Date of Award:

2005

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Ecology

Department name when degree awarded

Range Science

Advisor/Chair:

John C. Malechek

Abstract

Several experimental lines of forage kochia [Kochia prostrata (L. Shrad.)] have potential to provide taller forage on fall and winter rangelands than the only released variety of forage kochia, Immigrant. This study was conducted to determine differences in cattle utilization among experimental lines of forage kochia and relate them to forage quality and morphological attributes. The utilization of forage kochia was also compared to 'Ladak ' alfalfa [Medicago saliva (L.)] and two entries of winterfat [Krashnennikovia species (Guldenstaedt)]. Cattle utilization was determined by calculating a biomass consumed value and a percent biomass consumed value. Dry weights for each plant were taken after grazing and subtracted from a pre-grazing dry weight (predicted using a quadratic regression equation) that produced the biomass consumed value. The percent consumed value was calculated by dividing biomass consumed by pre-grazing dry weight. Ocularly estimated utilization scores (OU) were also used to measure utilization. Forage quality traits were analyzed on each entry using near infrared reflectance spectroscopy. Morphologic and phenological characteristics potentially related to utilization were made by physical measurements and visual evaluations. There were significant differences among forage kochia accessions for all traits evaluated. Four entries, including Immigrant and Ladak alfalfa, were significantly higher in percent herbage consumed than the other entries . These same entries were consistently high in OU ratings , forage quality analyses , and most morphological characteristics. Pre-grazing dry weight (r = -0.96 , P < 0.0001) , stem length (r = 0.67, P < 0.0001), and branch density (r = 0.63, P < 0.0001) were all highly correlated with utilization. Crude protein (partial R2 = 0.253 , P ≤ 0.0001) was the only forage quality trait associated with utilization using a stepwise regression to predict utilization. From this study we conclude that some forage kochia accessions are very palatable. They are comparable to Ladak alfalfa, and utilized more than Krashnikova spp., a desirable forage on western rangelands.

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