So, they were faced with a choice when translating the Bible. Make the text totally inaccessible by making up a word for lamb and having to teach about what the animal was before anyone could understand the text or find an equivalent in their culture. They chose the latter.
The only reason that it was problematic was that the animal closest to the lamb in their culture was the pig. In their culture there are two grades of pigs raised: those for consumption and those for sacrifice. The ones raised for sacrifice have to be unblemished and raised in a special way. When those pigs are sacrificed, their blood is understood to provide reconciliation with individuals, the east and the spirit world.
Like I said, it is as close as an animal can come to the significance of the lamb for the Jews and early Christians. Yet, the pig is the opposite of that symbol for the Jews. It is an interesting problem; however, they made the call and translated lambs as pigs. In their translation of the Bible, John 1:29 reads "Behold the pig of God that takes away the sins of the world."
As hard as it is for American eyes to conceive, it is as close an accurate translation to communicate the Gospel to the people of New Guinea as there could be. Wow. Hard.
So, my question for you to consider is this: where is the line? What pieces of your faith are open for translation and contextualization? How far is too far when trying to reach people with the Gospel of Jesus?