Japanese cats go "nyaa nyaa", or sometimes "nyaa-o" ("neeyow" isn't usual). The Japanese word for fart is "onara"; "he" (with short "e") is not an elegant word and should be avoided in normal conversation.

These sites collect or discuss onomatopoetic animal sounds.

(1) Sounds of the World's Animals

(2) Chit-Chat Among Japanese Farm Animals

(3) Onomatopoetic Words in Japan

(4) Nâ Kani o nâ Holoholona -- Animal Sounds (Hawaiian)

(5) Talking Like Animals -- Sapanish Language

(6) Animal Sounds: Onomatopoeia in Hindi (Note--written in Japanese; Code Shift to JIS)

~Masato