Prime Minister Boris Johnson has described the killing of Geronimo the alpaca as "a tough one" as the animal's owner continues to dispute the decision.
Mr Johnson was asked about the animal - who was put down by Defra at the end of August - at the Conservative Party's annual conference in Manchester.
Geronimo had twice tested positive for bovine tuberculosis (TB) and so the Department of Food, Environment and Rural Affairs (Defra) had ordered him to be euthanised.
But further details from the alpaca's post mortem have been revealed, including a reported lack of lesions in his lungs and respiratory tract, which a veterinary consultant representing owner Helen MacDonald claims show he did not have TB.
Dr Iain McGill said: "There is nothing whatsoever in this histopathology report to suggest infection with M bovis, the causative agent of bovine TB.
"Put another way, if Geronimo had died naturally, and this post mortem had been carried out and yielded these same results, any veterinary surgeon or pathologist would state that there is no evidence of Bovine Tuberculosis (bTB) at all.
"It is important to stress that evaluation of the Ziehl-Neelsen stained sections, which would be expected to pick up any kind of mycobacterial infection including M. bovis, are all negative.”
Speaking to ITV News West Country at the conference in Manchester, the Prime Minister said the priority is stopping the spread of TB.
He said: "I think it was a tough one, it was a very very tough one, in the end you also have to remember that Bovine TB causes huge difficulties and hardships for a great many farmers in the West Country.
"It is not so long ago that people were also contracting tuberculosis through infected milk.
"You have to think about that risk and we have a particular problem with Bovine TB in this country, and it's very sad but we're going to fix it."
In a statement, a Defra spokesperson said: “We have completed the initial post-mortem examination of Geronimo.
“A number of TB-like lesions were found and in line with standard practice these are now undergoing further investigation.
“These tests include the developing of bacteriological cultures from tissue samples which usually takes several months - we would expect to complete the full post-mortem and culture process by the end of the year.”