The plants animals include in their diets are important to their health and productivity. The order in which plants are eaten may also play an important role in the intake of plants high in secondary metabolites.

Former USU graduate student, Travis Mote, found that sheep ate more foods that contained terpenes, like those found in sagebrush or juniper, after eating foods high in tannins, plants like oak brush, bitterbrush, and sericea. In addition, Mote found lambs that learned to eat terpenes after eating tannins had a higher preference for terpenes than lambs that did not eat foods high in tannins before terpenes. It’s thought that tannins bind to terpenes in the gut.

USU graduate student, Emily Lockard, is following-up on Mote’s work. Her studies will investigate how the order in which sheep eat pasture plants that differ in plant secondary compounds affect diet selection and time spent foraging by sheep. She plans to determine if foraging time on various plant species increases when sheep are rotated in different sequences on pastures containing high-alkaloid varieties of reed canarygrass or tall fescue, high-tannin varieties of birdsfoot trefoil, and high-saponin varieties of alfalfa. The results of this study will increase understanding of the role of forage sequences in the ability of animals to increase their intake of plants containing secondary compounds.

Mote and Lockard’s findings may also shed new light on a paper recently published in the Journal of Ecology and Range Management. Researchers found sheep with strong preferences for sagebrush (terpenes) also ate a lot of bitterbrush (tannin). Were these just shrub-loving sheep as researchers speculated or did sheep learn to mix shrubs, one high in tannin and another in terpenes, to their benefit?

The research will be conducted at Utah State University. Fred Provenza, Professor, and Juan Villalba, Research Assistant Professor, both of the Department of Wildland Resources will oversee the project.