Date of Award:

12-2008

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Committee Chair(s)

Frederick D. Provenza

Committee

Frederick D. Provenza

Committee

Juan J. Villalba

Committee

Carl D. Cheney

Abstract

All plants contain primary and secondary compounds. Primary compounds are needed by plants and herbivores for maintenance, growth, and reproduction, while secondary compounds play roles as diverse as protecting plants from ultraviolet radiation, defenses against herbivores, pollination attraction, and stress resistance. Secondary compounds have nutritional and medicinal benefits for herbivores as well, especially when eaten in diverse combinations that complement one another. While complementarities among secondary compounds are an important but little understood area of plant-herbivore interactions, even less is known about how the sequences of eating plants with different compounds affects foraging behavior, though they may be critical. In three trials, I determined if the sequence in which lambs ate endophyte-infected tall fescue (alkaloids), birdsfoot trefoil (tannins), and alfalfa (saponins) affected their foraging behavior.

When lambs grazed on monocultures they spent similar amounts of time grazing regardless of which forage they grazed. Lambs that grazed in a sequence of different forages tended to subsequently eat less alfalfa pellets in pens than lambs that grazed a monoculture, which suggests they better met their nutritional needs on mixtures than on monocultures. Likewise, lambs that grazed a monoculture of alfalfa or fescue spent more time grazing during the first 45 min than in the subsequent 45 min, while lambs that grazed alfalfa during the first 45 min and then fescue spent more time grazing in the subsequent 45 min, suggesting lambs satiate faster when they have fewer choices.

While the foraging sequences I examined generally allowed animals to consume more than they would if they grazed in monocultures, there is still a need to further explore how different plants and foraging sequences influence the level of consumption by livestock of forages on pastures that contain various secondary compounds.

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