YOU SAID:
the horse went to the trough to drink water
INTO JAPANESE
馬は水を飲むために谷に行きました
BACK INTO ENGLISH
The horse went to the valley to drink the water
INTO JAPANESE
馬は水を飲むために谷に行った
BACK INTO ENGLISH
The horse went to the valley to drink the water
That didn't even make that much sense in English.