Green Party animal welfare spokesman Gareth Hughes said the video was a tough watch.
"It's horrific," he said.
"You've got this bull being chased out of the chute, bucking wildly because of the flank strap. It's scared because it's surrounded by people which is technically called ambushing the animal, and as it bucks off the ground you can see it break its leg.
"You can see the incredible pain it's in. It's still trying to flee from the people while having this broken leg.
"It's horrible watching."
What the video highlights, according to Hughes and anti-rodeo activists, is why flank straps should be banned.
Before the 2017 election, the Labour Party said it would rid rodeo of electric prods, flank straps and the use of younger animals.
"I think it's incredibly disappointing we haven't seen previous pre-election promises followed through to end the use of flank straps.
"We've seen animals die under this current government, at rodeos, for sport, for entertainment.
"It's incredibly cruel, and it shouldn't be happening in a modern New Zealand that says it cares about animal welfare."
Damien O'Connor, the Minister for Primary Industries (MPI), did not respond to the issue of why Labour hadn't banned flank straps but said an experienced vet was required to attend all rodeos.
He was confident they were well regulated and generally functioned well.
Rodeo Cowboys Association president Lyal Cocks said the incident shown in the video was "very regrettable" and "very rare".
But it was nothing to do with the flank strap, he said.
That was a piece of harness like any other equestrian sport and it did not hurt the animal, he said.
It just helped the animal to buck in a "more straight and higher fashion".
"MPI doesn't consider there was a conflict of interest in this case," the statement says.
"It's not uncommon, given that rodeo events are often held in rural areas, that a vet may have connections to those competing in or running such events.
"We don't consider that any vets' personal or professional connections to a wider event would put any animals' welfare in jeopardy."
Regarding the cause of death itself, MPI said because the rodeo code hasn't been broken, there is nothing more it can do.
"The investigation didn't reveal that the injury occurred as a result of a breach of a minimum standard or of a breach of the Animal Welfare Act.
"The role of MPI animal welfare inspectors when investigating animal welfare complaints is to impartially apply the relevant legislation that is in force at the time of the incident."