I have several friends that use bladders from the American bison/buffalo for water containers - but only for historical demonstrations. They can work well with proper preparation and care, but are too fragile for most things. You have to treat them a lot like you would a childs's baloon filled with water. When they are wet, pliable, and filled with water, most any sharp object will cut/tear them.
Their use would be more for just around a stationary camp than for carrying water on the trail. The American Indians used them that way. They were brought out and used in camp, but packed away empty when moving or on the trail.
To use them? Wash thoroughly, then tie off all the extra "openings" except for one. Then make a wood spout for the bladder - drilled through with a stopper, and have a groove around the outside of your spout. Then slip the bladder up over the sides of the spout and tie around it tight - in the groove. Also tie on one or more extra loops of cord around the spout - to use to hold/hang your water bladder with. When not in use, your bladder will dry out. So you will need to "soak" it in water to get it soft and flexible when you want to use it next time. If you start to get a little "off" taste in the water, wash out your bladder with a little baking soda added. Some small tears can be carefully sewn up, but it will be hard to seal the tear and around the stitches. And it will naturally "sweat" or seep a little water through the bladder itself - just like using a canvas water bag.
My friend gets about a dozen uses/weekends out of one - he does Living History demonstrations. Then it gets too fragile, or developes hard spots that won't soften with soaking, or he cuts it on a twig or drops it and it breaks. But he does get around a dozen different sessions of use out of one - sometimes more, sometimes less.
The larger animals have larger bladders - which make larger containers. But larger bladders also then hold more water which weighs more - putting more strain/stress on the bladder. So there are trade-offs. My one friend uses buffalo bladders because that is what a number of people wrote in their journals in the late 1700's around the western end of the Great Lakes. That is his Historical Documentation for them for his demonstrations.
The idea is old, and appealing for it's historical past, but does have some pretty severe limitations.
Of course, these are but my humble thoughts to share. Take them as such.
Mike Ameling