His owner Helen Macdonald asked for a copy of the post-mortem examination after Geronimo was culled by Government officials despite protests.
Preliminary findings of the post-mortem examination were enclosed in a letter to the owner from the Government Legal Department, her lawyers said.
Veterinary surgeons supporting Ms Macdonald reviewed the findings.
In a statement, the lawyers said: “As reviewed by Dr Iain McGill and Dr Bob Broadbent, the preliminary gross post-mortem findings are negative for visible lesions typical of Bovine Tuberculosis.
“For clarity there are no white or cream caseous, enlarged abscesses typical for bTB in alpacas whether in the lungs, bronchial, mediastinal or retropharyngeal lymph nodes.
“Ms Macdonald has formally requested the full findings of the post-mortem report ‘Form TB50’, together with all relevant documents and the results of further tests on tissue samples, blood, serum or plasma taken or obtained from Geronimo, along with any further test results including Enferplex, Idexx, Actiphage and any other PCR or interferon gamma tests performed by Defra, along with the results of histopathogical examination.
“She has further requested that both fresh, frozen and formalin fixed tissue and fluid samples be preserved and provided to an independent expert to carry out further tests.”
In a statement, Chief Veterinary Officer Dr Christine Middlemiss 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.”
Geronimo had lived happily at Ms Macdonald’s farm in South Gloucestershire.
Surrounded by supporters outside Defra’s Westminster offices, Ms Macdonald said: “We urge the Government to act with compassion and cooperation, which to date has been severely lacking, creating deep and unnecessary distress to Geronimo.
“We call on the secretary of state to tender his resignation immediately.”