I was talking about sour crop, not impacted crop. The crops were not blocked at all by anything-I know this because they were opened up and examined. They simply quit functioning. Impacted crop is not at all the same; we've seen that once or twice.
We've been around the block a few times with crop issues, three of my four Blue Orp hens died from them. That breed variety tends toward pendulous crop and that is exacerbated by the depleted bodies caused by their molts. All crop issues occurred during hard molt--some could process small amounts of moldy feed, but any hens who were not 100% top capacity were the ones whose crops quit. The feed was in there in a mushed up ball, not hay/grass/fibrous material, just a ball of mushed up layer pellets (we use the mini-pellets), softened by water they drank, that refused to move back through the proventriculus. You are assuming they were impacted by fibrous material or blocked up and they were not, not one of them. No blockage-we made sure of that.
Sour crop is basically a fungal infection, which is why acidified copper sulfate in water is one way to treat it.
Your first link is making impacted crop and sour crop the same condition and they are two separate things. Impacted crop may require surgery, which we've also done. Sometimes, even when the crop is evacuated and all seems fine, it still refuses to be "jump-started".
All those suggestions to make the hens upchuck, though, can backfire badly. They can aspirate and choke in your arms. Trust me, I know- that one started throwing up on her own as I was taking her toward the house to start treatment and we encouraged her to continue and she died right there. Best to stop feeding for 24 hours, put ACV or copper sulfate in the water and allow only that. Then, add plain no sugar yogurt the next day, all the while massaging the crop (not to make the bird regurgitate, though) several times a day. We've fixed some and lost some to it so we are very, very familiar with the causes and cures.
Back to the original intent of the thread, I wouldn't sweat it, but yes, moldy feed can be detrimental to chickens so just check for places where it may be sitting out and has started to ferment, like under leaves or rocks, etc.
As long as you're posting links, how about one from the university rather than a blog?
from this article on feeding chickens:
http://www.poultry.msstate.edu/extension/pdf/is1214.pdf
Keep water and feed troughs clean of
droppings, litter, soil, and other contaminants.
Keep feed troughs clean and dry. Empty feed
troughs at least two or three times weekly (daily if
necessary) and refill with dry, fresh feed. Do not
wash feed troughs unless they are contaminated
with harmful residues or unless the feed gets wet.
Do not let the feed become moldy. Moldy feed can
kill chickens.
