Cattle mostly eat what humans can’t digest — grasses, not grains. That energy would go to “waste” otherwise. And the water consumption stats often include rain water (“green water”).
And since lands with grass is limited by space, and seasonality, we also do grow a lot of food for them.
E.G: UK stats for 2015/16 of soy imports (3.1 million tonnes) break down:
- 1.1 million tonnes for livestock
- 1.42 million tones for human food
- 0.58 for non-foo products