I have just booked my Newfoundland George in at Easter time. He will be 14 months. My breeder told me I shouldn't think about desexing till at leat 12-18 months, something about it being a big risk to be put under anesthetic while they are still growing?
Having him entire up until now has not been problematic, he doesn't seem all that interested in bitches, and as far as making some escape attempts, he rarely leaves his spot sleeping at the backdoor to explore the rest of his (huge) yard, let alone knock down fences to go flirting!
I'd love to hear more info on desexing big breeds.