−1 diet had the highest PER. Conversely, fish fed controled diet consumed more diet than the other treatments. HSI did not display any significant difference among the treatments. Whereas, VSI of O. niloticus fingerlings were significantly (P<0.05) affected by various S. cerevisiae levels, with fish fed diet containing 1.0 g yeast kg−1 diet showed significantly higher VSI as compared to the other treatments. Proximate composition (% wet weight) of whole body of O. niloticus fingerlings fed different levels of dietary supplementation of S. cerevisiae is shown in Table 3. S. cerevisiae supplementation significantly (P<0.05) affected whole fish body composition except for moisture and ash, which did not differ (P>0.05). The body protein content significantly increased linearly (57.78±0.8 %) with enhanced feeding supplementation levels up to 1% (Table 3) but no further increase was observed when feeding supplementation levels was increased beyond 1%. Generally, yeast supplementation appeared to improve protein content. While, fish fed the control diet had the lowest body protein content. Biochemical analysis of carcass of O. niloticus fingerlings showed that increasing levels of S. cerevisiae supplementation resulted in an increase in the content of body lipid. Fish fed diets containing 1.0 g yeast kg−1 exhibited higher lipid content (P<0.05). Whereas, the fish fed control diet produced the lowest lipid content. 4. Discussion Since the first use of probiotics in aquaculture, a growing number of studies have demonstrated their ability to increase the growth rate and welfare of farmed aquatic animals (Lara-Flores et al., 2003; Carnevali et al., 2004; Macey and Coyne, 2005; Wang et al., 2005; Wang and Xu, 2006; Wang, 2007). Brewer’s yeast, S. cerevisiae has been recognized to have the potential as a substitute for live food in the production of certain fish (Nayar et al., 1998) or as a potential replacement for fish meal (Oliva-Teles and Gonçalves, 2001). Researchers have evaluated the nutritional value of brewers yeast, S. cerevisiae in Nile tilapia (Medri et al., 2005; Abdel-Tawwab et al., 2008; Korkmaz and Cakirogullari, 2011), Rohu (Tewary and Patra, 2011), lake trout (Rumsey et al., 1990), rainbow trout (Rumsey et al., 1991) and sea bass (Oliva-Teles and Goncalves, 2001) by comparing growth performance and feed utilization. According the results of this study, an improvement of the growth rate of the tilapia, O. niloticus, one of the most important farmed species for the world, was as a result of supplemented feed with S. cerevisiae. Probiotics may improve digestion by stimulating production of digestive enzymes or through other alterations in the gut environment, which could translate to improved growth performance (Welker and Lim, 2011). Table 3. Proximate composition (% wet weight) of whole body of O. niloticus fingerlings fed different levels of dietary supplementation of S. cerevisiae. Treatmenta Parameters Initial Control Exp-1 Exp-2 Moisture 74.82±0.5 73.91±0.7 72.21±0.7 72.39±0.8 Crude protein 55.47±1.2 c 56.87±1.1 b 57.45±1.2 ab 57.78±0.9 a Crude lipid 25.66±0.9 c 26.13±0.8 b 26.19±0.7 b 26.78±0.8 ab Ash 13.57±0.7 13.33±0.5 14.28±0.6 14.16±0.5 Mean ± SE values (n=3) with different superscripts in each row are significantly different (P<0.05). a Control, Exp-1, Exp-2and Exp-3 supplemented with 0, 0.5, 1 and 2 g S.cerevisiae kg−1 diet, respectively. 19 Exp-3 71.87±0.7 55.70±1.1 c 27.11±0.9 a 13.83±0.6 Asadi Rad et al. / Effect of Different Levels of Dietary Supplementation of Saccharomyces… tilapia (Abdel-Tawwab et al., 2008). Evidence is available that indicates gastrointestinal bacteria take part in the decomposition of nutrients, provide the macroorganisms with physiologically active materials (Bairagi et al., 2002, 2004; Ramirez and Dixon, 2003; Sugita et al., 1992, 1997; Waché et al., 2006; Wang, 2007; Wang and Xu, 2006; Ai et al., 2011), and thus facilitate feed utilization and digestion. This may account for the enhanced PER by dietary S. cerevisiae supplementation in the present study. Lara-Flores et al. (2003) found that the addition of live yeast improved diet and protein digestibility, which may explain the better feed efficiency seen with yeast supplements. Similar observations were made in sea bass (Tovar et al., 2002) and rainbow trout (Waché et al., 2006). No explanation on the mechanism responsible for the improved protein utilization is provided, but bacteria, including Aeromonas commonly found in the gut of tilapia, are known to produce proteases (Nayak, 2010b). Gut microbes produce amino acids that are utilized by tilapia (Newsome et al., 2011). The evidence showed that symbiotic gut microbes in tilapia contributed to nutrient production substantially, especially when nutrient requirements were not being fully met by the diet (Welker and Lim, 2011). S. cerevisiae supplementation significantly affected the whole-fish body protein and lipid contents. AbdelTawwab et al. (2008) suggested that yeast supplementation played a role in enhancing food intake with a subsequent enhancement of fish body composition. Moreover, due to the nutrient utilization and the high nutrient digestibility, the deposited nutrients increased. On the other hand, changes in protein and lipid content in fish body could be linked with changes in their synthesis, deposition rate in muscle and/or different growth rate (Smith, 1981; Fauconneau, 1984; Soivio et al., 1989; Abdel-Tawwab et al., 2006; 2008). However, Abdel-Tawwab et al. (2008) reported that fish fed the controled diet had the lowest protein content. However, yeast supplementation appeared to have improved protein The gut microbial population is also important to the nutrition of fish by increasing nutrient uptake and utilization, production of enzymes, amino acids, shortchain fatty acids and vitamins, and improved digestion (Merrifield et al., 2010; Nayak, 2010a; Welker and Lim, 2011). In the present study, linear relationship was found between dietary supplementation of S. cerevisiae level and growth performance. Abdel-Tawwab et al. (2008) reported that weight gain and specific growth rate of tilapia increased significantly (P<0.05) with the increase in dietary yeast levels. Fish fed the diet containing S. cerevisiae exhibited the greatest increase in growth performance, which was attributed to significantly higher activity of alkaline phosphatase (Gawlicka et al., 2000; German et al., 2004). LaraFlores et al. (2003; 2010) revealed that S. cerevisiae supplementation produced significantly higher weight gain and feed utilization efficiency in tilapia fed diets containing 27% or 40% crude protein compared to the controled diet. Similar pattern that improved growth performance in tilapia fed S. cerevisiae diets have been reported by Marzouk et al. (2008), Osman et al. (2010) and Ozório et al. (2012). Despite that, Shelby et al. (2006) and He et al. (2009) revealed that growth performances of tilapia were not significantly influenced by different dietary supplementation of S. cerevisiae levels. This might be because of differences in experimental conditions, water quality and duration of study, 56 days in this study. The present study showed that inverse relationship existed between dietary supplementation of S. cerevisiae level and FCR. Whereas, linear trend was observed in PER with increasing trend associated with higher inclusion of supplementation. This study clearly showed that the PER improved property of the probiont S. cerevisiae. Few studies have examined the impact of probiotics on nutrient uptake and utilization in fish, including tilapia and there are reports of improved nutrient utilization through probiotic use in tilapia and other species of fish (Welker and Lim, 2011). The supplementation of commercial live yeast improved feed utilization on 20 Journal of the Persian Gulf (Marine Science)/Vol. 3/No. 9/September 2012/10/15-24 content without significant difference. The discrepancy in the results might be mainly due to the different experimental conditions. The digestive tract of hydrobionts is an open system constantly interacting with the surrounding environment. As a result, the establishment, proliferation and function of the probiotics in the digestive tract are largely influenced by various environmental factors, such as water quality, hardness, dissolved oxygen, temperature, pH, osmotic pressure, mechanical friction and the environmental microflora (Das et al., 2008; Mehrim, 2009; Ai et al., 2011). The results of the present study indicated clearly that the supplementation of S. cerevisiae (1.0 g yeast kg−1 diet) enhanced the growth performance as measured by final weight and SGR and feed utilization of fingerling tilapia. It is difficult to draw concrete conclusions and provide specific recommendations on the effects of dietary probiotics on growth performance of tilapia given that the studies vary widely with regard to fish age and size, stocking density, diet composition, dietary probiont concentration, feed allowances, feeding duration, and of course, type and source of probiont (Welker and Lim, 2011). The stimulatory effect of dietary S. cerevisiae on immune parameters and resistance of tilapia to infectious pathogens need further investigations. Abdel-Tawwab, M., Khattab, Y.A.E., Ahmad, M.H. and Shalaby, A.M.E., 2006. Compensatory growth, feed utilization, whole body composition and hematological changes in starved juvenile Nile tilapia, Oreochromis niloticus (L.). Journal of Applied Aquaculture. 18:17–36. Abdel-Tawwab, M., Abdel-Rahman, A.M. and Ismael, N.E.M., 2008. Evaluation of commercial live bakers' yeast, Saccharomyces cerevisiae as a growth and immunity promoter for fry Nile tilapia, Oreochromis niloticus (L.) challenged in situ with Aeromonas hydrophila. Aquaculture. 280:185-189. Ai, Q., Xu, H., Mai, K., Xu, W., Wang, J. and Zhang, W., 2011. Effects of dietary supplementation of Bacillus subtilis and fructooligosaccharide on growth performance, survival, non-specific immune response and disease resistance of juvenile large yellow croaker, Larimichthys crocea. 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