If it were me id go with the first one: Constrictor's Lab.
The apostrophe shows ownership so its like the snakes lab. I think this would help lead people to not think its a testing lab like Lgray was sayin. Also by having the snakes have "ownership" its like the snakes come first in your business. Which is how it should be, about the animals not money. Just my 2 cents. In the end its your desicion tho!