I mentioned dairy cows because they happen to have a similar count to horses. We talk here about animal sourced food, which includes dairy. Dairy has all the fat soluble vitamins, if you have your cornflakes with dairy milk you increase the vitamin content enormously

Noting that beef cattle typically live in places where nothing people can eat will grow, so if we stopped eating them the land would be abandoned and would instead support the same biomass of just as thirsty, just as methane producing (but with no one invested in fixing the methane problem) grass eating animals, be they wild horses or deer or bison.

Meanwhile how much water do pet dogs and cats consume? How much extra is wasted by being in open containers in airconditioned spaces?

I like that you only found fault in the fun fact that dairy and horses have similar numbers, which you didn't deny, and the fact that the water they drink isn't wasted which you reckon takes too long but it has been going on for a very long time, it has to be in a steady state in natural grasslands. Before beef it was bison in America