Better to use a plural form or a single one?

"Liver" as a food substance is an uncountable noun. We treat uncountable nouns as singular. Other examples

- I drink water every day.
- I love to see art at the museum.

If you are talking about individual organs then the word "liver" becomes countable. You would say, "the doctor transplants 30 livers a year." In this case you should use "many" instead of "much". As in "Eating too many cookies, however, would be bad for your health".

In the US you might use livers as countable for chicken livers (I suppose since they are small). But generally when liver is a food substance, we treat it as an uncountable noun. This is not uncommon. I feed chicken to my kids (uncountable). I feed corn to my chickens (countable).

Livers of animals can be plural; liver the item of diet* is non-countable. Thus:

(various mistakes corrected)

The livers of many animals*, like chickens**, geese***, sheep**** etc, can be used as a food. Eating too much liver, however, would be bad for***** your health because liver is rich in****** (or contains much) vitamin A.

* Animals (plural) requires that the animal names be plural.
** The plural of chicken is chickens.
*** The plural of goose is geese.
**** The plural of sheep is sheep.
***** Things can be good or bad for your health.
****** If a food contains much of some ingredient, we can say that it is rich in that ingredient.

I have a goose farm. It has 5000 geese. I can supply 100 livers a day. Goose liver is eaten by gourmets.

Thank you both

You 'are' correct.