Milk containers as opposed to clear plastic bottles can be a menace on your plot. After a while they disintegrate and you find yourself having to pick hundreds of bits of them out of the soil.
The clear ones even outside last for years. I have a 5ltr one I brought back from Spain in 1999 and it has nurtured a courgette every year since.
I normally use bottles in the spring to protect the plants, until they poke out the tip, I like the though of protecting the cobs. Something has been chewing mine.
We have a thief but they come armed with a knife, I know when they go because I tend to break things off rather than risk leaving a knife about the place. So they do not chew the cobs in situ so I presume it is the deer.