Date of Award:

5-2025

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Jennifer Wilson McAdam

Committee

Jennifer Wilson McAdam

Committee

Juan V. Villalba

Committee

Stephan Van Vliet

Abstract

Grass-dominated rangelands in the Western United States often lack sufficient protein for pregnant cows after grasses mature in mid- summer, leading ranchers to rely on expensive feed supplements such as protein cubes or alfalfa hay. The goal of this study was to screen 27 perennial legume and forb species with the potential to remain green into late summer and provide sufficient protein to supplement cows on grass-dominated rangeland. Three experiments were carried out to understand germination of species, plant establishment and persistence at five Utah locations, and agronomic characteristics. The seed of five hard-to-germinate species were studied for the ability of extended cold treatment to improve germination. The germination of Lewis flax and Utah sweetvetch was improved by stratification. Arrowleaf balsamroot and fernleaf biscuitroot required stratification for germination, but germination percentage remained lower than the seed tag-based expectation. At five field sites across Utah, sainfoin, small burnet, and 'Ladak' alfalfa consistently became established in dense plant stands. Other species established moderate stands while many failed to establish at all. Ladak alfalfa, birdsfoot trefoil, small burnet, and sainfoin were studied for nutritive value characteristics from June to October of 2023 and 2024. In 2024, crested wheatgrass, falcata alfalfa, showy goldeneye, and Utah sweetvetch were also evaluated for nutritive value and dry matter yield. Additionally, Ladak alfalfa and sainfoin were evaluated for leaf-to-stem ratio over the season. Only Ladak alfalfa (2023) and Utah sweetvetch (2024) maintained protein levels above the minimum cattle requirement (7.5%) through October. Birdsfoot trefoil and sainfoin, contained condensed tannins and small burnet contained hydrolysable tannins. Showy goldeneye, and Utah sweetvetch contained both tannins. Further, all four species tested in 2023 accumulated a unique range of secondary metabolites. Ladak alfalfa contained a higher leaf-to-stem ratio than sainfoin from June to August. Crested wheatgrass, Ladak alfalfa, falcata alfalfa, and sainfoin maintained higher dry matter yield through October, demonstrating their ability to extend forage availability on rangeland. Secondary metabolites such as tannins can shift nitrogen excretion from urine to feces, reduce methane emissions, and lower parasitic burdens in cattle while other flavonoids richness can provide antioxidant and anti-inflammatory properties to ruminants.

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