January 23, 2017
Plant-based salmon feed: Health problems for fish, and for people too?
By ERIC J. BROOKS
An eFeedLink Hot Topic
- The peaking and decline of world fishmeal production has brought the proportion of salmon feed accounted for by fishmeal from 60% to under 20%
- Plant-based feed inputs create salmon farming performance issues but researchers are adapting plant-based feeds to salmon physiology
- Skyrocketing plant-based feed inclusion rates are destroying the essential fatty acid levels and ratios that make cold water fish like salmon a healthier protein source than livestock-based proteins
- Rising health consciousness will force producers to differentiate their production into more premium high omega 3 fat and conventionally raised fish lines
For many years, declining fishmeal production and skyrocketing aquaculture output have cast a shadow over fish farming's sustainability. Until now, the industry has coped with this situation better than expected, and focused on animal productivity. Now however, new studies and falling fishmeal inclusion rates are second-guessing the nutritional claims of fish being healthier than protein from land animals.
From 2000 through 2012 inclusive, world aquaculture production rose 133% (from 15 to 35 million tonnes). By comparison, the amount of fish oil used in aquaculture remained constant while fishmeal production fell by over 50%.
According to fishmeal market analyst Jean-Francois Mittaine, from the 1.5 to 2.0 million tonne levels once taken for granted, Peru's fishmeal output fell 27%, from 864,400 tonnes in 2015 to an estimated 631,000 tonnes in 2016. At 4.09 million tonnes, world fishmeal production is back at its mid-1970s output level. By comparison, aquaculture production, which was 6 million tonnes in 1975, will total approximately 80 million tonnes today.
With aquaculture and Peruvian pelagic stocks going in boldly opposing directions, fishmeal's price rose from approximately US$450/tonne in the year 2000 into the US$1,500 to US$2,000/tonne range since 2010. With fishmeal often unavailable at any price, the primary challenge has been to find alternative, plant-based feed sources with comparable protein digestibility. This is especially true for carnivorous fish species such as salmon, whose digestive systems are not adapted to absorbing protein from plant-based inputs.
Partly by using key enzymes to make soymeal and rapeseed meal more digestible, partly by only providing omega 3-rich fish oil early in salmon's life cycle (when it is required for proper physical growth), salmon feed's fishmeal inclusion rates have plunged. From up to 66% in the 1980s to 55% in 1995, fishmeal comprised 42% of salmon feed by 2000 and 35% by 2005. Salmon feed fishmeal inclusion rates then fell to 27% by 2010 and 20% by 2015, with some feed suppliers lowering its inclusion to 15%.
Aside from the difficulty salmon digestive systems have in accessing plant-based nutritionals, the omega 3 fatty acid found in plant-based feed materials is not appropriate for salmon growth. Instead of being rich in EPA and DHA like fishmeal, the omega 3 fat in rapeseed oil for example, is mostly in the form of alpha linoleic acid (ALA).
Salmon fry are not capable of converting ALA into the EPA and DHA they need for proper skeletal development. Both soymeal and rapeseed meal contain high levels of omega 6 fatty acids. Salmonids are not used to such high omega 6 fat levels in nature. Moreover, their high concentration has also been implicated in an array of human health problems too.
According to Alltech aquaculture nutrition consultant Ionnis Nengas, the substation of plant inputs in place of fishmeal resulted in, "High fibre and high antinutritional ingredient challenges, along with fatty acid deficiencies and indigestible plant based feed components." Among the problems created by the substitution of plant-based inputs in place of fishmeal included, "Impairment of the fish gut structure, skeletal deformation and lower flesh quality."
Indeed, the higher rates enteritis and weaker immune systems of salmon raised on high levels of plant-based feed ingredients could account for the rising number of disease losses suffered by both Chilean and Norwegian salmon growers in recent years. 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.
The good news is that over time, by carefully adjusting feed formulations, adding necessary enzymes and supplementing key omega 3 fatty acids at key growth phases, the industry is overcoming these problems. Hence, the proportion of salmon feed accounted for by plant-based ingredients has risen from less than a third in the 1980s to approximately half by 2000 and 80% today.
The bad news is that while we can minimize the impact of plant-based feeds on salmon growth, salmon flesh's own nutritional characteristics are being altered. It carries deep implications for human health and ultimately, the way omega 3 fat rich farmed fish are raised and marketed.
According to a study headed by Stirling University, researcher Dr. Douglas Tocher ("Impact of sustainable feeds on omega-3 long-chain fatty acid levels in farmed Atlantic salmon, 2006–2015", M. Sprague, J.R. Dick and D.R. Tocher, 22 Feb 2016), the amount of omega 3 fat per 100g in Scottish farmed salmon has fallen by 50% over a mere five years.
From 2.9g /100g of omega fat (1.5g DHA +1.4EPA) in 2000, the omega 3 fat level in farmed salmon fell to 2.8g/100g (1.4gDHA+1.4gEPA) by 2006. It then fell slightly to 2.6g/100g (1.4gDHA+1.2gEPA) by 2010, just as fishmeal's price began skyrocketing.
After 2010 fishmeal's price touched US$2,000/tonne and its supply plunged to the lowest level seen in decades. Consequently, salmon feed fishmeal inclusion rates plunged –and with it, the omega 3 fat content of salmon.
By 2015, the Stirling University study found Scottish farmed salmon omega 3 fat levels had plunged to 1.3g/100g (0.7DHA+0.6EPA), approximately half the level of five years earlier and at least 60% lower than the level seen in farmed salmon in the early 1990s. From containing more omega 3 fat than wild catch, farmed Atlantic salmon now contains nearly a third less.
In an interview with BBC News ("Omega-3 oils in farmed salmon 'halve in five years' ", 16 Oct. 2016), Dr. Tocher stated, "About five years ago, a portion of [Scottish] Atlantic salmon of 130g was able to deliver … our weekly recommended intake. Now, the level of omega-3 has halved."
Moreover, with Norwegian salmon making up most of the world market, their lower fishmeal inclusion rates imply that most farmed salmon may have even lower omega 3 fat levels than what the Scottish study estimated.
Oddly enough, despite its negative marketing connotations, one implication of this study's finding is that people should consume twice as much salmon as before. With omega 3 fat levels in farmed fish plunging, Tocher concluded that governments need to revise their guidelines for consumption of omega 3 fat seafood like salmon: "At the moment, they are advising to eat two portions of fish per week - one of which should be oily." With salmon only containing half as much omega 3 fat as before, "The advice of one portion of oily fish [per week] really should now be two portions at least."
Despite the short-term stimulatory impact consuming additional fish could have, the overall marketing message is a negative one for two other reasons. First, with the minimization and variance in salmon feed fishmeal levels comes great uncertainty about exactly how much omega 3 fat consumers are receiving.
For example, according to a 2015 study by America's National Institute of Health, the omega 3 fat of farm raised salmon surveyed ranged from 0.72g/100g to 1.53mg/100 grams, a difference of over 100%. Without the assurance that they will be receiving the omega 3 fat they expect, this creates a salmon marketing problem, particularly among educated, well informed, higher income consumers.
Second, not only has the total amount of omega 3 fat fallen inside farmed fish but just as importantly, their omega 6 fat content is also increasing. According to scientific research, the ratio of omega 3: omega 6 in one's omega 3 fat source is as important as the overall omega 3 fat level itself.
Protein with a high omega 3: omega 6 ratio allows the human body to more efficiently absorb omega 3 fats from salmon compared to the same quantity of omega 3 fat from enriched eggs, which have a higher omega 6 fat level. This however, may no longer be the case.
In nature, a 1990 study by van Vliet and Katan (American Journal of Clinical Nutrition, 51:1-2) found that wild caught salmon had a omega 3: omega 6 fat ratio of 11:1, whereas farmed salmon had a markedly lower 6:1 ratio. This was in the days when salmon feed fishmeal inclusion rates were above 50% and the long decline in fishmeal supplies started.
Initially, farm-raised salmon made up for their lower omega 3: omega 6 ratios of between 3:1 and 2:1 by having higher overall omega 3 fat levels than wild salmon. After staying above 6:1 through the year 2000, farmed salmon's omega 3: omega 6 ratio fell to near 5:1 by 2006. After 2010, even as omega 3 fat levels plunged, the amount of omega 6 fat in salmon doubled over five years.
By 2010 as fishmeal started being used more sparingly, farmed salmon's omega 3: omega 6 ratio fell to 3.3:1. Based on the Stirling University study, today's farmed salmon omega 3: omega 6 fat ratio of 1.3:1 is barely a tenth of the ratio one still finds in wild caught salmon.
As the proportion of salmon feed with plant-based meals increases, so does the omega 6 level in salmon protein. It is very possible that in the future, it will no longer be scientifically accurate to call salmon or other farmed seafood 'healthier' than livestock derived proteins. This will further dent the ability to market farmed seafood that has already been victimized by a slew of sustainability issues and food safety concerns.
The good news is that on the distant horizon, a solution is on its way: The Canadian government recently approved an Alltech manufactured, omega 3-rich feed product (All-G Rich) made from algae that has been approved by the Canadian Food Inspection Agency (CFIA) for use in swine diets. It is soon expected to be included in Canadian hog feed. Nikki Putnam, a registered dietitian nutritionist with Alltech notes that this new product line has the capability to boost omega 3 levels across all protein lines, noting that, "This is a unique opportunity to make healthy foods, like meat, eggs and dairy, even healthier," Putnam says.
Alltech general manager Stuart McGregor adds that, "There is a growing niche market for enriched foods—like omega-3 eggs," he says. "There is also a growing demand for sustainability." If all goes well and it boosts Canadian pork's omega 3 fat levels, there is no reason this new omega 3 fat source could not be incorporated into salmon feed.
It will however, probably entail a significant boosting of farmed salmon production costs –and that implies that salmon farming will soon have to change its business model. Right now, the industry is putting its best face on the worldwide attention these revelations received, stating that the omega 3 fat levels in salmon still greatly exceed guidelines.
With omega 3:6 ratios already in ruins and omega 3 fat levels destined to fall more in the future, that reply will not fool upmarket, educated consumers for long.
The omega 3 fat advantage that farmed seafood has over livestock protein is evaporating. Consumer awareness that the premium one pays for eating salmon will not offer significant levels of heart-healthy fats is growing. The industry must get around this problem by de-commoditizing salmon into regular fare and more premium fillets that have been fed omega 3 rich feed. The sooner the industry adapts to this emerging salmon and human health issue, the better.
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