It depends on what you are going to do during your visit. If you just want to have a look, watch zero to one show/performance/feeding, then one day can be fine. If you like to take a lot of pictures too, then spend at least 2 days (There is - afaik - a cheapter 2-day-pass).
Ok, so if I'm going to the Loire valley for 5 days and seeing 3 chateaux, I should spend two days at the zoo, considering I am insanely keen on taking photos there and I want to see al, the species well?
Any zoo the size of Beauval is worth 2 consecutive days if the weather is favourable and you like photography. Then again, depending on when you are going, the longer summer opening hours might be enough for one day ... i'd still go two if I could and the weather was nice.
Should I go up to hippos, lions, cheetahs, savanna and big cats first, or down to elephants, pandas, wolves, bears and apes?
Also, are there any species that haven't been sighted for a long time and you would like me to try and find?
When I went a couple of years ago, the Giant panda male was only really active at talk/feeding times, but that's the direction I headed at opening. I didn't know at the time, but the female was pregnant, giving birth a few days later. While waiting for the giant panda though, it's easy to nip around to see the tree kangaroos, koala, clouded leopards, red pandas, snow leopards ........ Maybe if you do go the two days, attend the feeds/talks on the first and work out what you could catch up with on the second day.
I rarely attend shows to be honest, but sometimes it's the only chance to see some species. However, the bird display is a must.
Yep. But keep in mind that this region not only has wonderful castles but also very good zoos beside Beauval. E. g.: Bioparc Doué la Fontaine and Parc Animalier Haute Touche in Obterre (for ungulates especially, although hard to get there without a car) and a little more away La Boissière du Dore and La Flèche.
Would they not be happier going to two zoos rather than the same one twice? Depending on where you are staying, i'd certainly recommend La Fleche too.
I definitely had enough time in the zoo with one day last year and saw everything, but could easily spend another day there as well. I'd say visit one day, then decide later whether or not you need another day!
A two day pass is 45 euros though, saving 50% off a second ticket. I don't know if you can upgrade to a 2 day ticket later in the day.
As far as I know you can't. And to @amur leopard : When you have parents with such lack of understanding it is time to look for another mom and dad, isn't it? (Just kidding).
Well, he claims to have a membership there and visit on a regular basis, so theoretically he won't need the pass
