Influence of leafy spurge on forage utilization by cattle.

A 3-year field study was conducted near Grassrange, Montana. (Latitude 46 degrees 50'N and Longitude 108 degrees 50'W) to determine the effect of leafy spurge (Euphorbia esula L.) shoot density, control, and canopy cover on the utilization of forage by cattle. Picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) was applied at 0.28 to 2.24 kg ae/ha on leafy spurge-infested native pasture to establish different levels of leafy spurge shoot density and canopy cover. Utilization of forage was influenced by leafy spurge shoot density (r = -0.65) and canopy cover (r = 0.87) and was not related to the amount of forage (r = -0.1) produced. A leafy spurge canopy cover of 10% or more and a leafy spurge shoot control value of 90% or less resulted in a significant decrease in utilization of forage by cattle.