Changing dog food can cause an upset stomach in your Golden Retriever, and this can lead to diarrhea.
This applies to puppies that may have been raised on a different brand than you plan to use, and it also applies to older dogs that you have decided to switch from what you have been feeding them, to something different.
If for any reason you do need to switch to another brand of kibble, make the change over to the new brand slowly.
Add a little bit of the new chow to the old, gradually.
On the first day of switching brands, make the mix about 1/4 of the new kibble, and 3/4 of the old kind.
Every day add a bit more of the new kibble, while lessening the old.
You should be able to switch completely over in about a week, and by changing it slowly, your Golden will not have an upset stomach this way.
If you bought a new puppy, you should have been given some of the food that she has been eating.
This should be enough to use while you combine it with the new brand you will be changing to.
If there is a medical reason or any other valid reason in which you need to make a quicker switch over (such as a momma giving birth to puppies and needing to go on puppy food), then do a 50/50 mix for 2 or 3 days to help lessen any side effects.