The long awns irritate and cause abscesses in the mouths and nostrils of grazing animals.
Livestock generally avoid purple threeawn for most of the year when other forage is available.
Purple threeawn is generally unpalatable due to its spike-like awns, which can injure grazing animals. Bison on blue grama-buffalograss prairie in northeastern Colorado commonly grazed Fendler threeawn in March and August. Purple threeawn tends to increase with grazing.