September 3, 2013
Seafood quality and the hunt for fishmeal replacements
Aquaculture without fishmeal produces inferior, less healthy seafood. Fortunately, an array of alternative ingredients including yeast, algae and organic trace minerals promise to partly bridge the performance gap.
by Eric J. BROOKS
An eFeedLink Hot Topic
Despite being the world's fastest growing, most hopeful protein line, the ghost of wild catch inputs casts an increasingly heavy shadow over aquaculture. In the eighteen years since world fishmeal exports peaked in the mid 1990s, they have fallen by 45% while aquaculture output has jumped by 158% over this time.
From the late 20th century to the mid 2000s, the market was kept in balance, partly by a drastic reduction in the amount of fishmeal included in livestock diets and gradually falling inclusion rates in the rations of farmed fish themselves. The past decade however, has seen fishmeal's price skyrocket from under $400/tonne in the early 2000s to the setting of three price records in seven years, the most recent one at over US$2,000/tonne earlier this year.
Although the volume of fishmeal that can be transferred from declining livestock usage to the aqua feed sector already maxed out, aqua feed output is set to more than double, from 43 million tonnes in 2013 to a UN FAO estimated 90 million tonnes in 2030. For the last decade, fishmeal inclusion has entered a long-term secular fall in its aqua feed proportion, with soymeal, rapeseed meal and in some parts of Asia, trash fish or meat and bone meal taking its place.
Deformed fish, higher cost, fillet quality
In such a situation, the question becomes not one of whether fishmeal inclusion will fall but what are its implications for the quantity and quality of aquaculture production, and for human health. Ionnis Nengas, aquaculture nutrition expert at Alltech Europe (Greece) predicts that, "Marine feed ingredients are essential ingredients to sustain quality and sustain health of the product but not going to be commodities in the future. They will be used in hatching and juvenile stage, maybe part of the grow out diets."
Despite such impending restrictions on fishmeal use and numerous attempts to devise alternatives Nengas asks questions that belie his pessimistic skepticism on this issue, "Is there enough fishmeal and fish oil to sustain production? The answer for tin coming years is clearly no."
The reason Nengas answers in the negative is not because fish will not eat non-marine inputs, but because of their impact on their fish health, flesh quality and ultimately, human nutrition. Although, "we have to replace these ingredients with alternatives, the process that has been attempted over the last few decades with conflicting results."
He adds that, "feed extruders love plant based inputs, but do the fish?" Although such feed ingredients are plentiful relative to fishmeal, they present, "High fibre and high antinutritional ingredient challenges, along with fatty acid deficiencies and indigestible plant based feed components."
Not do plant-based aqua feeds contain significantly less protein, but a smaller proportion of it is easily digestible, and even then, the amino acid ratios are not optimal for the health of most cultivated species. They are also completely deficient in EPA and DHA, omega 3 fatty acids that are essential to the proper development of many fish types.
Insufficient fatty acids: Bad fish health, unhealthy seafood for humans
According to Nengas, alongside smaller animal size, removing fishmeal from the diet of many popular aquatic species results in, "gut structural impairment, skeletal deformation and lower fish flesh quality." Fish raised on diets where fishmeal inclusion was reduced suffered from considerably more enteritis [intestinal inflammation] and had weaker immune systems.
The latter leaves them not only vulnerable to diseases but may also prevent fish vaccines from working properly, especially if plant based feed ingredients are contaminated with mycotoxins. –And one needs to keep in mind that for the last thirty years, the successful lowering of costs for producing species ranging from salmon to shrimp was achieved by reducing the proportion of diseased, deformed or dead fish by more than the increase in feed costs over this time. Consequently, a fishmeal deficient diet's higher rates of disease, mortality and physically defective fish, if not handled intelligently, could, in principle, boost the unit costs of some farmed fish species by an amount comparable to how much was saved by reducing their fishmeal intake in the first place.
What makes the issue of adapting fishmeal alternatives is the way similar species may react differently. For example, fishmeal content was minimised in diets of Atlantic salmon, trout, sea bass and sea bream. Substituted plant-based ingredients such as soymeal and rapeseed meal where fortified with a mixture of Antarctic krill, additional fish oil (to supply omega 3 fats), methionine and threonine (to provide optimal amino acid ratios).
Although the strategic supplementation of omega 3 oils and marine feed inputs mitigated some of the worse effects of plant-based aqua feed on carnivorous fish growth, the flesh quality carries implications for human health, as heart disease, cancer, arthritis, diabetes, irritable behavior and low IQ in children have all been linked to inadequate omega 3 fat intake -which is missing in the flesh of feed-raised livestock.
According to studies explained by Nengas at the recent Aquaculture Roundtable conference in Singapore, when aqua feed's fishmeal content is reduced from 49% to 5%, at maturity Atlantic salmon are 10% smaller than their fishmeal fed counterparts but this is not the case with trout. Moreover, the trout's feed conversion ratio actually improved marginally with the substitution of plant-based feed ingredients.
--But even so, these trout lost the benefits to human health which fish are touted for: The proportion of omega 3 oils EPA and DHA in the trout's body fat fell from 15% to 6%. The ratio of omega 3 to omega fats fell from the healthy 7.0 range to just 0.7.
A similar outcome unfolded when fishmeal was faced out of the diet of farmed sea bream, with the proportion of EPA and DHA in their body fat falling from 9.9% to 3.1% and 11.8% to 5.8% respectively. Sea bream's ratio of omega 3 to omega 6 fats also fell from 7.0 to 2.0.
No healthier than meat, marketing problems ahead?
Long thought of as a fish containing 'healthy fat', Atlantic Salmon's omega 3 fatty acid ratio fared even worse, with EPA dropping from 9.1% of total body fat to 2.4%, DHA from 15.8 to 5.8%. Its omega 3/omega 6 ratio plunged from 3.9 to a mere 0.3 –an omega 3/omega 6 fat ratio hardly better than what is found in relatively 'unhealthy' fatty red meat of grain fed beef, and noticeably inferior to the omega 3 to omega 6 ratio found in grass fed beef.
Nengas concluded that on one hand, "Marine feed ingredients [fishmeal] are essential ingredients to sustain quality and sustain health of aquaculture products." On the other hand, by being forced to substitute plant-based feed ingredients in place of fishmeal, "We are destroying the reason seafood demand has increased and destroying the reason why eating seafood is healthy."
Already, because less fishmeal is being fed to farmed fish, Nengas reports that, "In some European countries, even supermarkets had to lower their DHA fat standards [for certain sea food species] down to 6%." With fishmeal inclusion levels on route to plunging to the levels reported in the above scientific experiments, unless a fishmeal substitute is found, the day may come when doctors will be unable to legally state that eating carnivorous, cold water fish like salmon is 'healthy' for you.
Alongside the fact that without fishmeal, eating sea food is no longer as 'healthy' an eating option as it once was, the impact on animal performance also creates other equally serious marketing problems. Some of these are obvious enough to be visible to consumers: These include 'gaping', or open gaps in the fish fillet muscle, and an inferior taste. Even rectifiable problems like inferior fillet colour are attracting the ire of developing country consumers, some of whom have started shunning fish due to the dyes they are known to be fed.
Yeast, algae: Part of larger solution
Although a feed substitute to fishmeal is badly needed, fishmeal itself is biochemically complex, supplying key fatty acids, amino acid ratios and enzymes, among other components. This implies that more than one feed ingredient will need to be substituted in its place. In this respect, companies like Alltech have made some progress made in finding replacements for fishmeal's digestibility and fatty acid content.
For the replacing of fishmeal's omega 3 fats, at the inclusion rates undertaken in studies, algae supplied 308% of the DHA and 3.8% of the EPA found in fishmeal made from Peruvian anchovy. At a 6% inclusion rate (versus 49% for a conventional fishmeal diet or 5% in the previous tests), carnivorous cold water fish like salmon developed as normally as they would with traditional fishmeal diets.
At rates ranging up to 15%, omega 3 fatty acid levels in the fish flesh were increased to levels comparable to the early days of fish farming when considerably more fishmeal was employed –and enough to be considered an important source of omega 3 fatty acid for human health. Because rates above 15% would require rapeseed oil (which has a high proportion of omega 6), inclusion of algae into aqua feed above this rate would cause relative fatty acid ratios between omega 3 and omega 6 increase in the latter's favour, which would undo some of the health benefits.
In all, fish fillet DHA levels 60% of those found in fish with full fishmeal inclusion in their aqua feed could be achieved. Furthermore, the algae provided protein in optimal amino acid ratios for fish growth, increased digestibility and contained vitamins, along with antioxidant carotenoids and other beneficial compounds not found in fishmeal.
Yeast-derived carbs, organic trace minerals improve survival, immunity, feed conversion efficiency
Similarly, yeast-derived protein and its by-products were also found to be a partial fishmeal substitute that provides essential protein amino acids. By increasing the maturity fish size of salmon and sea bream by 10%, yeast protein essentially counteracted the impact of reducing fishmeal inclusion from 49% to 5%, which had caused the fish's final size to fall by a tenth.
Furthermore, it also boosted feed conversion ratios by 5% and 17% in sea bass and Atlantic salmon respectively, while reducing salmon mortality by up to 60% (at maximum inclusion rates). The latter helps to counteract the higher mortality rates commonly seen at low fishmeal inclusion levels.
Nor was protein the only fishmeal substitute that could be derived from yeast: Fractional carbohydrates (FCO) isolated from cell walls of yeast cells resulted in better immunity and improved liver cellular structure and function. By increasing the intestinal villi's absorptive surface area, better nutritional uptake and improved feed conversion ratios resulted. Along with enhancing the digestibility of plant-based aqua feed ingredients, the addition of yeast fractional carbohydrates also increased skin mucous production, thereby providing the fish enhanced protection from environmental pathogens and irritants.
The latter could also explain why when exposed to vibrio alginolyticus, salmon with yeast-derived had rates of infection ranging from 0% to 8.3% (depending on the inclusion rate), versus 33% of fish in the control group. Along with superior protection from a better mucous protection, the addition of yeast derived fractional carbohydrates also boosted phagocytic (a type of white cell) activity by 50% relative to the control group.
Finally, the addition of organic trace minerals such as iron at a 200ppm concentration resulted in anywhere from 50% to 80% fewer gaps in the flesh of salmon fillet grown with minimal 5% fishmeal inclusion than in the control group.
Still a long way to go, but it's a start!
In closing, it must be said that while all the above findings are hopeful, these findings are still in their early experimental stage. They are years away from becoming mainstream substitutes.
Moreover, not only do none of the above means do away with our need for fishmeal, which would be the most ideal solution. Even the above solution, at its best, leaves us with feed that contains too much DHA, not enough EPA and perhaps lacking some essential fishmeal ingredient that today's science may have overlooked.
Moreover, with the current shortage of fishmeal in the world, on the basis of nutritional differences and appearance, one could still undertake niche marketing, whereby wild catch carnivorous fish fetch the highest price. After them, farmed fish with conventional fishmeal inclusions would command an intermediate price while those raised on minimal fishmeal would have the lowest market value, particularly among educated, high-income western consumers.
Clearly, when aquaculture experts worry about how the fishmeal deficit could undermine not just fish performance but human health, much more research still needs to be done.
While fishmeal remains too rich an ingredient for a singular 'magic bullet' solution, the latest findings demonstrate that when alternative ingredients derived from yeast and algae are combined with organic trace minerals, a significant part of the fish performance gap and sea food nutritional deficits created by inadequate fishmeal inclusion can be avoided.
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