FEATURE
IMMUNE RESPONSE Dietary protease improves immune responses in Pacific White Shrimp, Litopenaeus vannamei
by Hoongli Song, Guangdong Ocean University, Zhanjiang, China, Yao Liu, Nutritech Solutions Inc., Shanghai, China, Xiao-hui Dong, Guangdong Ocean University, Zhanjiang, China and M. A. Kabir Chowdhury, Jefo Nutrition Inc., Saint-Hyacinthe, Quebec, Canada
G
lobal farmed crustacean production has been increasing at much faster rate than major farmed species. It is expected to reach 6.8 million metric tons (MMT) in 2015, of which, 69 percent or 4.7 MMT will be from the marine shrimps (Figures 1A, 1B). In the last 15 years, the production increased six-fold driven more by intensification rather than expansion of the area cultivated.
protease is considered to be an important tool for better nutrient utilisation. It is hypothesised that a better nutrient profile and utilisation can compensate poor immune or stress responses. Specially, when high quality ingredients are partially or completely replaced by more economical protein sources, which are often of poor quality.
The study
The study, consisting of five treatments, was conducted at the Guangdong Ocean University of China. The objective of the study was to assess the changes in immune response to low fishmeal diets supplemented with a commercially available dietary protease. Two diets were prepared: one with 20 percent fishmeal (positive control) and the other with 10 percent fishmeal (negative control). The fishmeal was replaced by increasing peanut meal (16 percent) and soybean meal (28 percent) contents compared to 11 percent and 16 percent, respectively from
the positive control diet for equal amount of crude protein. Another three diets were prepared by adding graded level (125, 150 and 175 ppm) of a commercial protease complex (Jefo Nutrition Inc., Canada) to the mash of the negative control diet. The activities of acid (ACP) and alkaline (AKP) phosphatases, superoxide dismutase (SOD) and polyphenol oxidase (PO) were analysed in both serum and hepatopancreas of 15 shrimps per dietary treatment. The malon-di-aldehyde (MDA) content was analysed only in serum. Regression analysis was performed to assess the effects of the intake of dietary protease on these responses. No differences in enzymatic activities and MDA contents were observed between the shrimps fed the 20 percent fishmeal diets and the 10 percent fishmeal diets supplemented with 175 ppm protease. The results of the regression analysis with protease intake (µg/ shrimp) at 0, 125, 150, 175 ppm of the 10
The development of specific pathogen free (SPF) broodstock of Pacific white shrimp has been the major contributing factor to this intensification, and the accompanied spectacular growth. This has resulted in a much higher demand for compounded feed. The current demand for feed is estimated to be 6.8 MMT or 90 percent of the production. This is about four times higher than 1.75 MMT or 77 percent of the production in 2000 (Tacon and Metian, 2015). However, the overintensification and improp- Table 1. Regression of the protease intake per shrimp with various immune parameters and 96-h cumulative mortality of er management, the lack shrimps fed graded level of protease of proper knowledge on Min Max Adj R2 MSE t-value nutritional requirements at Serum Acid phosphatase - ACP (KAU/ml) 2.6 5.9 72% 0.37 6.28*** various stages and over or Alkaline phosphatase - AKP (KAU/ml) 2.6 6.6 70% 0.55 5.9*** under formulation, and the Superoxide dismutase - SOD (U/ml) 345.9 411.1 75% 73.43 6.8*** increasing use of poorly Phenol oxidase - PO (U/ml) 515.7 958.2 60% 8230.00 4.9*** digestible and poorly characterised protein sources Malon Di-Aldehyde - MDA (nmol/ml) 9.1 15.8 60% 2.40 -4.8*** while replacing fishmeal, Min Max Adj R2 MSE t-value usually cause unwanted Hepato-pancreas Acid phosphatase - ACP (KAU/ml) 55.9 132.9 46% 234.00 3.7*** stress and poor stress Alkaline phosphatase - AKP (KAU/ml) 73.7 170.6 28% 556.00 2.6* responses in the shrimps. Superoxide dismutase - SOD (U/ml) 4.1 7.3 75% 0.30 6.8*** As a result, occasional disease outbreaks have been Phenol oxidase - PO (U/ml) 657.4 1057.4 52% 8787.00 4.1*** very common creating Cumulative mortality (%) 25% 57% 61% 0.00 -4.9*** considerable economical KAU - King-Armstrong Unit, amount of enzyme that will liberate 1 ml of phenol in 15 min; SOD U - inhibits the rate losses in many countries. of increase in absorbance at 550 nm by 50%; PO U –the change in absorbance per min at 490 nm. For t-values: *** The addition of dietary significant at 0.001; **significant at 0.01, *significant at 0.05. 32 | INTERNATIONAL AQUAFEED | May-June 2015