Products from little researched plants as aquaculture feed ingredients

Read Also

As the World’s human population continues to expand beyond 6 billion, its reliance on farmed fish production as an important source of protein will also increase (Naylor et al., 2000). Projections of world fishery production in 2010 range between 107 and 144 million tonnes (FAO, 2000). Most of the increase in fish production is expected to come from aquaculture, which is currently the fastest growing food production sector of the world. By the year 2030, aquaculture will dominate fish supplies and more than half of the fish consumed is likely to originate from this sector (FAO, 2000). The projected total production of feeds for aquaculture in the year 2010 range from 25 million metric tonnes (mmt; Tacon and Forster, 2001) to 32.6 mmt (IFOMA, 2000) against an approximate production estimate of about 13 mmt in the year 2000. Requirements for aquaculture feeds are likely to be further increased by an increasing trend towards the intensification of farmed production of omnivorous species in Asian countries, particularly China.

The proportion of global fishmeal production used in fish feeds has increased from 10 to 35 per cent in the last fifteen years (Hardy, 2000). Predictions of fishmeal needs for aquaculture feeds in 2010 are 2.8 mmt, approximately 44 per cent of the ten-year average global fishmeal production of 6.5 mmt. This is in spite of the predicted decrease from current levels of the percentage of fishmeal included in the feed of all, major aquaculture species. Hardy (2000) estimates that this amount of fishmeal would be approximately 1.3 mmt less than that required had there been no decline in fishmeal use in fish feeds. At least this amount of fishmeal equivalent alternative protein sources (to the order of approximately 3 mmt) would be required in the aquaculture industry yearly by the year 2010.

The need to identify appropriate, new sources of protein is therefore imperative. It is highly desirable that the selected protein sources do not conflict with human food security interests. It is worth mentioning in this context that fish that could form human food are converted into fishmeal for use in animal feeds in countries such as Peru for economic reasons. The importance of the development of non-human-food grade feed resources whose growth can cope with the projected and desired fast growth of the sector has been stressed (Tacon and Forster, 2001). Recent outbreaks of diseases such as BSE in livestock, arguably caused by feeding animal products to animals that do not normally consume them, have cast doubts regarding the suitability of feeding animal-derived proteins to non-carnivorous species. Plants therefore become the preferred sources of protein for these species. There have been a number of efforts in the past decades to test the suitability of a number of plant-derived protein sources for various, popular aquaculture species. Many of these have concentrated on species such as soybean, rapeseed (canola) meal, sunflower seed meal, cottonseed meal, peanut meal, wheat and corn gluten. Most of these plants require environmental and soil conditions and energy subsidies that restrict the scope for increasing their production. With the prospects of increasing direct human demand for nutrients derived from these sources they could not be expected to contribute greatly towards satisfying demands from new sources such as the aquaculture feed industry.

There is, therefore, a need to examine other plants that can grow on degraded soil and require lower external energy subsidies. Alongside their potential in the production of feed ingredients, these species can help reclamation of degraded areas. Furthermore, their development may be aided by the national, international and private funding that is being channelled into wasteland reclamation. According to World Resources Institute (WRI) estimates, there were about 1.2 billion hectares of eroded land (11 per cent of the Earth’s vegetated surface) in 1990. Since 1990, an additional 5 to 6 million ha per annum are lost to severe soil degradation, again according to WRI estimates. Conventional, agricultural production would eventually become nonviable in a large proportion of these lands. The International Food Policy Research Institute (IFPRI) data indicate that soil degradation has already significantly lowered the productivity of 16 per cent of farm-land, world-wide. Several, hardy plant species can assist in reclamation of eroded land by increasing the organic matter content of the soil and acting as carbon sinks and dust traps. Alley-cropping with these plants would enable inter-cropping with annuals such as vegetables a few years after initial planting. These multipurpose plants and their products, taking their availability and potential for growth into account, could be considered as protein sources in feeds after adequate treatment. Reclamation of eroded and unproductive land would be an additional benefit. Asia, which accounts for more than 90 per cent of global, aquaculture production, is estimated to have 11 per cent wasteland, 15 per cent lightly or moderately degraded and 3 per cent strongly or extremely degraded land according to UN figures. China and India, that together account for about 75 per cent of the total aquaculture production, are indicated as being severely affected by land degradation. There exist therefore possibilities for regional and local integration of feed ingredient production from wasteland and their use in aquaculture production.

Plants that are capable of resisting adverse soil and climatic conditions often contain high levels of anti-nutritional, toxic principles that keep herbivores at bay. Utilisation of these plants as animal or fish feeds would therefore depend, not only on their nutritional content, but also the presence and level of various toxic principles and methods of detoxification. The purpose of this paper, therefore, is to highlight lesser-utilised and researched plant species capable of growing on degraded lands under stressful environmental conditions and still sustaining a reasonable production of nutrient rich products having potential as fish feed ingredients. The levels of and detoxification procedures for the various anti-nutrients present are also discussed.