I have two 55 gallon free choice protein feeders. Deer were emptying them biweekly and everything was great. Now that acorns are getting all the attention and they aren't eating much protein mold has developed on the top layer of protein in the barrel. Anyone experienced this? Bad seal on the barrel lid? Common? Thanks.

All protein has moisture in it when it is made. So a tightly sealed barrel will sweat or get condensation (with hot sun and then cooling down at night) on the bottom of the lid from moisture collecting there then it rains down on the pellets. Vent the feeder or use a slightly larger lid that is loose fitting with a gap between the lid and top of barrel. That way the moisture can escape.

Thanks!

Same thing can happen to a corn feeder. You really don't want an air tight seal up top.