I have a bag that I pack on the back of my bike made with buffalo hide. Very soft and supple, but nothing has ever gotten wet in there, and I have ridden thru some monsoons. I've used it since 2008 and have never treated the leather but it stays looking nice and waterproof.

Have a horse hide holster, tried to break it in for a couploe of months. Gave up. Of course it was treated to be very stiff - and they achieved their goal.

My riding jacke is thick cow hide. Have only gotten rain thru it once or twice, but I do treat it every year to help it repel water.

And that sums up my knowledge, as poor as it is, on the subject.