Recently leaked film footage showed 21,000 sheep being killed, some of them by being buried alive, The Daily Telegraph in Sydney reported Tuesday.
Gillard made her demands in a meeting with Pakistan Prime Minister Pervez Ashraf in Laos, but she stopped short of endorsing calls by animal rights activists to end the live export trade.
Agriculture Minister Joe Ludwig has claimed the slaughter was "isolated."
Pakistan says the culling was necessary because of health concerns.
Australian sheep ranchers have voluntarily suspended exports to Pakistan and Bahrain pending an investigation.
After meeting with Ashraf, Gillard said she had explained that Australians were concerned about the "graphic and very cruel images" in the footage. She said the Pakistani leader responded that he would investigate.
2014: The Year in Music [PHOTOS]