|Knight, Anthony - COLORADO STATE UNIVERSITY|
|Waggoner, James - UNIVERISTY OF WYOMING|
|Hall, Jeffery - UTAH STATE UNIVERSITY|
Submitted to: Journal of Range Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 24, 2001
Publication Date: July 1, 2002
Citation: PFISTER, J.A., GARDNER, D.R., STEGELMEIER, B.L., KNIGHT, A.P., WAGGONER, J.W., HALL, J.O. PLAINS LARKSPUR (DELPHINIUM GEYERI) GRAZING BY CATTLE IN WYOMING. JOURNAL OF RANGE MANAGEMENT. 2002. Interpretive Summary: Plains larkspur (Delphinium geyeri) is a major cause of cattle poisoning in the northern Great Plains of Wyoming and Colorado. The perennial larkspur typically begins growth in spring before grasses have begun growth, and thus may offer green forage while grasses are dormant. Plains larkspur contains numerous diterpenoid alkaloids. No grazing studies have examined cattle consumption of plains larkspur. The objective of this study was to evaluate the amount and timing of larkspur consumption by cattle in relation to its phenology, toxicity, and other potentially important variables such as weather. This study suggests that it will be difficult to predict plains larkspur consumption based on larkspur growth patterns or weather. As with tall larkspurs, cattle sometimes increased plains larkspur consumption when temperatures were cooler than normal. Nonetheless, this pattern was not consistent and therefore will not serve as a basis for management recommendations. Currently, our best management recommendation is to ensure that other desirable forage production is ample when cattle graze in plains larkspur-infested pastures. Extra caution may be warranted if cattle are in low body condition.
Technical Abstract: Plains larkspur (Delphinium geyeri) is a major cause of cattle deaths in the northern Great Plains. We examined larkspur ingestion by grazing cattle in relation to larkspur phenology and weather conditions. Four summer grazing trials were conducted near Cheyenne (1996 and 1997) and Laramie, Wyoming (1998 and 1999). During both 1996 and 1997, cattle ate 0.5 to 1% of bites as larkspur during May, then consumption decreased to nearly zero during the remainder of both summers. When eaten, larkspur was typically consumed during cool, foggy weather conditions. Cattle ate substantial amounts of plains larkspur (herd average 3%) during the vegetative and bud stages from mid-May into early June, 1998. Cattle may have eaten more larkspur because drought reduced spring availability of green grass. Cattle particularly ate larkspur during times of cooler ambient temperatures during 1998. During 1999 cattle ate essentially no plains larkspur during the vegetative and bud stages, but ate larkspur (herd average 5%) during the flower and pod stages when larkspur plants were beginning to desiccate and ambient temperatures were above average. This series of trials indicates that it is difficult to predict plains larkspur consumption based on larkspur growth patterns or weather. Although cattle sometimes increase plains larkspur consumption when temperatures are cooler than normal, this pattern is not consistent enough to serve as a basis for management recommendations.