Oh! You can feed up to 20% of a bird's diet in duckweed. Here is a FAO website that gives general info on nutrient content
http://www.fao.org/ag/AGA/AGAP/FRG/lrrd/lrrd7/1/3.htm
In a nutshell it has 15 to 25% protein, more or less and about 40% fiber. It is really, really easy to grow and people have come up with a variety of innovative feeding systems. I lack innovation overall and embrace plodding efficiency and cheapness. I feed in a standard feed pan. I got my duckweed on eBay after having read reviews of who was a good seller of viable duckweed. I think I spent $15 or $20 for a gallon ziploc bag. I have two sturdy plastic storage boxes and two kiddie wading pools and I feed about a dishpan a day from each container. I feed it with my spent hops or whatever chicken feed I have at the time. I also feed it to my sheep and goats mixed with their grain and they eat it without hesitation. It has probably reduced my feed bills by a quarter to a third.
It's easy to grow. I threw a handful of fresh poo in each container, filled with water, and added the duckweed. I think I waited about two weeks initially before I harvested with a strainer. I have also put in mosquito dunks (bt) in each container and have had no issues with Mosquitos. It's easy and the ducks go crazy for it.
I live on a property with natural water sources. I am being very careful not to accidentally introduce it into our waterways.
I am going to be investing in a bigger wading pool so I can feed more to the goats and sheep. Easy peasy.
Karen