A defatted microalgae (Haematococcus pluvialis) meal as a protein ingredient to partially replace fishmeal in diets of Pacific white shrimp (Litopenaeus vannamei, Boone, 1931)

Abstract

This trial evaluated the effects of partial replacement of fishmeal protein by a defatted microalgae meal (DMM) in a shrimp diet. The DMM was a by-product of astaxanthin production from Haematococcus pluvialis and contained 40.3% crude protein (CP) and 0.9% crude lipid (CL). Test diets were prepared by using DMM (3, 6, 9 and 12% in a diet) to replace 12.5%, 25%, 37.5% or 50% of a fishmeal protein in a control diet (32.3% CP & 8.9% CL). All test diets had similar protein and lipid levels. Each diet was randomly assigned to four tanks (12 juvenile shrimp per tank) in an indoor flow through seawater laboratory. After an 8-week feeding trial, shrimp fed the diet with 12.5% of the fishmeal protein replaced showed a significantly higher growth rate and lower feed conversion ratio than the shrimp fed the control diet (P < 0.05). The other three DMM-added diets had a similar effect on the growth of shrimp as the control diet (P > 0.05). Shrimp fed the four DMM-added diets appeared redder and contained higher free and esterified astaxanthins than shrimp fed the control diet. The results indicated that DMM could be a valuable alternative protein and pigmentation ingredient in shrimp feed.

Introduction

Many species of microalgae have been used to produce nutraceutical or biofuel products (Acien-Fernandez et al., 2003, Mata et al., 2010, Singh and Gu, 2010). For example, Haematococcus pluvialis (astaxanthin), Dunaliella salina (β-carotene) and Muriellopsis sphaerica (lutein) have been used for carotenoid production; Odeontella aurita, Phaedactylum tricomutum and Isochrysis galbana have been used for algae oil or omega-fatty acid production; and Chlorella, Nannochloropsis, Chaetoceros and Dunaliella species have been used for biodiesel production or development (Acien-Fernandez et al., 2003, Jin and Melis, 2003, Mata et al., 2010). These production activities can result in huge amounts of defatted microalgae by-products. The defatted microalgae meal (DMM) may contain many valuable nutrients for animal feed, such as proteins, carbohydrates, minerals, water-soluble vitamins, and bioactive compounds even though most of the lipid and lipid-soluble nutrients have been removed (Ju et al., 2009). Researchers (Cuzon et al., 1981, Hanel et al., 2007, Ju et al., 2009) found that microalgae proteins could be promising substitutes for fishmeal protein or as a valuable additive in aquafeeds.

Application of many species of microalgae in shrimp feed is still in the research stage and only a few have been tested in shrimp trials (Cuzon et al., 1981, Hasan and Chakrabarti, 2009, Ju et al., 2009). The feeding trials on shrimp revealed that some microalgae had enhancing growth effects. Cuzon et al. (1981) reported that lipid free fraction of Spirulina meal promoted growth of Penaeus japonicas and suggested that the microalgae might contain an unknown growth factor. Nakagawa and Gomez-Diaz (1995) found that whole Spirulina meal significantly improved growth, survival and feed utilization in giant freshwater shrimp (Macrobrachium rosenbergii). They suggested that the improved growth and feed utilization was probably due to the enhancement of protein assimilation. Ju et al. (2009) reported enhanced shrimp growth by inclusion of 9% whole microalgae meal of Thalassiosira weissflogii or of Nannochloropsis in the control diet. The same study found that it was the defatted meal fraction not the lipid fraction from both microalgae that resulted in enhanced shrimp growth. The enhanced shrimp growth effects were not attributed to the contribution of macronutrients from whole or defatted microalgae, as their dietary inclusions decreased crude protein and crude lipid contents and gross energy value (Ju et al., 2008, Ju et al., 2009). It is unclear what factors or compounds contained in the microalgae played a role in improving shrimp growth. In feeding trials with fish, however, microalgae have been found to increase fish digestibility, physiological activity, stress response, starvation tolerance, disease resistance, and carcass quality (Becker, 2004, Mustafa and Nakagawa, 1995).

Shrimp are omnivorous organisms and microalgae are their natural foods (Moss et al., 2006, Otoshi et al., 2001, Takeuchi et al., 2002). H. pluvialis meal or its DMM, has never been investigated as a protein ingredient in shrimp feed. However, H. pluvialis meal has frequently been added in diets to test for pigmentation of shrimp, salmon and trout (Chien and Shiau, 2005). Astaxanthin production from this microalga has reached industrial scale worldwide (Krichnavaruk et al., 2008). A company in Hawaii annually produces 70 tons of H. pluvialis meal. The H. pluvialis meal is usually treated with supercritical CO₂ to extract the fat-soluble astaxanthin for human nutraceutical and cosmetic applications due to its strong antioxidant properties (Guerin et al., 2003). The remaining DMM (> 80% biomass) has been treated as a waste by-product (Krichnavaruk et al., 2008). The extraction method using CO₂ does not contaminate the by-product and no toxic chemicals or toxic effects have been reported for the H. pluvialis algae in animal applications (Satoh et al., 2009). Therefore, DMM may have potential as an alternative protein ingredient to replace fishmeal in shrimp feed. Additionally, the left-over astaxanthin in DMM may have a pigmentation effect on shrimp. The objective of this study is to determine the effects of partial replacement of fishmeal with the defatted H. pluvialis meal on growth performance, nutritional composition and pigmentation of juvenile shrimp.