Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 52-64). Also available on the World Wide Web.

A study investigating the effect of sheep stocking density and grazing duration on forage intake, grazing efficiency, dietary selectivity and subsequent forage accumulation in tall fescue(Festuca arundinacea)- subclover(Trifolium subtaranium) pastures was conducted near Corvallis, Oregon during early and late spring in 1988 and 1989. Grazing treatments were 2, 6, and 10-day duration and corresponding stocking densities 380, 130, 78 and 1390, 460 and 280 ewes/ha during early and late trials each year, respectively. Average daily intake and grazing efficiency were highest (P< 0.05) in the 10-day duration and lowest in the 2-day duration. During the first 2 days of all duration treatments, average daily intake decreased as stocking density increased (P< 0.05). Manure cover and crowding stress may explain lower average daily intake under the shorter duration/high density treatments. However, stocking density had little effect on grazing efficiency. This was largely due to the high amount of forage destroyed under the low density treatments which offset the effect of higher forage intake of that treatment. Within the 10-day duration treatment, average daily intake was the same over time (P> 0.05), while grazing efficiency decreased as grazing progressed (P< 0.05). The low grazing efficiency during the early stages of grazing reflected high initial forage destruction probably caused by the movement of animals at the start of grazing to establish bedding and habitual use areas. Growth rate of forage after grazing was highest in the longer duration paddocks and lowest in the shorter duration paddocks (P< 0.05), but the yield was similar under all treatments (P> 0.05). Although short duration/high density grazing is considered to be non-selective, sheep were equally or more selective under very short duration/very high density compared to longer duration/lower density treatments in this study. The 2 days duration was not an attractive management option since the intake and grazing efficiency were low, and the animals were selective. / Graduation date: 1993

Tall fescue is the most common cool-season grass in the eastern USA, with broad economic and ecological importance to the region. Tall fescue is known to associate with a fungal endophyte, Neotyphodium coenophialum, whose presence can decrease biotic and abiotic stress experienced by the plant. This thesis evaluates the response of tall fescue and the fungal endophyte symbiosis to predicted climate change. I participated in two multi-factor climate change projects where I investigated the response of tall fescue tissue chemistry and growth to various climate change factors. Endophyte-infected (E+) tall fescue had decreased alkaloid production under elevated CO2 but increased alkaloid production under elevated temperatures. Significant differences between E+ and E- (endophyte-free) tall fescue tissue chemistry were also found, suggesting the endophyte interacts with the plant response to abiotic stress. Although several studies have reported benefits of endophyte infection for tall fescue growing under drought stress, my research found no differences between E+ and E- total growth and surprisingly showed increased mortality of E+ individuals under elevated temperature. Taken together, my research indicates that this grass-fungal relationship will respond to climate change, and may produce dramatic and unforeseen results that question the widely believed mutualistic nature of the symbiosis.

Three experiments were conducted to explore the effect of fescue toxicosis on vasoconstriction and various parameters of the estrous cycle. In the experiment of Chapter 3, a 2x2 crossover experimental design with repeated measures was implemented to test whether the ingestion of endophyte-infected tall fescue seed would alter blood hormone concentrations of prolactin, progesterone, and estradiol, interovulatory intervals, and corpus luteum blood flow. Also, Doppler ultrasonography was used to assess whether palmar artery and palmar vein lumen diameter, area, circumference, and resistivity index could be altered by the ingestion of endophyte-infected tall fescue seed. Ingestion of endophyte-infected tall fescue seed significantly decreased palmar artery resistivity index, area, and circumference, and palmar artery and palmar vein lumen diameter, but did not alter interovulatory intervals, serum concentrations of prolactin, progesterone, estradiol, or corpus luteum blood flow. Experiments 1 and 2 from Chapter 4 profiled the dopaminergic, serotonergic, and α-adrenergic receptor types and subtypes, as expressed within the equine medial palmar artery, medial palmar vein, and uterine artery transcriptomes. Combined results from Chapters 3 & 4 imply that relative quantity of serotonergic receptor subtypes within a vessel may be related to with the severity of that vessel's vasoconstrictive response to endophyte-infected tall fescue.

Understanding the nutrient dynamics of pastures is essential to their profitable and sustainable management.  Tall fescue [Schendonorus phoenix (Scop.) Holub.] is the predominant forage species in Virginia pasturelands.  Although tall fescue pasture is common, little research has attempted to document how soil and herbage nutrient concentrations change through time.  This thesis summarizes two studies conducted within the context of a larger grazing systems project near Steele's Tavern, VA.  The objectives were to: (1) examine temporal changes in plant available soil nutrient concentrations in four grazing systems, (2) determine how hay feeding and use of improved forages affected soil and herbage nutrient concentrations (3) examine the relationship between and variability within soil and herbage nutrient concentrations, (4) analyze the seasonal variation in herbage mineral concentration with regard to beef cattle requirements, and (5) create a statistical model to predict variation in herbage mineral concentration across the growing season.  Analysis of plant and soil nutrients through 5 years of grazing produced several important findings.  Soil pH, P, and Ca, Mg, and B declined through five years of grazing.  Higher concentrations of herbage N and K and soil P, K, Fe, Zn, and Cu were measured in hay feeding paddocks.  Herbage nutrient concentrations showed less variability in P and K than did soil test results.  Fertility testing in pastures is important to monitor changing nutrient concentrations, and this study showed that herbage analysis may provide a more stable and accurate assessment of pasture fertility than soil testing.  Pasture herbage, grown without fertilization, contained sufficient concentrations of macronutrients to meet the requirements of dry beef cows through the growing season and to meet the requirements of lactating beef cows in April.  A model was developed using soil moisture and relative humidity that predicted (R2 = 0.75) variation in herbage mineral concentration throughout the growing season.  As described in this thesis, use of modeling to predict nutrient dynamics in pasture could allow for more efficient mineral supplementation strategies that lead to improved profitability, nutrient retention, and livestock health. / Master of Science

Thesis (M. Agr. Sc.) -- Lincoln University, 2008. / Also available via the World Wide Web.

Thesis (M.S.)--University of Tennessee, Knoxville, 2004. / Title from title page screen (viewed Oct. 04, 2004). Thesis advisor: F. Neal Schrick. Document formatted into pages (xiii,105 p. : ill.). Vita. Includes bibliographical references (p. 86-104).

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 11, 2010). Thesis advisor: Dr. Robert L. Kallenbach. Vita. Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains x, 149 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 130-149).

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 73-86). Also available on the World Wide Web.