Animal agriculture uses a disproportionate amount of water, not only for keeping the animals alive but also for growing the crops to feed the animals.
water isn't destroyed by being used for animals to eat or drink. even if it were (which makes no sense and, again, is not true), using water to make food is a good use for water. additionally, myopically focusing on any single metric really harms our understanding of the system as a whole. for instance, cows are fed cottonseed, but cotton isn't grown for cottonseed: it's a waste product. why should the crop weight of cottonseed be calculated as a portion of the water use of cows, when that's a conservation of resources? it shouldn't. this metric is a red herring.