The Ministry for Primary Industries is investigating after a bull was found dead days after competing in a rodeo.
MPI received the complaint from an advocacy group, Anti Rodeo Action NZ, last week.
The group's spokesperson, Lynn Charlton, said they saw the death had been posted on social media.
She said it was important the cause of death was established.
"We think the New Zealand public would like to know that, given he was not a bull that's just in this paddock happily munching away."
She said the bull had competed in the most recent rodeo season including Waimarino rodeo, a two-day rodeo, nine days before it was found dead under a tree.
A spokesperson for MPI said it received the report a week ago and would speak to the bull's owner and contractor.
New Zealand Rodeo Cowboys Association president Lyal Cocks said he had been made aware of the investigation but could not comment until the findings were available.
He said he had no knowledge as to why the bull had died.
The bull’s owner Jonny Ward said the bull was 12 years old and was being treated by a vet for an illness.
“I love these bulls… I’ve got nothing to hide.”
He said he not been contacted by MPI but was happy to comply with an investigation.