Feeding catfish liver

[sequoiacat]

Is it a bad idea to feed my catfish some diced up liver, that is meant for people to eat?

[Bas Pels]

There are 3 reasons why I would not do this

1 liver for Humane consumption is from a mammal - thus warm blooded. Fish have a lot of problems digesting this, as their body temperature is far less then the mammal had. Some fishes can digest mammals, but not the unspecialized ones

2 a liver has 2 functions in a living body: to detoxify harmfull substances, it changes them or stores them. If you feed your fish liver with a lot of stored stuff, this will hurt it

3 livers, as all organs, are very vunerable to decay. eating rotten food is, apart for specialized animals, a bad idea

You will appreciate 2 & 3 also apply for humans. I might, therefore, be somewhat biassed

[sequoiacat]

Glad I checked.

So what organs of other fish can I feed to my catfish?

Also would small whole frozen fish, thawed to room temp and fed raw be good to feed my catfish?

Which catfish would be speacialized in eating mammal parts?

[MatsP]

There are 3 reasons why I would not do this

1 liver for Humane consumption is from a mammal - thus warm blooded. Fish have a lot of problems digesting this, as their body temperature is far less then the mammal had. Some fishes can digest mammals, but not the unspecialized ones

This makes sense in the case of fats. Beef liver has about 4 percent fat. Liver is not muscle tissue from a warm blooded animal either, it's softer, more easy to digest.

2 a liver has 2 functions in a living body: to detoxify harmfull substances, it changes them or stores them. If you feed your fish liver with a lot of stored stuff, this will hurt it

I agree with this, although the "store it" is a last resort, and for most liver you get in the shops, it comes from young animals (veal, chicken, lamb). Use in moderation, and you'll be fine.

3 livers, as all organs, are very vunerable to decay. eating rotten food is, apart for specialized animals, a bad idea

Sure, if it looks like it's been dead a long time, don't eat it, and don't feed it to the fish either.

Michael Hardman, who works at University of Helsinki, and spoke at the Catfish Study Group Conference a few months ago, says that liver sends fish absolutely crazy, and is a good "flavour" to add to home-made food. I do believe he's clever enough to know the potential dangers too.

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Mats

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Mats

[sequoiacat]

Thanks mats, I'll use it as a treat and flavor enhancer.

[racoll]

1 liver for Humane consumption is from a mammal - thus warm blooded. Fish have a lot of problems digesting this, as their body temperature is far less then the mammal had. Some fishes can digest mammals, but not the unspecialized ones

Ah, the good old saturated animal fat in fishfood question. I think I contest this opinion every time it's brought up!

I wrote a short article in PFK on this; maybe it will be published in the September issue?

Essentially, there is very little scientific evidence that feeding animal fats and proteins is as bad is people make out*. Fish are able to use saturated fats just as well as unsaturated fats, even in really quite cold water.

I see no reason why liver can't be used as a occasional, say weekly supplement, or as a small proportion of a staple food.

livers, as all organs, are very vunerable to decay. eating rotten food is, apart for specialized animals, a bad idea

I don't think this precludes its use entirely. Just make sure it is fit for human consumption and stored carefully.

*This is not to say feeding only beef to a Panaque or Otocinclus for example, is a good idea.

[Mike_Noren]

Essentially, there is very little scientific evidence that feeding animal fats and proteins is as bad is people make out*. Fish are able to use saturated fats just as well as unsaturated fats, even in really quite cold water.

I don't doubt you, but I have a question: if I feed fresh ground beef to my fish, even meat-eaters like my cichlids, they invariably get white stringy feces (what I think of as "fish diarrhea"). If it isn't the mammalian fat... what causes it?

I don't think this precludes its use entirely. Just make sure it is fit for human consumption and stored carefully.

*This is not to say feeding only beef to a Panaque or Otocinclus for example, is a good idea.

I agree. After many unintentional trial & errors I've come to the conclusion that spoiled food is the real cause of bloat and fish death, not the foodstuff in itself.

[Bas Pels]

1 liver for Humane consumption is from a mammal - thus warm blooded. Fish have a lot of problems digesting this, as their body temperature is far less then the mammal had. Some fishes can digest mammals, but not the unspecialized ones

Ah, the good old saturated animal fat in fishfood question. I think I contest this opinion every time it's brought up!

I wrote a short article in PFK on this; maybe it will be published in the September issue?

Actually, I was not thinking of saturated fats, but the cellmembranes

These membranes are something between solid and liquid in a living organism, and these are around the fats which are to be digested.

Obviously I did not read your article - although I will be curious when it is published, but I wonder, did you do the eventual experiments with purigfied fats and proteins or with whole cells? You will agree using purified fats and proteins does not inform about eventual problems with the cellmembranes

[racoll]

if I feed fresh ground beef to my fish, even meat-eaters like my c*****ds, they invariably get white stringy feces (what I think of as "fish diarrhea"). If it isn't the mammalian fat... what causes it?

Even lean beef mince is pretty high in fat, probably richer in fat than the fishes are able to handle, saturated or unsaturated.

Perhaps just the quantity of fat might have been the problem here. Try feeding them something with vegetable fats at a similar proportion, and see what that does?

I wonder, did you do the eventual experiments with purigfied fats and proteins or with whole cells

I didn't do any experiments, just did a review of the literature. I guess they used processed fats and proteins.

You will agree using purified fats and proteins does not inform about eventual problems with the cellmembranes

I didn't realise there was much of a difference between animal and plant cell membranes. What are the details?

[Bas Pels]

If you start with a technical membrane - that is a lot of polar groups, with 2 apolar tails, which makes vesicles and so on, a living cell has, in this membrane, a lot of proteins to contact the surroundings. You know this.

If you go from a plant cell to a mammal cell, a lot of further stuff is added - such as cholesterol - to keep the membrane on the correct level of fluidity - not too much, not too little. I studied chemistry, a book such as The Cell, which is used for graduating students for their biochemistry courses would provide all you need. I understand you work at a university, in biology, so it might be easy to contact a colleague who teaches biochemistry

Racoll, you migfht have noticed that in winter your hands don't mouve so easily - this is because your cellmembranes in your hand are a bit less fluid than they should. Nothing to worry about, but this is precisely what happens when warm blooded meat is eaten by a fish @ say 25 C. Obviously, @ 32 C (amazon temperature) the problems will be much smaller

[racoll]

I'm sure there is a undergrad text lying around somewhere. I'll have read.

Not sure how it relates to ability to digest though.