As I was sitting watching the havan being performed, there was a big commotion outside. When the priests saw what it was, they were quite pleased. We’ve had cows visit, but never a bull so this was a unique occurance.
Each of the gods has an animal that they ride on, called a vahana. For Vishnu it is an eagle, for Agni (fire) it is a goat, for Lakshmi she is represented by a milk cow, and Shiva rides a bull named Nandi.
The appearance of a bull while a yagya is being performed is regarded as an excellent omen (nimitta), that the god is pleased and has come to accept the offerings and bless the participants.
As a practical matter, the bull wandered in and then realized that he couldn’t turn around. The ghee lady, who has considerable experience with cows, used some word (bha) to make him back up, which he did.
That is, until he knocked over a can of yellow dal, and decided to stop for a snack.
Then he continued to back up until he had room to turn around.
These guys are big and muscular but very calm. I would not want one angry with me though. They are powerful animals.
And he was on his way.