Are the pellets joined to each other with mucous? If so, this indicates that the pig is dehydrated.
If each pellet is individually formed they can have a "tail", it looks like a piece of cotton thread.
I have never directly associated this with any untoward condition. However, it could, possibly, be any early sign of dehydration. Try increasing the amount of moist food, eg cucumbers, melons etc, for a day or two and see if there is any mprovement.