I'm not sure about feeding soaked / sprouted Barley and yes, mash is a complete feed anyway but I had read about Barley recently in one of Victroia Roberts publications. Also, the North Dacota State University website http://www.ag.ndsu.edu/pubs/ansci/swine/eb73w.htm says:
"Poultry, particularly growing chickens, are sensitive to the beta-glucans in barley. Beta-glucans form gels in the digestive tract of birds that are not broken down because of the lack of appropriate enzymes and the rapid rate of passage in poultry. Without addition of beta-glucanases to the feed, barley-based diets have been associated with reduced levels of available energy and with wet droppings, pasty vents, and wet litter.
However, adding beta-glucanases to diets fed to poultry can effectively eliminate the problems with wet, gummy droppings while increasing the availability of dietary energy and reducing the effective variation in energy content."
So personally, I would be cautious.
Feeding ducks with Barley is fine though, I have read about it being a suitable replacement for wheat as far as waterfowl are concerned.
Hope this helps,
Tim