"..they typically produce 5 mg daily..." Maybe you meant 5 grams, not mg.
Also, animals make their own ascorbate in their liver and it goes directly into the blood, not ingested through the stomach. The ascorbate from liver contains positive ions Mg, Ca, Na, K. So, the best answer I've come up with is formulate liquid Vit. C that is not the acid form of ascorbic acid, but rather is a solution of Mg, Sr, K, and Na salts of ascorbic acid.
I'm all good on vitamin C. What I have trouble getting enough of , is Vitamin G.