IMMUNOLOGICAL EFFECTS OF SPRAY DRIED PLASMA IN DIETS FOR JUVENILE WHITE SHRIMP Litopenaeus vannamei DURING LABORATORY CONDITIONS
White Feces Syndrome is highly prevalent in SE Asia shrimp farms causing high mortality and reduced biomass yield. Soybean meal (SBM) is commonly used in shrimp feed to reduce reliance on fish meal but is less digestible by shrimp and may contribute to poor pond water quality. Poor pond water quality propagates the growth of Vibrio parahaemolyticus, which is the primary pathogen associated with White Feces Syndrome and causes damage to the hepatopancreas. Evaluation of ingredients to improve immunity are needed. Spray-dried porcine plasma (SDP) is a feed ingredient composed of a mixture of functional proteins including albumen, globulin, transferrin, peptides, growth factors, and other components that improve diet digestibility, growth, feed efficiency, health, and survival in mammalian, avian, and aquaculture species. Spray-dried plasma proteins in shrimp feed may improve immunity to support shrimp health. The study objectives were to determine the effect of 0.0, 1.5, 3.0, 4.5 or 6.0% SDP replacing SBM in pelleted shrimp diets fed to post-larvae 12 (PL12) white shrimp Litopenaeus vannamei on immune responses after PL rearing for 45 days under controlled water temperature (29 ± 1°C) and optimum water quality in fiberglass tanks (4 tanks per diet; 120 PL/m2; 80 shrimp/tank).
On day 45, immune parameters were measured on 20 shrimp per diet. Also 30 shrimp per tank were kept for an additional 4 days to undergo challenge with Vibrio parahaemolyticus (105 CFU/mL; 96 hr-LD50) to evaluate post challenge survival. Five shrimp per tank were collected before challenge and 4 d after challenge for hepatopancreas histology and detection of infection.
At day 45, total hemocyte count (106 cells/mL), phagocytosis (%), phenoloxidase activity (units/min/mg protein) and superoxide dismutase (% inhibition) increased as level of SDP increased (P < 0.01). On d 4 after challenge, shrimp fed diets with 3.0, 4.5 or 6.0% SDP had lower (P < 0.05) mortality compared to 0 or 1.5% SDP and hepatopancreas histology revealed less cell damage without bacterial infection for shrimp fed diets with 3 to 6% SDP. However bacterial infection was observed in hepatopancreas cell of challenged shrimp fed diets with 0 or 1.5% SDP.
In conclusion, juvenile shrimp feed containing 3 to 6% SDP supported better immunity and under challenge with Vibrio parahaemolyticus, reduced mortality, hepatopancreas cell damage and bacterial infection. Spray dried plasma is a functional protein that can support better immunity and health of shrimp and is an excellent alternative to antibiotics, especially in countries that prohibit use of antibiotics in shrimp feed or have policies to reduce reliance on antibiotics.
