Organiser Shane Bird say he underwent surgery after dislocating his hip and chipping a bone. It's hoped he will be on crutches today.
"He's one of the top cowboys in the country - he's not someone who usually hurts himself," a rodeo insider said today.
"They take huge risks but they are as tough as they come."
Mr Bird said while bull riding is a dangerous sport, Gallagher was unlucky to be injured.
"It wasn't like the bull was being malicious - in fact, he's one of our quieter bulls. It was just unfortunate that he got in the wrong place at the wrong time," Mr Bird said today.
"There was no obvious break, no bone poking out, it was all hidden under the skin.
"But he was saying straight away that he thought he'd dislocated his hip, just with the way it felt."
The New Zealand Rodeo Cowboys Association has a provident fund set up to give injured cowboys financial support.