The Protein Pyramid
Feed compounders and animal nutritionists should take a second, hard look at fish meal processing and utilization for animal feeds. The facts and figures are overwhelming: All fish species used for fish meal and fish oil in both the Pacific and the Atlantic are very important for the marine ecosystem, as they prey for fish, birds and mammals. Increased exploitation of these species to meet the demands from an expanding fish farm industry could very well turn out to be an ecological time bomb.
The November 10, 2008 editorial of The New York Times titled “The Protein Pyramid” is quite alarming, and must be borne in mind when using fish meal as an animal protein source in aquafeeds and monogastric rations. Here it is:
“Per capita meat consumption more than doubled over the past half-century as the global economy expanded. It is expected to double again by 2050. Which raises the question, what does all that meat eat before it becomes meat?
“Increasingly the answer is very small fish harvested from the ocean and ground into meal and pressed into oil. According to a new report by scientists from the University of British Columbia and financed by the Pew Institute for Ocean Science, 37 percent by weight of all fish taken from the ocean is forage fish: small fish like sardines and menhaden. Nearly half of that is fed to fanned fish; most of the rest is fed to pigs and poultry.
“The problem is that forage fish are the feedstock of marine mammals and birds, and larger species of fish. In other words, farmed fish, pigs and poultry — and the humans who eat them — are competing for food directly with aquatic species that depend on those forage for their existence. It’s as if humans were swimming in schools in the ocean out-eating every other species.
“The case is worse than that. When it comes to farmed fish, there is a net protein loss: it takes three pounds (1.36 kg) of fish feed to produce one pound (0.45 kg) of farmed salmon. This protein pyramid of small fish fed to farmed fish, pigs and poultry that are then fed to humans is unsustainable. It threatens the foundation of oceanic life.”
“The report’s authors suggest that it would be better if humans ate these small fish, as many cultures once did, instead of using them as feed. That is one way of addressing the problem of’ net protein loss. The real answers are support for sustainable agriculture in the developing world and encouraging healthy, less meat-based eating habits as a true sign of affluence everywhere.”
ALTERNATIVE PROTEIN SOURCES NEEDED
Animal proteins such as poultry byproducts and meat and bone meal have been used to replace fish meal ‘in fish feed. Animal proteins are good protein sources with low price, which can be used to partially replace fish meal. However, due to the occurrence of Bovine Spongiform Encephalopathy (BSE), commonly known as Mad Cow Disease (MCD), consumers are questioning feeding practices based on the use of animal proteins a$ raw materials in animal feed. In some countries, animal proteins are banned in animal feed.
Therefore, alternative sources for fish meal and fish oil must be considered. There are several examples, according to the American Soybean Association (ASA), where fish meal and fish oil in feeds for carnivorous species can be totally or substantially replaced by alternative protein and oil sources. Fish oil can be substituted by plant oil, a method that has already been developed, or the fish feed can be produced from plant or zooplankton.
Soybean meal (SBM) is considered to be one of the most suitable and economical candidates for replacing fish meal in commercial aquafeeds. It has been identified as having the best essential amino acid (EAA) profile of all protein-rich plant feedstuffs for meeting the essential amino acid requirements of fish (Lovell, 1991). On the negative side, the sulfur-containing amino acids methionine and cystine are generally considered to be most limiting in soybean products compared to the quantitative amino acid requirements of most fish species (NRC, 1993). However, the presence of antinutritional factors (ANFs) limits the use of soybean in crude and processed forms in aquafeeds.
ANTI NUTRITIONAL FACTORS
Raw or non-heated soybeans contain a number of heat-labile ANFs that inhibit some digestive processes of fish when replacing high dietary levels of fish meal with soybean meal (Refstie et al., 1998).
Thus, proper heat treatment of soybeans is important to inactivate the anti-nutritional factors without affecting their nutritional quality of soybeans for these to be optimally used in aquafeeds.
SBM can be used as a total or partial protein source for farmed tilapia, depending on fish species, size, dietary protein level. SBM source, and processing methods. For example, processed solvent extracted SBM, with or without methionine supplementation, successfully replaced up to 5% of fish meal in the diet of Nile tilapia fry (O. mossambicus) and 67% in the case of tilapia hybrids. Supplementing SBM with the deficient EAA did not improve fish growth, and therefore was proven unnecessary.
Milkfish (Chanos chanos) is a popular and economically important food fish in Southeast Asia, including the Philippines. Shiau et al (1988) examined the feasibility of using soybean meal at the level of 0%, 33%, 67% and 100% replacement offish meal as a protein source for milkfish feeds containing 30% and 40% protein. Methionine was added to the SBM containing diets to ensure adequate dietary levels of this amino acid. The diets were each fed to three groups of juvenile milkfish (initial size 4 grams) for eight weeks, and at the end of which time the apparent digestibility coefficients for protein and dry matter were determined.
After eight weeks, there was a trend to lower growth and poorer feed efficiency in diets containing more than 33% soybean meal replacement of fish meal, but there were no significant differences for growth or feed efficiency among the treatments containing 67% or less of soybean meal, at either 30%o or 40% total dietary protein levels.
The digestibility of the diets was unaffected by the level of soybean meal replacement of fish meal, indicating that these two ingredients (SBM and FM) have similar biological availability.
NuPro, a functional protein from yeast, manufactured by a proprietary Alltech process, is also worth considering for pig, poultry, ruminant, and aquaculture feeds. The potential of NuPro in pet food industry is tremendous. It contains highly concentrated levels of essential and functional nutrients which are important in the diets of young animals. NuPro is rich in nucleotides, glutamic acid for palatability, inositol, amino acids, and peptides.
The possibility of replacing traditional protein sources (fish and soybean meals) in tilapia feeds with NuPro has been successful, according to Suzi Fraser of the Aquafeed.com.
Tilapia were fed for eight weeks with formulated diets using graded levels of NuPro (0%-100%) in place of SBM, and were examined afterwards. Irrespective of level of dietary inclusion, fish fed NuPro-containing diets outperformed tilapia fed a commercial diet.
Weight gain in tilapia fed with diets containing NuPro ranged from 319%-458%, whereas the weight gain of tilapia fed with commercial feed is 27%. However, the commercial feed returned better feed conversions.
Graded replacement of SBM with NuPro resulted in superior (P<0.05) performance at NuPro levels of 20%, 40%, and 80%. When NuPro served as the only protein source, no difference was observed in weight gain compared to animals fed with control and commercial diets.
NuPro significantly reduces muscle lipid levels in the edible portions of the fish, which provide a leaner and potentially healthier product for the marketplace. A reduction in hepatic lipid levels may also be beneficial to the health status of cultured tilapia.
NuPro must be formulated and mixed into the feed or premix at the production/mill level and not topdressed.