"Farmers I've spoken to ... we're all just aghast; we don't operate like that."
Mr Engel says there are codes of welfare in place for treatment of "bobby calves" -- which are often bought by independent operators and reared for beef.
"It's not acceptable."
Other calves which go straight to slaughter are still not treated in this way by any farmers he knows, Mr Engel said.
"They have them in sheltered pens."
However footage of dead calves piled up ready for collection are less of a concern, Mr Engel said,
"That's just the reality of farming -- not the cruelty part, but that farming is cruel ... they can die."
"A lot of things on farms the public don't need to see," Mr Engel said.
"Animals do die and people come to collect them; that's another industry."
Some of the footage showed the behaviour of transport operators and a slaughterhouse employee, which is outside direct farmer control, Mr Engel said.
Mr Engel is also critical of the way the footage was collected -- describing the hidden cameras as a "trespass" -- and of calls to boycott the industry simply because of the failure of the Ministry of Primary Industries (MPI) to investigate.
"To threaten the whole industry, that just means there's another agenda."
The footage had been given to the Ministry for Primary Industries (MPI) by the animal welfare group Farmwatch on September 14, but the slaughterhouse featured, Down Cow, said they had not been contacted by the ministry.
Mr Engel also draws a distinction between the bobby calf industry, which is "well regulated" -- with guidelines and rules including the requirement for ear tags, and the calves in the footage which were "sickly animals going to the pet food industry".
"Nobody's had much regard for them anywhere along the chain as it's only pet food," Mr Engel said.
"But it's not acceptable."