A photo of thin cattle being transported on a Cook Strait ferry has sparked an investigation by the Ministry of Primary Industries.

The cows, which were transported from Picton to Wellington last Sunday , March 8, were photographed by a concerned passenger.

The passenger's friend, Anne Robson, then posted the photo to Facebook where it has been shared more than 8500 times and has prompted comments about animal cruelty.

Heagney Bros co-owner Peter Heagney said the cattle were in the right condition to be transported.

"In our opinion we were carting quite fit cattle that were in the right condition to be carted to the works.

"There is nothing wrong with them. If the stock was not fit, it won't go on the truck."

That call was made by the farmers, but some responsibility fell on them, Heagney said.

The cows were not from Marlborough, Heagney said.

Marlborough Federated Farmers president Greg Harris said while he did not know the full situation, it reiterated his earlier comments that underweight stock were being sold and killed.

However, the cattle on the ferry were not emaciated, he said.

"I think they still have a reasonable coat and fat cover.

"But the reality is, some of the cattle at the moment are lean and it's better for them to go to the works than to leave them on the farm."

Some farmers did not have enough food for their cattle and were sending them to the meatworks earlier than usual as a result of the dry conditions, he said.

"I can understand people's concerns about the light animals but people need to realise there are light animals on a few farms because of the drought.

"I don't now the exact situation here but it's not unusual for them to be a bit lean."

Ministry of Primary Industries senior communications adviser Jim Flack could not comment of the details of the investigation as the information would be subjudice if the case ended up in court.

However, Flack said MPI received 700 animal welfare complaints a year in relation to farm animals. Most of those complaints related to stock in poor condition.

He could not give any indication how long the investigation would take.

In cases like this, the farmer and the transport company could both be charged, Flack said.

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