To supplement a pasture when the season depletes food sources a compost pile is nice. Its full of bugs in winter and retains moisture (or you need to add some for proper composting) so it is ready to provide natural feed when the pasture depletes.
I just use 20% but I had posted that I thought the 28% might be better. But I was going under the ignorant assumption that higher is always better. Not saying its wrong but since I never used it to compare results it is ignorant of me to say it. 20% meat bird feed was made for feeding birds...