noun
A feeding trough for livestock, especially horses or cattle. The word is straightforward and neutral.
See also: 秣
馬がまぐさ桶から干し草を食べている。
The horse is eating hay from the manger.
飼い葉桶 is a more general term for a feed trough, while まぐさ桶 specifically refers to a manger for dried grass or hay (秣).
Compound of まぐさ (秣, 'fodder, hay') and 桶 (おけ, 'bucket, tub'). The kanji spellings reflect the components literally.