Biotechnology in Aquatic Feeds

Albert G. J. Tacon and Ian P. Forster

The Oceanic Institute

Waimanalo, Hawaii 96795

atacon@oceanicinstitute.org

Abstract

Aquaculture is the fastest growing area of food production in the US and in order for this growth to be fostered, several issues need to be addressed. In terms of feeds and nutrition, these issues include development of high quality, inexpensive nutrient sources, and methods for ensuring that the feeds do not contain pathogenic agents or toxins. Advances in biotechnology have provided tools that can be adapted to these area; namely, genetically modified feedstuffs, single-cell protein sources, probiotics, toxin and pathogen detection.

Key words: Genetically modified feedstuffs, probiotics, single-cell protein, feed safety

Introduction

Aquaculture is the fastest growing area of food production, both worldwide and in the US. The growth and intensification of aquaculture has introduced several issues that need to be addressed for the continued growth of the industry. Two of the most important issues from a nutrition and feed management perspective are the utilization of marine protein, and the elimination of pathological agents in feeds for cultured animals. Fish feeds in the US generally contain low levels of little fish meal. Shrimp feeds, however, contain higher levels of protein from marine sources. Although the shrimp culture industry is still in its infancy in the US, it is expected to grow, and with it, its demand for marine protein. Because of the relatively high cost and variable supply of fish meal, efforts have been made to reduce or eliminate its use in all aquatic feeds. Research has been carried out for several years to replace fish meal with plant proteins, and has been successful in many cases, but these alterative sources have their own difficulties related to relatively low protein levels, presence of anti-nutritional compounds, unbalanced amino acids, reduced palatability, and in some cases, low digestibility. Biotechnological advances in the past few decades have provided methods and products that can be used to assist in the successful replacement of fish meal by alternative abundant protein sources, which can be produced in massive quantities in the United States. Already, some advances have been made in the generation of feed-grade genetically modified feedstuffs, and production of single-cell proteins sources.

Traditional methodologies employed to reduce or eliminate pathological agents in feeds (high-temperature processing, chemicals), can have deleterious effects on nutritional quality. Biotechnological approaches that show promise in this area include assisting the immune system of the culture animals by inclusion of probiotics in the feed and sterilizing the feed. In addition, recently developed techniques for the rapid and inexpensive detection of toxic compounds and pathogens have been developed that incorporate micro-chip technology, enabling routine scanning of feeds as they are prepared thereby providing an additional level of security to aquaculture operations.

Genetically Modified Feedstuffs

Feed ingredients derived from genetically modified crops have been used in limited quantities in animal (including aquatic animal) feeds in North America for two decades and there is possibility for their increased use as new products are developed. For aquatic feeds, the two most advantageous developments would be to reduce or eliminate the toxic compounds present (i.e., antinutrients such as allergens, gossypol, phytic acid, anti-enzymes) and to increase the level of specific nutrients in these ingredients (e.g., limiting amino acids such as lysine and methionine, and the introduction of n-3 fatty acid genes etc.).

Single-cell Protein (SCP)

Development of agricultural and fisheries waste-utilization technology is of increasing importance as the demand for food increases amid a limited ability for expansion of single-use feed resources. SCP products have been generated on a demonstration scale at the Unisyn Biowaste, Waimanalo, HI, and have shown promise for a number of species (channel catfish, Chinese catfish and tilapia). Other successful operations in Hawaii include, Aquasearch and Cyanotech. One of the features of SCP is that they can be produced from the byproducts from human and animal activities (uneaten food, non-food grade organic materials), which are currently discarded or pose an environmental hazard. Hawaii has a competitive advantage within the US because of its high incidence of light, and constant warm climate. SCP can also be produced through fermentation technology so as to produce specific products or nutrients, including carotenoids, amino acids, immunostimulants, and growth promotants.

Probiotics

One method of controlling the negative impact of disease organisms is to reduce their occurrence through the promotion of benign organisms that competitively exclude these pathogens or that strengthen the immune response of the cultured animal. One preferred method for introduction of these organisms or substances that promote them is through addition to the feed.

Feed Safety

The issue of pathogens and toxins in animal feeds can be addressed in part by advances in biotechnology, primarily in the areas of detection and quality control, as well as development of advanced feed sterilization techniques. One new approach is the use of sensors built onto microchips to detect micro traces of specific pathogenic substances and contaminating microorganisms.

Recommendations

Short-term:

1. Chemically assess the nutritional quality of the currently available genetically modified feedstuffs and single-celled protein sources and identify specific desired trait (e.g., reduced toxic compounds, high protein content, improved amino acid/fatty acid balance).
2. Assess the efficacy of available probiotics to improve the health and growth of aquatic animals and available devices to known pathogens and toxic compounds