Do hungry sheep graze more death camas (Zigadenus paniculatus) than satiated animals

Authors: Stonecipher, Clinton; Welch, Kevin; Lee, Stephen; PALMER, MATT - Utah State University; Cook, Daniel

Submitted to: Applied Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: Death camas begins growth prior to grasses and other forages and a lack of alternative forages during this season can result in livestock consuming death camas and becoming poisoned. Similarly, placing hungry animals in death camas rangelands can result in livestock poisoning at any stage of the growing season. The objectives of this study were to 1) graze hungry, partially satiated, and satiated sheep on rangelands containing death camas to determine if hungry sheep consume more death camas, and 2) to graze sheep at early vegetative and flowering stages of plant phenological development to determine if more sheep are poisoned at the early vegetative stage when death camas is more toxic. Sheep grazed at three locations over four separate years. Death camas alkaloid concentrations were greater at the vegetative than the flowering stage of plant growth. Bite count data and fecal DNA metabarcoding did not confirm our hypothesis that hungry sheep consume more death camas than satiated sheep. However, we did observe sheep in the Hungry and Partially Satiated treatment become ill after grazing death camas. In conclusion, hungry sheep displayed signs of intoxication but were able to limit activity and recover from poisoning. Caution should be taken anytime that sheep are grazing in an area consisting of death camas plants.

Technical Abstract: Death camas plants (Zigadenus spp.) begin growth prior to grasses and other forages, and a lack of alternative forages during this season can result in livestock consuming death camas. Similarly, placing hungry animals in death camas rangelands can result in livestock poisoning at any stage of the growing season. The objectives of this study were to 1) graze hungry (HU), partially satiated (PS) and satiated (SA) sheep on rangelands containing death camas to determine if hungry sheep consume more death camas, and 2) graze sheep at early vegetative and flowering stages of plant phenological development to determine if phenological stage influences relative palatability. Sheep grazed at three locations over four separate years. Differences in bite counts between forage classes within treatment groups at the different grazing periods (P < 0.0001) were observed across all four years of grazing. Death camas alkaloid concentrations varied over the different years of the grazing study (P =0.0009) and alkaloid concentrations were greater at the vegetative than the flowering stage (P < 0.0001). Bite count data and fecal DNA metabarcoding did not confirm our hypothesis that hungry sheep consume more death camas than satiated sheep. However, we did observe sheep in the HU and PS treatment become ill after grazing death camas. In conclusion, hungry sheep displayed signs of intoxication but were able to limit activity and recover from poisoning. Caution should be taken anytime that sheep are grazing in an area consisting of death camas plants.