Sheep preference for leafy spurge from Idaho and North Dakota

Three trials were conducted to determine if low ingestion of some leafy spurge (Euphorbia esula L.) by sheep is primarily due to differences in sheep or in leafy spurge. In the first trial, pastures in Idaho and North Dakota were grazed by sheep originating from both states. Generally, sheep from both states grazed the leafy spurge growing in the Idaho pastures reluctantly but grazed the leafy spurge growing in the North Dakota pastures in proportion to its availability (P = 0.003). In the second trial, ingestion of air-dried leafy spurge by penned sheep was compared by offering samples from the 2 locations simultaneously. Sheep consumed more (P = 0.0001) leafy spurge from North Dakota than from Idaho. In the third trial, penned sheep were simultaneously offered Idaho leafy spurge harvested from fertilized and non-fertilized sites. Initially, equal amounts of fertilized and unfertilized leafy spurge were consumed (P ≥ .68), but by the fourth day sheep had an obvious preference for leafy spurge from the fertilized site (P = 0.01). These trials indicate that preference for leafy spurge by sheep differs depending on site, and that using sheep to manage leafy spurge may be more successful on soils with relatively high fertility.