Irrigation systems don't use potable tap water; they use rainwater, or ditches, or in some cases wells. None of these consume marketed energy at anything like the rate given above for tap water. (Wells often need water pumps, but the energy use of the pump is tiny compared to a municipal potable water system.)
This may well be. But at least in the case of the diary farmers that surrounded my home town, all the water used to grow the cattle feed fell from the sky.
I assume most of the water needed to sustain cows is spent on the plants they eat.