Hi, I am a novice breeder in that my first litter is now only a week and a half old, and I have many questions myself! However, I fed my 4 and a half year old Golden Retriever on Pro Plan Sensitive, without any extra supplements. We did start to give a watered down milk near the end of her pregnancy, and a little cottage cheese now and then, but generally, I was told, if you are feeding a good quality feed then supplementing shouldn't be necessary. I have heard that over-supplementing calcium can cause worse problems than not supplementing. She is very healthy and vet said prior to whelping that she was in very good shape to whelp. Just have her on a good quality diet, and keep up the exercise so her back end doesn't get too big as can cause problems in whelping.
Apologies if you are an experienced breeder and just wondered about supplements! :-s
E