Am seriously thinking about breeding with my 17mth old chocolate labrador but have heard several theories that the dog can change dramatically after going with a bitch. changes described are things such as the dog becoming more territorial, temperament changes, dominance, obidience and generally becoming more and more difficult to controll. If somebody could shed some light on this for me I would be very gratefull.

i've heard that it depends on the dog to weather it not it changes them
has yours got all the releent halth checks done.
i'm sure someone will come and give you more info about behaviour change

Well mine never really changed still as gormless as ever.All my boys havent changed at all.If anyone changesI personally think its the girls (not all of them)they become very mature and quiet down in my experience

Well mine never really changed still as gormless as ever.All my boys havent changed at all.If anyone changesI personally think its the girls (not all of them)they become very mature and quiet down in my experience but it culd be different in labs i have no clue about them,except they look sweet.

Some do,some don't but unfortunately you don't know till the deed is done and then theres no going back.
You also need to ask yourself are you able and willing to be equally responsible for the pups if they are returned and also the bitch comes to the dog for the mating-have you got suitable facilities.
Archer