I'm playing on a custom modpack with TiConstruct and Lycanite's Mobs (2 more fluids). I had an emerald fluid cow, which I milked. I accidentally placed an emerald bucket on the cow, and it died. I thought fluid cows weren't supposed to die to their own fluid...?
Edit: I just lost my gold fluid cow as well. Since there's no command to spawn them in, this is really annoying.
Edit 2: I discovered that the fluid appears to not be in the bucket (after harvested from cow), and when you try to place it, it doesn't place. However, when you attempt to milk the cow again, it places the bucket and kills the cow.
Okay, I'm redoing this with new information.
Cows will somehow die to their own fluid, despite you saying they won't.
Buckets will pretend that they do not have fluid in them, and will only show they have fluid in them when right clicking on a cow to milk it. This only happens with buckets milking MooFluids cows. The only way to save my cows has been to stack multiple empty buckets, as that makes them normal again.
Old Post:
Okay, I'm redoing this with new information.