You need to aim to have 5 of each animal from the start
there are many people who think that they only need to collect 1 to pass their level
ie if they are on Noah's Ark 1 + 1 = 2
but if you see the animals on feed you should adopt them.
Adopting an animal does not stop some one else being able to adopt it
the only limit on feed animals is the time you have to adopt it
there is no limit to the amount of people who can adopt from each posting.
If you see 5 posted collect all 5 - you might not be stuck if you don't.
as you will need a total of 5 each to pass eventually.
Feed animals add value to your zoo
and if you dont breed them you do not need to upgrade cages.
Concentrate on breeding the non feed animals
as these take a long time to breed
and the cost of upgrading cages to
release babies can break the bank.
If you are having problems getting your posts to postlooks like the post is hanging then try this
right click in the middle of the blank post where you
would normally click post and choose reload