The closest I could find is 1-1/2 teaspoon per gallon of water for the 400-800mg treatment level in treating air sac infection caused by MG/MS and E Coli. Mix a fresh solution daily. Administer 7-14 days, not to be used more than 14 consecutive days. It must be the sole source of water for chickens to drink. There is no withdrawal.
This package weighs 280 grams
Package contains 102.4 grams oxytetracycline
102.4 / 280 = 0.37 , which means that it's 37% oxytetracycline and 63% filler
370 mg per gram
One teaspoon probably weighs 3 grams, so it's 3 x 370mg = 1110 mg per teaspoon The 800 mg dose for one gallon = ~3/4 teaspoons