Don't!! sprout sorghum (milo--the brown-ish/red bigger round seeds in wild bird seeds and scratch) and let it grow leaves hardly at all. The young plants develop a poison... hydrocyanic, or prussic acid fairly early on in the green leaves. That's about the same stuff in the leaves of the common wild cherry trees. You can stick the leaves in a big bunch and make silage (let it ferment) after 2-3 weeks like the farmers do and feed it though....not so desirable after fermenting in the smell department..
If the millet in the mix is a true millet, it can be used for green forage cuz it has very low levels if any of the prussic acid content.
The sorghum/milo warning is not an old wives tale. Every cattleman/milker/feedlot that grows their own feed or makes silage from milo knows this and every Agriculture College in the world posts warnings about it.
Sorghum seed sprouts with short white roots are good........but NO GREEN leaves showing!
This is the wild bird seed...is that milo/sorghum seeds?