I'd def go with the recommendations @casportpony has given both can be given orally @CayugaJana gives it to hers over peas or mealworms just enough of the treat that they gobble it right down, so since your using other niacin why don't you just give the liquid to this one duckling unless your other Pekins might need it too. It def won't hurt any of them what their body doesn't use will be peed out.
