There is a role for substituting culturally equivalent terms to communicate biblical truths but the opening post suggestion ['pig' for 'lamb'] is inherently problematic.
Here's some snippets from an interesting article relating a similar translation difficulty
Wycliffe CEO Explains Importance of 'Unconditional Love' in Bible Translation [LINK]
Wycliffe Bible Translators CEO and President Bob Creson in a recent letter revealed the true story of teaching the Hdi people of West Africa the word for God's unconditional love, a moment which forever changed the dynamic within the community for the better.
…the Hdi people had a word for temporary love and conditional love in their native tongue, they lacked a word for unconditional love, a term which explains one of the main tenants of the Christian faith.
Creson added that the word for unconditional love, whether it is found or created in a language, is the only one appropriate for "that deep love," the one which explains "the extent to which God would go for one person."
By learning such words as unconditional love, along with the full translation of the Bible, communities around the world change both spiritually and practically, according to Creson. "The scriptures transform lives […] we see people's lives change dramatically," Creson said, adding that once the Bible is translated for a society, moral issues such as prostitution, anger management, and armed robbery tend to decrease dramatically.
The translation of the New Testament section of the bible for the Mbam cluster languages of West Africa has been completed, and will be dedicated at the end of 2013.
Rob