As it stands right now, the goat horn is an unreasonable item, since goats spawn way too rarely, even in the biomes they are supposed to spawn in.

As far as I remember, there are some biome specific settings for spawning, including something like a spawn cost.

So, first evaluate if and how spawning can be affected, and depending on the result increase goat spawning so you're not expected to visit more than 2-3 biomes where they can spawn, or remove the goat horn.