Hi Sarah-
I’d definitely play it safe and feed your pup as if it is a large breed. There is a good chance she will be if she is 3/4 golden. She is going to be beautiful! Right now, I’d worry more about her joints than cancer. You can always supplement with fish oil or sardines/salmon if you can’t find an appropriate fish based food at this time. I have two three year-old 3/4 lab, 1/4 golden mixes and I give them each one tin of sardines per week and then a krill oil pill each on another day. I also feed them eggs, beef hearts a few times per week with their kibble as well. Good luck and have fun with your pup!
