Ummar Khan's family had earlier stopped cooperating with the administration to conduct the autopsy to pressurize the police to crack down on the alleged cow vigilantes who killed him.
"We are disappointed and disheartened... Somebody from the government could have met us for assurance at least," said Razzak Khan, Ummar's uncle, adding that they were giving their consent for the autopsy too.
The 42-year-old father of eight was bringing home cows he had bought when he was attacked and shot dead, says the family, which belongs to the Meo community of farmers and cattle-owners and lives near the Rajasthan-Haryana border. Ummar Khan's two relatives were also attacked - Javed Khan and Tahir Khan.
Ummar Khan's body was found on a railway track 12 hours from the spot where the police seized an abandoned pick-up truck with six cows - one dead and the others with their feet and mouth tied. The tyres of the truck had been removed.
His killing revived memories of a dairy owner, Pehlu Khan, who was beaten to death on suspicion of cattle smuggling and Bihar Chief Minister Nitish Kumar declared in Patna on Monday, that he has had a detailed discussion with Prime Minister Narendra Modi on cow vigilantism. "He was of the opinion that the law should take its own course and that we should deal sternly with those elements,' Mr Kumar told reporters.
"We have no such word in our vocabulary as gau rakshaks," said Rahul Prakash, the Alwar district police chief. "They were criminals and this is a murder case," he added.
But the police insist that this wasn't the first time that Ummar Khan and Tahir had been accused of smuggling cows under a law enacted to prevent their slaughter.
Ummar Khan had at least one case registered against him while Tahir, who escaped with injuries, had about half-a-dozen cases, Mr Prakash said.