This has been reported before and finally came to a conclusion (http://beatmag.com/daily/latest-news/buleleng-man-has-intimate-encounter-with-cow.html):
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Buleleng Man Has Intimate Encounter with Cow
The village of Sangsit in the Sawan subdistrict of Buleleng, was the scene of a very strange ceremony yesterday, with most of the residents taking part in the drowning of a cow.
The reason behind this bizarre ritual stems from a 25 year old local man who was caught copulating with a female cow. The scandal has caused a furore amongst villagers, and prompted a special meeting to discuss how to deal with it. 'We agree that this is an unfortunate event in our village. Therefore, it's our obligation to cleanse the village with a ceremony,' said the head of the village, Made Subakti.
As part of the ceremony, the cow was decorated with yellow and white cloth in a scene not unlike a wedding ceremony. After that, the cow was herded into a boat and disposed of into the sea. The man was asked only to dispose of his clothes.
The ceremony cost around Rp 40 million, and had participation from most of the villagers. The man did not have to pay due to his lack of funds. 'This incident is a natural cycle, not a purpose. This indeed has to be accepted as the fate of our village,' stated Jro Gede Segara, one of the local traditional elders.