Soybean meal and soy protein concentrate in fish feed, good, bad? It all depends it seems.

[HenryC]

There's much debate in the aquarium hobby regarding soy ingredients in fish feed. Some people will tell you it's bad, others it is good, but that's it, seems everything is anecdotal experience right? 

I found this paper, hosted in a University of Mexico (UNAL) by a Chinese scientist in the Netherlands, Dr. Yueming Dersjant-Li, you can check her profile here: http://animalnutrition.dupont.com/eventsinsights/contributors/dr-yueming-dersjant-li/

Her qualifications are legit it seems! Here's the paper on soy products regarding to fish nutrition: https://www.uanl.mx/utilerias/nutricion_acuicola/VI/archivos/A34.pdf

If you ever wanted to know if Soy products in fish food is good or bad, I urge you to read it. If you dn't want to read the entire paper though, I can summarize some of the most important stuff I took from it:
 

 

1. The rapid growth of aquaculture coupled with the relative high prices of fish meal and other marine animal proteins made food manufacturers to look for safe alternatives to replace part of these meals with plant alternatives.
    
2. Among plant protein ingredients, soybean meal is considered as the most nutritive plant protein source. However, the high concentration of anti nutritional factors limited the inclusion levels of soybean meal in aquafeed. In soy protein concentrate, the anti nutritional components are eliminated. Compared to fishmeal, soy protein concentrate has advantage of high protein and amino acids digestibility co-efficiency, readily available and consistent quality. seems Soy Protein Concentrate is much, much better than Soybean Meal, because of the anti nutritional components are eliminated (more on that up next).
    
3. Literature studies demonstrate that soy protein concentrate is a good alternative to fishmeal in shrimp and fish diets. In shrimp diet, 40% of fish meal can be replaced by soy protein concentrate without negative influence on growth performance. In fish, 40-100% of fishmeal can be replaced by soy protein concentrate. In conclusion, soy protein concentrate is a good protein source for aquafeeds.
    
4. Soybean meal (SBM) is considered as the most nutritive plant ingredients widely used in pig, poultry and fish feed. Among plant protein ingredients, soybean meal has well balanced amino acid profile. Furthermore, SBM has the advantage of being resistant to oxidation and spoilage and is naturally clean from organisms such as fungi, viruses and bacteria that are harmful to shrimp and fish. SBM can be used to partially replace fish meal or animal protein in fish and shrimp diets. In general, however, at high replacement levels the growth rates of fish and shrimp are reduced. The growth depression effect of soybean meal at high inclusion levels may be related to the antinutritional components presented in SBM. It has been observed in many fish species that anti-nutritional components in SBM, such as trypsin inhibitor, antigens, lectins, saponins and oligosaccharides, can have negative effect on digestibility of nutrients and performance of fish.
    
5. The amino acid profile in fish meal in general reflects dietary amino acids requirement of fish. Compared to fish meal, soy protein concentrate (SPC) has balanced amino acids profile. Assuming using SPC as sole protein source in fish feed, the essential amino acids provided by SPC meet very well the dietary requirement of channel catfish, common carp and tilapia. For rainbow trout, methionine concentration in the diet may need to be balanced by other protein ingredients or synthetic amino acid.
    
6. The anti-nutritional components have been removed during the processing procedure of SPC. Consequently using SPC as protein source will assure a healthier animal and better growth performance of fish compared to using soybean meal as protein source in fish and shrimp diets. Literature studies showed that 40-100% of dietary protein from fish meal could be replaced by soy protein concentrate (SPC) without negative influence on growth performance. Whereas replacing fishmeal by soybean meal (SBM) or soy flour at high inclusion levels, in general, reduced growth rate.
    
7. The replacement of fish meal by SPC can have also positive effect on environment. It was observed that inclusion of SPC in the diet reduced P losses and improved P retention in trout and in salmon. Trout fed soybean meal diet had reduced fecal dry matter content, indicating diarrhoea. Whereas the trout fed SPC diet had constantly high fecal dry matter content. These studies demonstrate that soy protein concentrate can be used as a good alternative protein source as replacement of fish meal in fish feed and as replacement of marine animal protein in shrimp feed.
    
8. In fish, SBM may be used to partially replace fish meal in the diets. However, high inclusion level (>30%) of SBM could cause intestinal damage and in general reduce growth performance in different fish species. It appears that carnivorous fish species such as salmon and trout are more sensitive to the anti-nutritional components in SBM than herbivorous or omnivorous species such as carp. In general, however, soy protein concentrate has been proved to have better nutritional value and produced better growth performance in fish compared to soybean meal.
    
9. When using soy protein to replace fish meal or marine animal protein, the nutritional balance in the diet should be considered, including amino acids, fatty acids, energy and minerals. Fish meal and marine animal protein meals generally contain more fat and minerals than soy protein. At high soy protein inclusion levels, a mineral supplementation is recommended. Phosphorous is the most critical mineral when formulating fish feeds which contain a high level of soy protein.
    
10. To achieve a balanced nutritional composition in fish feed, a more divers choice should be made in selecting feed ingredients. A mixture of feed ingredients will provide more balanced nutrients than only use limited feed ingredients to formulate fish feed. In conclusion, soy protein concentrate can be used as an excellent protein source for fish and shrimp diets, as alternative to fish meal and marine animal protein meal.

So, any thoughts guys? What I got from it is that:
Soybean Meal = Seems to be bad in big quantities and in carnivorous fish, no matter the other ingredients. Inferior to SPC. 
Soy Protein Concentrate = Overall really good, nutritional and near perfect replacement for fish meal.

We also have to take in consideration the percentage of soy that is used. Something could contain soybean meal (kinda bad) but onl;y in 10-15% concentration, so that wouldn't be that bad. I wish they would disclose the percentages of each ingredient, but I guess that's asking too much of manufacturers right? 

Also, this study was made with fish like salmon and tilapia, not your standard neon tetra, oscar or angelfish, but I guess they cannot be that different?

Thoughts?
 

[Cory]

Interesting study. I'd say there could be huge differences between coldwater fish such as salmon and tilapia vs tropical fish. Metabolisms of fish can be very different.

I also like to put things into perspective for myself. Lets say we are focusing on the merits of soy protein vs other protein sources. Meanwhile most hobbyist aquariums are doing much more damage with random meds, overdosing dechlor, elevated stress levels, leaching chemicals from decorations, stray electrical currents from devices, no seasonality to water temperature etc. 

For some reason hobbyists have taken to food as one of the most important things. While it certainly is important, lots of other factors are equally important. From my observations in Peru as an example, fish rarely eat the same thing twice for the most part. Day one could be a decomposing fish. Next day is algae, day after that is rotting fruit that fell into the water. Day after that is a live fish etc.

Now I'd say none of that analyzed the way it was in this study would look good either. However the combination of all those micro and macro nutrients actually becomes a better food source. 

I personally always care of the food is received by the fish first. Then the effects on the fish's digestive tract, then by how clean it feeds in my aquarium. 

If I ever magically got the time to study fish food, I would focus on the fiber contents of fish food. Protein seems to be plentiful and a bunch of difference sources. However the fiber and ease of digestibility seems to vary quite a bit in foods I've fed. 

I'd say my experiences with fish food have always been. I've yet to find a food that when my fish ate and I kept fresh, didn't grow the fish well, and keep them healthy.  I've definitely found foods that fish don't want to eat, or don't have enough fiber and easily constipate fish. I've never noticed my fish being fat from hit fat percentages, only overfeeding. 

I have seen fat and protein levels make a difference in turtle egg production and fat storage for turtles. This could be relational the way I keep turtles vs fish as these are only my observations. 

I have found some foods to help color enhance, some to help provide calcium, some with more fat for fry production in livebearers. I haven't seen the source of protein make a difference however whether it was wheat germ, corn, fish meal, whole fish meal, salmon, herring, krill. 

In my koi, I've actually seen less protein, more wheat lead to bigger fish growth in a season. The wheat germ has more fiber/easier to process and thus the fish ate more food. This lead to more cleaning of my pond which I am not fond of, but I think there are so many levels to pull with our hobby that optimizing becomes personal choice really.

In a fish farm where you're maximizing profit, these food studies can make sense. You aren't worried about the longevity of a fish, simply taste and weight growth. So much so, to bring it back to salmon, I believe farm raised salmon has their flesh dyed before sold because with the farm raised diet it would be white/tan instead?

[Ryan W]

Like you said, the article is driven towards game and commercial fish. Meaning, its fish that will eventually be consumed by humans. So, it's not so much "will this sustain a fish?" as it is "what are the affects on humans that eat these fish?". Not only is soy extremely high in estrogen, its also one of the most traded goods on the planet. if DuPont can sell more soy, they are going to find a way. Selling to fish farms in massive bulk loads can create a lot of revenue for whoever holds significant soy interests, say a company like DuPont. Again, this being based off of commercial fish. Is it a good thing? Well, I don't work for Dow so I cant help there. I do live 25 miles from it though.

As far as our aquarium fish go, as a hobbyist, I wonder what the affects of all that estrogen packed soy could do to breeding operations for certain species. Since soy can and does raise estrogen levels in male species, how would estrogen affect hobby fish sustainability? Would feeding soy based fish foods be detrimental to the male/female ratio? Would males even be able to fertilize eggs long term? Here's a quick article I found interesting https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3921986/. Although the article references a synthetic estrogen found in oral contraceptives (birth control), it can still produce the same affects of biological estrogen.

Also, Cory is correct about dying farm raised salmon pink. Their flesh just doesn't produce enough enzymes to correlate with wild caught salmon. Why? Because of the food they are fed at the farm. Also like Cory said, in a fish farm where you're maximizing profit, these food studies can make sense. I guess the real question is what are the consequences of consuming commercially raised fish solely based on taste and weight? It's when those practices are prioritized over the welfare of those fish and the people consuming them when it becomes a problem. Circling back to DuPont...