Influence of burning and grazing management practices on subirrigated Sandhill meadow hay production

Subirrigated meadows are a valuable forage resource to Sandhills ranching operations being used for hay production, grazing, or a combination of both. Practices that sustain meadow productivity should be encouraged to ensure a consistent feed supply for cattle. The potential influence of prescribed burning or pre-freeze and post-freeze grazing on forage production and quality are not well understood on these meadows. In grasslands, including meadows, excess dead plant material can accumulate, causing a potential reduction in forage yield and quality. Results of our three-year field study suggest that burning meadows in the spring is a suitable management option to remove dead plant material without negatively affecting future hay production. Additionally, when burning was followed by either grazing exclusion or grazing from early-May to early-June, grazing had a greater influence on end of season biomass, with no interacting effect of burning and grazing. Quality of warm-season grasses was increased slightly following burning, but most improvements in quality were minimal and were a result of spring grazing. Study two evaluates a common practice of grazing meadows in the fall (pre-freeze) and winter (post-freeze) months. In our study, grazing in the fall when vegetation was still green was detrimental to future graminoid production. Relative to pre-freeze grazing, postponing grazing until plant dormancy (post-freeze) returned higher yields of graminoids and total live plant biomass. Deterring meadows from grazing in the fall and winter (control) produced graminoid and total live biomass that was similar to post-freeze treatments. Relative to pre-freeze treatments, summer biomass of ungrazed controls were generally higher in graminoid biomass, while similar in total live biomass. Quality of subsequent year’s forage in pre-freeze treatments was significantly higher than the control or post-freeze treatments and met the total digestible nutrient requirement of lactating cows. Our studies show that tradeoffs in quantity and quality are common under any practice. Therefore individual management objectives should be considered when deciding if a practice is right for them. Advisors: Mitchell Stephenson and Jerry Volesk

Spring Meadow Management Practices: What’s a Rancher to do?

• Subirrigated meadows are a valuable forage resource to ranching operations in the Nebraska Sandhills, being used for both hay production and livestock grazing. • The water table of these meadows is within one meter of the soil surface during the growing season. • In some years, wet conditions hinder meadow utilization, resulting in a buildup of standing dead and litter plant material which can lower forage production. • Investigate if burning and mowing are effective strategies to remove dead plant material from meadows • Determine if burning or mowing interact with grazing to influence end of season forage production Burning or mowing effectively removes dead plant material from meadows with no later loss in forage production. Burning and mowing do not interact with grazing to influence later forage production. Spring grazing acted independently to significantly lower end of season forage production. Conclusions • Ranchers can use burning or mowing to effectively remove dead plant material from subirrigated meadows in the Nebraska Sandhills with no later losses in forage production (Fig.1 & Fig.2). • On the other hand, spring grazing reduces end of season forage production (Fig.3). Therefore, caution should be used with spring grazing if a rancher’s goal is to maximize hay yields from meadow forage

Influence of burning and grazing management practices on subirrigated Sandhill meadow hay production

Subirrigated meadows are a valuable forage resource to Sandhills ranching operations being used for hay production, grazing, or a combination of both. Practices that sustain meadow productivity should be encouraged to ensure a consistent feed supply for cattle. The potential influence of prescribed burning or pre-freeze and post-freeze grazing on forage production and quality are not well understood on these meadows. In grasslands, including meadows, excess dead plant material can accumulate, causing a potential reduction in forage yield and quality. Results of our three-year field study suggest that burning meadows in the spring is a suitable management option to remove dead plant material without negatively affecting future hay production. Additionally, when burning was followed by either grazing exclusion or grazing from early-May to early-June, grazing had a greater influence on end of season biomass, with no interacting effect of burning and grazing. Quality of warm-season grasses was increased slightly following burning, but most improvements in quality were minimal and were a result of spring grazing. Study two evaluates a common practice of grazing meadows in the fall (pre-freeze) and winter (post-freeze) months. In our study, grazing in the fall when vegetation was still green was detrimental to future graminoid production. Relative to pre-freeze grazing, postponing grazing until plant dormancy (post-freeze) returned higher yields of graminoids and total live plant biomass. Deterring meadows from grazing in the fall and winter (control) produced graminoid and total live biomass that was similar to post-freeze treatments. Relative to pre-freeze treatments, summer biomass of ungrazed controls were generally higher in graminoid biomass, while similar in total live biomass. Quality of subsequent year’s forage in pre-freeze treatments was significantly higher than the control or post-freeze treatments and met the total digestible nutrient requirement of lactating cows. Our studies show that tradeoffs in quantity and quality are common under any practice. Therefore individual management objectives should be considered when deciding if a practice is right for them. Advisors: Mitchell Stephenson and Jerry Volesk

Functional and Neuroanatomic Specificity of Episodic Memory Dysfunction in Schizophrenia: A Functional Magnetic Resonance Imaging Study of the Relational and Item-Specific Encoding Task

ImportanceIndividuals with schizophrenia can encode item-specific information to support familiarity-based recognition but are disproportionately impaired encoding interitem relationships (relational encoding) and recollecting information. The Relational and Item-Specific Encoding (RiSE) paradigm has been used to disentangle these encoding and retrieval processes, which may depend on specific medial temporal lobe (MTL) and prefrontal cortex (PFC) subregions. Functional magnetic resonance (fMRI) imaging during RiSE task performance could help to specify dysfunctional neural circuits in schizophrenia that can be targeted for interventions to improve memory and functioning in the illness.ObjectivesTo use fMRI to test the hypothesis that schizophrenia disproportionately affects MTL and PFC subregions during relational encoding and retrieval relative to item-specific memory processes, and to use fMRI results from healthy individuals serving as controls to establish neural construct validity for RiSE.Design, setting, and participantsThis multisite, case-control, cross-sectional fMRI study was conducted between November 1, 2010, and May 30, 2012, at 5 Cognitive Neuroscience Test Reliability and Clinical Applications for Schizophrenia sites. The final sample included 52 outpatients with clinically stable schizophrenia and 57 demographically matched healthy control participants. Data analysis was performed between February 1, 2013, and May 30, 2014.Main outcomes and measuresBehavioral performance speed and accuracy (d') on item recognition and associative recognition tasks. Voxelwise statistical parametric maps for a priori MTL and PFC regions of interest to test activation differences between relational and item-specific memory during encoding and retrieval.ResultsItem recognition was disproportionately impaired in patients with schizophrenia relative to healthy control participants following relational encoding (F1,107 = 4.7; P = .03). The differential deficit was accompanied by reduced dorsolateral PFC activation during relational encoding in patients with schizophrenia compared with healthy control participants (z > 2.3; P < .05 corrected). Retrieval success (hits > misses) was associated with hippocampal activation in healthy control participants during relational item recognition and associative recognition conditions, and hippocampal activation was specifically reduced in schizophrenia for recognition of relational but not item-specific information (z > 2.3; P < .05 corrected).Conclusions and relevanceIn this unique, multisite fMRI study, results in the healthy control group supported RiSE construct validity by revealing expected memory effects in PFC and MTL subregions during encoding and retrieval. Comparison of schizophrenic and healthy control participants revealed disproportionate memory deficits in schizophrenia for relational vs item-specific information, accompanied by regionally and functionally specific deficits in dorsolateral PFC and hippocampal activation

Aqueous Humor Dynamics and Its Influence on Glaucoma

The chapter describes the anatomical and functional features of the aqueous humor (AH) dynamics with special focus on pathological changes in glaucoma. The main therapeutic approaches to medically and surgically regulate AH production and outflow are discussed