Influence of grazing pressure on cattle consumption of the teratogenic plant velvet lupine

Authors: Ralphs, Michael; Pfister, James; Panter, Kip; Lee, Stephen; MOTTERAM, ERNIE

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2010
Publication Date: 3/1/2011
Citation: Ralphs, M.H., Pfister, J.A., Panter, K.E., Lee, S.T., Motteram, E.S. 2011. Influence of grazing pressure on cattle consumption of the teratogenic plant velvet lupine. Professional Animal Scientist. 27(2):101-8.

Interpretive Summary: Intensive rotation grazing systems may force cattle to graze lupine in early summer when they are in the critical period of gestation (40-100 days), thus causing crook calf disease. Three intensive grazing trials evaluated cattle consumption of lupine in its stages of phenological development through the growing season, in relation to increasing grazing pressure. In May, cattle preferred green cheatgrass and immature forbs and did not graze lupine until all other forage was depleted. In June, cheatgrass was dry and cattle preferred forbs that were flowering. As availability of palatable forbs declined, cows started eating lupine and continued through this trial. In July when forbs were mature and rank, cattle ate lupine at the beginning of the trial, and reverted to dry cheatgrass as lupine became limited. We conclude that lupine is not palatable early in the growing season in May and early June, but cattle can be forced to graze it as availability of green cheatgrass and other forbs declines. Intensive grazing systems that force cattle to utilize all forage may enhance the risk of crooked calf disease by forcing cattle to graze lupine throughout the grazing season.

Technical Abstract: Lupine species may contain teratogenic alkaloids that cause birth defects called crooked calf syndrome. If pregnant cows ingest toxic lupine between days 40 and 100 of gestation, fetal movement is impaired and irreversible skeletal defects occur. There is a need to determine the time and conditions cattle graze velvet lupine (Lupinus leucophyllus Dougl. Ex. Lindl.) to prevent ingestion of this toxic forb during the critical period of gestation. Intensive grazing trials evaluated cattle consumption of lupine in its stages of phenological development through the growing season, in relation to increasing grazing pressure. Ten Hereford cows and a bull grazed velvet lupine-infested rangeland in three seasonal grazing pressure trials in eastern Washington. Pastures were fenced to limit forage availability to the amount required for 6 day trials in 2007 and 10 day trials in 2008. Diets were estimated by bite count. In May, cattle preferred green cheatgrass (Bromus tectorum L.) and immature forbs and did not graze lupine until all other forage was depleted. In June, cheatgrass was dry and cattle preferred forbs that were flowering. As availability of palatable forbs declined, cows started eating lupine and continued through this trial. In July when forbs were mature and rank, cattle ate lupine at the beginning of the trial, and reverted to dry cheatgrass as lupine became limited. We conclude that lupine is not palatable early in the growing season in May and early June, but cattle can be forced to graze it as availability of green cheatgrass and other forbs declines. Intensive grazing systems that force cattle to utilize all forage may enhance the risk of crooked calf disease by forcing cattle to graze lupine throughout the grazing season.