Nerfs: Requires Mill before they can be constructed. Khitans: Shepherds and Herders generate +5% food. Additional 10 seconds for construction time. So build time will be 28 seconds, instead of 18. This is somewhat countered since two villagers will be reseeding the Pasture anyway.
Buff the civ in some other way if too much of a nerf.
Pastures don’t need drop off sites. The last much longer than farms.
Pasture civ bonuses for civs in the future if given. One for each civ only. 50% faster Pasture creation time. Pasture have 40 extra food. Pasture provide 5 population space.