The Boeing 737-300 aircraft, registered PK-MBP, operated by Merpati Nusantara Airline, departed from Sentani Airport, Jayapura, Papua, to Mopah Airport Merauke. The Merauke air traffic controller reported that when the aircraft was on final approach there were no obstructions on the runway, so he cleared the aircraft to land on runway 16. During the landing roll, the pilot observed that a cow had entered the active runway and was running across the runway in front of the aircraft. When the aircraft was about 1,000 meters from the runway 16 threshold, the left engine struck the cow. The pilots stopped the aircraft on the runway and shut down the left engine. The cabin crew informed the pilots that left engine cowling was damaged. The aircraft’s occupants were not injured, and disembarked from the aircraft unaided, using air stairs at the apron. The investigation found that the airport did not meet the requirements of ICAO Annex 14, Volume 1, Paragraph 9.10.2, Standard, or the intent of Civil Aviation Safety Regulation (CASR) 139 Subparts 4.2 and 4.12. The airport perimeter was not fenced, and there was no other appropriate means of preventing animals, large enough to be a hazard to aircraft from entering the aircraft movement area of the airport.