If this is vet prescription Thiamine, I dosed a 50lb pygmy buck with 2 cc's every 6 hours... you should also dose with Pen G at a rate of 1cc per 10 lbs every 6 hours as well because Listeria has the same symptoms as Polio.
If that is what you have to treat him, very high doses are needed to counteract the neurological symptoms that occur with polio.... I successfully treated a 5 month old, 35 pound doeling with 12cc's split into 2 doses for 2 different injection sites every 6 hours...after the first injection the symptoms showed improvement
I agree with whats been said....at 100 mg of Thiamine in your B complex, 4 1/2 cc per 100# is needed so at 15 pounds so 2 -3 cc should be good...every 4-6 hours..if he has polio then after the first few shots you should see improvment..if not suspct listeriosis http://www.tennesseemeatgoats.com/articles2/listeriosis.html
This link has a chart on how much Penicillin is needed per his size...