As a man of science you certainly are choosing to ignore the science that IS available. Or do you consider the information, and links to real science, performed by real scientists, and printed in peer reviewed journals in post #23 to simply be anecdotal? Do we also ignore Heiko's findings, a man who has spent more time studying discus in the wild than any other person on this planet?
I completely agree with you that the area of ornamental fish nutrition is not very well researched, but in many cases there is enough research out there if you know where to look, or have performed your own controlled in-house studies, and in many cases that research can be extrapolated to cover many species.
And as far as NLS, I didn't initially mention any brand of commercial pellets as I didn't want this to become another food brand argument, my reasoning for posting those photos was simply to demonstrate the results that one can see when using only pellets as a source of nutrients, and there being no need to use mammal meat in order to get healthy growth in a Discus. I honestly don't know what the results might be from feeding other pellets exclusively, nor do I know anyone that does, hence the reason for listing the brand in that comment. Fair enough? So let's please move on from the NLS vs the world part of this discussion, that was not my intention or goal in this thread.
Back to the science etc - Here's what we do know with regards to fatty acids, lipid accumulation, and fish.
We know that many accredited scientists have spoken out against the use of mammal meat in the diet of fish. The reasoning has always been the same; ""The routine of feeding beef heart and other red meats to Cichlids can ultimately give rise to health problems. Poultry meat is also suspect. Red meats, including lean meats such as beef heart, contain the wrong sorts of fats - these harden within the cold-blooded fish, leading to blockages and fatty deposits around the liver."
We also now know that in the wild, discus are NOT a highly carnivorous species that require massive amounts of protein or fat for proper growth. Certainly, young juvenile discus require protein in the range of 45-50%, but that could be said about pretty much every juvenile cichlid kept in captivity, including those classified as herbivorous, nothing newsworthy there. But as a cichlid begins to mature, their nutrient requirements in captivity change due to metabolic changes within the fish, and as this metabolic change takes place, so does their high demand for both protein & lipids.
How does a fish such as that suddenly become an eater of beef? A fish that in the wild consumes; vegetable matter, algae & micro algae, aquatic invertebrates, detritus, and terrestrial & arboreal arthropods, has somehow over the years become an eater of mammal flesh & fat? Seriously?
Do you really need long term feed trials to prove otherwise, or should common sense simply apply here? The reality is that no one is going to ever fund the type research required to commit a lab to long term feed trials (as in several years), because no one in the industry cares how long a discus lives in captivity. That type of real hard science, with real hard data, will never exist.
Chong et al ran a 3 month feed trial on juvenile discus (fish approx. 4.5 grams in weight) and concluded that a diet consisting of 45-50% protein, and 8% fat was ideal for optimum growth for juveniles of this species. I have no argument with those stats, and again the same could be said for hundreds/thousands of other ornamental species, but somehow this data has been used by certain segments of the discus camp to support their use of a high protein "beefheart" diet. WTH? Where's the science in that?
Chong et al used fish meal as the source of protein (along with casein & gelatine as binding agents) in their study, not beefheart.
I'm as old as dirt, and this certainly isn't my first rodeo regarding this subject.
Beef heart was originally used (back in the 50's) by collectors/importers of discus for a few different reasons.
1. It was a cheap, easily sourced form of food that was high in protein.
At that time everyone believed that Discus were carnivores, which up until just a few yrs ago was still commonly believed by many discus keepers, and probably still is by many today. Many online profiles still list them as just that;
http://www.cichlid-forum.com/profiles/species.php?id=227
2. It was readily accepted by most wild discus.
3. At that time (back in the 50's) there were no premium commercial fish foods available, none. Fish foods on a whole were low quality, high starch, formulas, just as dog foods were back in that period. (and unfortunately some still are today) At that time even I would have used beef heart as a main feed as the "science" was non-existent, and alternative options were extremely limited, especially if one was breeding in large numbers such as Jack Wattley was. But as previously stated, even Jack no longer promotes the use of beef heart & this is a man who has seen & done it all when it comes to collecting, breeding, and keeping discus in captivity.
BTW - I'm curious, how many people do you personally know that have fed beefheart heavily to their discus, and managed to keep the fish alive for 10+ yrs? I personally don't know any. One of the admin on simplydiscus (Al) once told me that for tank raised discus, 4-5 yrs is the average lifespan. I actually questioned him on this a number of yrs back when they posted a poll on their site. And of course, the vast majority of those that posted in the poll did in fact feed some type of beef heart mix. Anecdotal evidence, perhaps, perhaps not. While I understand that tank raised discus have the potential to live 10-15 yrs (or longer) in captivity, I don't believe that I would consider it normal for a fish that is heavily fed beefheart to survive that long. IMO an average lifespan of 4-5 yrs for a discus kept in captivity is downright pathetic. I don't care how many ribbons or trophies that fish may have claimed in its short existence.
I'm not saying that longevity can't be achieved, or hasn't been, while feeding a large quantity of beef heart on a regular basis for years, just that I wouldn't consider it a typical scenario. While I understand that you have not been personally promoting the use of beef heart in an exclusive manner, you did just state that "many do without any issues". You sure about that? The data available (while very limited) tends to suggest otherwise.
No one has to be an expert on nutrition, or be a criminal attorney to weigh these things out in their own mind, and draw their own reasonable conclusions based on a preponderance of the evidence. To date, I have yet to hear or read about anyone that specializes in the health & nutrition area of aquatics to suggest that beef heart is an optimum form of food for any species of fish, carnivorous or otherwise.
While we may never have an real hard data, from long term feed trials (involving discus or otherwise) what we do have is a number of MSc, Ph.D., holding scientists that specialize in the health & disease in fish, that have spoken out against its use in feeding long lived fish, including cichlids, such as discus. Their reasoning for this is based on decades of studying & working within the nutritional scientific area of ornamental fish, not just personal opinions, and unlike breeders, importers, exporters, or winners of NADA events, there are no personal monetary gains, motives, or agendas, involved.
I think I've said about as much as can be said on this subject. To the OP, best of luck with whatever you decide.
Cheers!
