This is an example of a noun (animal) pre-modifying another noun (conservation).
Well, sometimes we have to consider how nouns function within a larger noun phrase.
Well, animal is a noun, and conservation is a noun, but together they form a noun phrase: animal conservation.
So what's the problem then?
Well, in this example, the main noun is conservation.
What do you mean main noun?
Well, in this example, are you saying that zoos are good for animals or good for conservation?
Right, so conservation is the main noun.
I see, so what's wrong with animals?
OK, well in the example animals is pre-modifying conservation. 'Pre' means 'before' - the word animals comes before the word conservation, right?
Wait. Did you say modifying? What's that?!
Well, the word animals changes (modifies) the word conservation - it tells us exactly what kind of conservation.
OK. But I still don't see what is wrong with the original sentence.
The problem is.. If you use a countable noun to pre-modify another noun, then that modifying noun (in this case animal) must be singular.
I see. Like computer scientist?