no, it's not. milk at 2 tablespoons per gallon is a decent fix for a calcium deficiency. but, you should never use it if you can provide an alternate source, ie, cal/mag, or molasses and epsom salt.
I know this thread is old, but just in case anyone else was wondering, you can feed your plants whey from milk. I make my own yogurt and cheeses and end up with a ton of whey. I didn't want to just dump it so I was looking up ways to use it and found it's good for plants. http://www.gardenguides.com/107407-use-whey-watering-plants.html