Date of Graduation

8-2012

Document Type

Thesis

Degree Name

Master of Science in Animal Science (MS)

Degree Level

Graduate

Department

Animal Science

Advisor

Dirk Philipp

Committee Member

Kenneth Coffey

Second Committee Member

Mary Savin

Keywords

Biological sciences; Cattle; Legumes; Nitrogen

Abstract

Interest in substituting legumes for N fertilizer in beef cattle grazing systems has recently increased with rising fertilizer prices. Legumes are well known for their ability to fix atmospheric N and decrease dependence on input of N fertilizer. However, there are still difficulties associated with legume utilization including establishment and persistence. Two experiments were conducted to evaluate legume performance under herbivory. The objective of Experiment 1 was to compare forage production and beef cattle gains from annual ryegrass [Lolium multiflorum (L.)] and bermudagrass [Cynodon dactylon (L.) Pers.] pastures fertilized with N or overseeded with legumes. Gelbvieh × Angus crossbred heifers (n = 40; average of 264 ± 45.62 kg initial BW) were assigned to one of eight, 2-ha pastures in the spring of each of the three years of the study. All pastures were overseeded with `Marshall' annual ryegrass, and were not seeded with any clover (Con) or overseeded with `Dixie' crimson clover [(C; Trifolium incarnatum (L.)], `Osceola' white clover [L; Trifolium repens (L.)], or a combination of crimson clover and white clover (CL). Grazing initiated early- to mid-spring and continued until early- to mid-May. Total body weight (BW) gain was greater (P < 0.05) in the spring season for Con compared to the legume treatments. However, average daily gain (ADG) was not different (P > 0.05) in spring, and there were no differences (P > 0.05) in total BW gain or ADG in summer. Although clovers may not be able to entirely eliminate the need for N fertilizer, they may help reduce dependency on it by aiding in the production of cattle having similar BW gains to cattle grazing traditionally fertilized pastures. The objective of Experiment 2 was to monitor the persistence of three annual and three perennial legume species overseeded into common bermudagrass pastures that were rotationally stocked. The three annual species were crimson clover (cv. Dixie), arrowleaf clover [Trifolium vesiculosum (Savi), cv. Yucchi], and hairy vetch [Vicia villosa (Roth), cv. VNS]. The three perennial species were white clover (cv. Durana), red clover [Trifolium pretense (L.), cv. Cinnamon Plus], and alfalfa [Medicago sativa (L.), cv. Ameristand 403T]. Annual clovers were managed to reseed themselves. Crimson clover persisted two years and all other annul species for three years. Among perennial legumes, only white and red clovers persisted for three years, while alfalfa stands disappeared after the second year of the study. The frequency of occurrence of weeds and other undesirable plants generally increased each year while legume populations declined in all six clover treatments. In order to maintain healthy and dense legume populations in grazing systems, it may be necessary to develop and adopt aggressive weed control strategies using chemical compounds including improved grazing management strategies.

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