The pot does 20 birds, and based on the assumption that they will each eat about a kilo in a weeks treatment, works out at about 75p per bird per weeks treatment, plus the cost of the pellets you would have to provide to feed them. If you buy the 10kg bag, it will, cost about £1 per bird for the drug + feed all in, so works out cheaper, but may not be quite enough for a full dose for each of them, - I'm not sure what ducks eat compared with chickens.
I would have thought that the difference is pretty marginal for a relatively small number of birds, and what you save on buying 20 kilos ready treated could be lost if the feed was out of date and had to be thrown away by the next time. Whereas the 10kilos might not be quite enough, so you would need a pot of powder anyway to be sure of finishing the job effectively. I've never found any problems with mixing my own, using ordinary care, and I can make what I need, when I need it, and know it has been properly mixed and is in fresh food. I have more faith in my own ability to measure the correct amount and mix it thoroughly, than to rely on the commercial mixing process where a very large batch is mechanically stirred and may not always be evenly distributed, who knows?
