After doing more reading from the net...and searches here, this is beginning to look like dallisgrass. And it seems it's desirable.
I don't think my cows are doing much with it. they may be eating it, but if so, they have a lot of other things they eat before that. It grows in clumps, and as such, tends to make the pasture look trashy....but if it's a desirable grass, perhaps under drought etc conditions...then I'll just leave it alone.
Definitely not dallisgrass -- smutgrass is closer to the mark. Velpar used to be recommended for killing smutgrass, probably still is --- but a strong concentration of Roundup might do the trick as well. If using Velpar you have to be real careful about using it near trees, or where moving water can carry it to trees (it will kill them). Also, if it were dallisgrass your cows would be gobbling it up almost with as much gusto as if it were Johnson grass. Both smutgrass and dallisgrass often have a moldy, blackish looking seed head, but they are entirely different in shape and appearance. When you see the single long stems with about 3 or 4 inches of blackish looking seed head (not multiple heads at the end of the stem) you have smutgrass.
Smutgrass is what it looks like to me too. Latin name is Sporobolus indicus. Also known as Indian Rush or indian dropseed. Its a royal pain in the but. What type grass is in your pasture and I might be able to help you with something off the label.