Saccharomyces cerevisiae CELL WALL SUPPLEMENTATION ON GROWTH PERFORMANCE AND IMMUNITY STATUS OF WHITE SHRIMP (Litopeneaus vannamei)  

Orapint Jintasataporn1, Bonato, M. A.2, Santos, G. D.2 and Blezinger, S. B.3*
 
1Kasetsart University, 50 Ngam Wong Wan Rd, Ladyaow Chatuchak Bangkok 10900, Thailand.
2ICC Brazil - Av. Brigadeiro Faria Lima, 1768 4C, CEP:01451-909, São Paulo/SP - Brazil.
E-mail: glycon@iccbrazil.com.br
3Reveille Livestock Concepts, 667 CR 4711 Sulphur Springs, TX 75482.

The yeast cell wall contains β-glucans and mannanoligosaccharides which are functional fiber molecules shown to stimulate the immune system (innate immunity) and prevent gut pathogen colonization, respectively, in numerous species including shrimp. Enhancing the innate immune system in shrimp is important, since it does not have a specific immune system to its defense, thus prebiotics with high levels of beta-glucans become essential. The objective of this study was to evaluate effects of prebiotic (Saccharomyces cerevisiae cell wall components) dietary supplementation on growth performance, survival rate, and on immune status and disease resistance against Vibrio harveyi and Vibrio parahemolyticus causative agent of Early Mortality Syndrome disease, (EMS) of shrimp Litopeneaus vannamei.

In this trial the shrimp were distributed in a completely randomized design, with 4 diet treatments of 0, (CON) 0.25, 0.5 and 1.0% yeast concentrate product (YCW - Saccharomyces cerevisiae cell wall - ImmunoWall®, ICC, Sao Paulo, Brazil), with 8 replicates. These included 4 replicates for growth performance and 4 replicates for immunity (bacteria challenge). Each replicate consisted of 1,000 liter fiber tank with a stocking density of 60 shrimp/m3 in brackish water of 12-15 ppt. Individual shrimp of 6.45±0.26g were acclimated for one week and allocated to treatment tanks. They were fed a pelleted diet (38% of CP, and 7.5% of lipid) at 2.5-3% of body weight, 4 times daily at 07:00 a.m., 11:00 a.m., 15:00 p.m. and 19:00 p.m. The measurements of growth included total feed intake (TFI, g/tank), feed intake (FI, g/ind), daily feed intake (DFI, g/ind/d), production (g/tank) body weight (BW, g/ind), body weight gain (BWG, g/ind), average daily gain (ADG, g/ind/d), specific growth rate (SGR, %/d), feed conversion ratio (FCR), survival rate (SR, %), and  at 14 and 28 days. The immunological measurements included total hemocyte count (THC, X 105cell/ml), hemolymph protein (HP, ml/dl), and phenol oxidase activity (POx, unit/mg protein) measured at 14 and 28 d. For bacteria challenge, shrimp were fed experimental diet for 1 month after which 30 shrimps from each treatment were randomly extracted to challenge with pathogenic bacteria by intramuscular injection. Infection dose was 2.6x106 CFU/mL of Vibrio parahemolyticus and 1.0x106 CFU/mL of Vibrio harveyi. Three hours post injection, hemolymp was collected to determine immune response and evaluate bacteria clearance ability, which was efficiency of YCW to enhance the shrimp immune defense system. The THC, HP and POx were evaluated weekly. Mortality rate (MR, %) was determined daily, for 7 days. The data were analyzed using the GLM (SAS), and means were compared by Ducan's test (P=0.05).

YCW supplementation at 0.5 and 1.0% improved (P<0.05) BW at d 14, and TFI, FI and DFI at d 28. HP improved at d 7 and 14 and POx improved at d 21 (P<0.05) at all YCW feeding levels compared with control group. After V. harveyi challenge the MR were lower (P<0.05) in groups fed YCW, at days 2 and 3 after challenge. Also THC and HP were higher (P<0.05) in groups fed with 0.5 and 1.0% of YCW. For V. parahemolyticus challenge, THC improved for all YCW levels. YCW fed at 0.5 and 1.0% tended to promote better immunological support illustrated by lower mortality rates (55.6 and 77.8% respectively compared to CON) after V. parahemolyticus challenge. This response was further reflected in shrimp performance that was improved 15 and 6.5% by YCW feeding levels of 0.5 and 1.0% respectively for BWG and FCR at 28 days. The yeast cell wall supplementation at 0.5 and 1% in shrimp diets resulted in improved body weight gain and feed intake. The 1% YCW inclusion rate was shown to enhance some immunity parameters under disease challenge condition by Vibrio harveyi and Vibrio parahemolyticus.