cju said "As a butcher ,Farmer and a have to know everything type of guy. It is something we have found in all pork where we feed the pigs OATS. YES oats. The reason you see a rainbow in a puddle is because of the oil and water mix.
In pigs fed oats somehow the fat has more liquid , or water in it and it shines a rainbow color. After seeing this phenomenon for 15-20 years and always butcher are own pigs we finally figured it out. Yes I thought it was gone bad a couple of times. even saw it while skinning a pig a few times. started taking notes of what pigs had it and what pigs didn't. That is how we finally figured it out. "
What an interesting fact. We never fed ours oats, so that could be why we never saw it on our own meat.