The deceased, Pehlu Khan, and three others were beaten up by the vigilantes on Saturday while they were transporting cows in six vehicles to Haryana.
The victims were admitted to a hospital where Khan died on Monday night. The postmortem was conducted yesterday, SHO Behror, Ramesh Sinsinwar, said.
A case was registered against the assailants but no arrest has been made so far, he said.
In Jaipur, Rajasthan Home Minister Gulab Chand Kataria said that though the smuggling of cows for slaughter is prohibited in the state, no one has the right to take the law into their hands.