In the book of Jonah (3:7-8), the king of Nineveh commands city-wide repentance, which included a fast and wearing sackcloth. He not only commands this for the people, but also for the animals.
We commonly read the animals fasting and wearing sacks as humorous and strange, but how common in 8th Century BC was the inclusion of animals in this kind of activity?
Would someone from 750BC Ancient Near East have considered this normal or would they also have thought this was a funny and unusual action? How would they likely have responded in hearing this kind of narrative?
Well, when we speak about this far in time we can not say very much about daily life and rituals of those people.
But Herodotus mentioned something similar that can help us.
Herodotus mentions great Persian commander Masistius that died in combat with Athenians. And after his death Herodotus mentions some strange Persian ritual. He said that Persians shaved their heads and cut the manes of their horses as signs of mourning.
Source: (The Histories, book IX, 23-24)
In this example we can see that is was not odd to use livestock for mourning or some other ritual. I asked this myself long time ago this is what i found, maybe there are some new discoveries on this subject. I hope i helped.