Will Falconer, DVM Moderator
Tumors have perhaps been the commonest side effect, Karen, some coming sooner, some later.
You may want to try transfer factors rather than crude colostrum, most of which is too large to be absorbed (antibodies, useful to the calf in the first 24 hours of life, worthless to other species except as expensive protein). Transfer factors are the immune boosting fraction that counts, and this product I use in my cancer patients has those concentrated 80:1: TF Canine Complete. In my cancer patients, I'll also add the human version, called TF Plus Tri-Factor Formula.
My dosing protocols are in my free ebook called Insider Immune Protocols, available to my Pack members as a download (no cost to sign up for the Vital Animal Pack, either) All the best with your GSD. As you might be aware, surgery, while life saving in a case like this, doesn't deeply address the cancerous state. Minimally, I'd be charging up his immune system most efficiently from now on, to prevent recurrence.