Setaria parviflora - Knotroot (or Perennial) Foxtail (or Bristlegrass), a problem in pastures and hay fields.
The spikes, when dried out, cause ulceration in the mouth of horses. At any stage of its life this plant is of marginal value as feed for livestock. Even spot application of glyphosphate (Roundup) will not surely kill it. Provided that you don't have a severe infestation the most certain way to rid your land of this species is to dig each plant out being sure to remove all of the rhizomes from the soil. Here on the southern plains of the U.S. this weed seems to thrive best following an exceptionally wet spring.
It's a shame that something as attractive as this will halve the value if it is present in hay that you sell.
D850 CV 125 1/20 f11 ISO 400