I've been feeding my neps a few drops of milk in each pitcher for a couple weeks now by way of experiment. *I have done no controls, but the new pitcher the N. campanulata put out is encouraging:
The digestive juices in the campanulata pitcher are very viscous! *It's almost like karo syrup or something.
I have noticed that the milk will accelerate pitcher death, but that may be true of any feeding in the species i've noticed it with. *Be careful not to get milk on the pitcher itself, or it will cause problems.