There is no way the vet and zoo aren't concerned at this point. I've seen a few either contractions or calf movements, but nothing like I have seen. I can see her udders now when she turns a certain way. I am like others have mentioned, worried for April and the calf or calves. I keep praying all will be OK. I've never seen an animal in active contractions for this long without progress. Cows hide their labor as does most animals, because they are ALL considered at risk during labor and delivery for predators. Horses are preyed upon as well.
How long has she been doing the mannequin stance? Seems like at least a week. I remember mentioning it before. And NOW they say that stance is contractions? Well, no animal should be having that strong contractions for a week.
I wonder if anyone from that zoo has contacted other zoos yet? Even the zoo April was at prior and gave birth, to see what her pregnancy and labor was like there? For those interested in the vet, google him. Timothy Slater I believe is his name. Country Vets in NY. I don't see anything in his write up that states he has been the vet for a zoo before. It said he was overseer, and a school teacher, works with farm animals, and small animals.