A long standing ecological paradigm suggests that diverse plant communities should be more resistant to weed invasion compared with plant communities that have few species. Data from three separate ...studies were used to test the hypothesis that increased forage species diversity reduces weed invasion in pasture communities. The first study measured weed invasion in experimentally constructed pasture communities containing 1–15 species. A second experiment conducted in the greenhouse involved sowing a common perennial weed species, curly dock (
Rumex crispus), into forage mixtures with 5 or 10 different forage species and three monocultures. The third study investigated the relationship between weed abundance and forage diversity in 37 pastures surveyed across the northeastern United States. Consistent negative relationships between forage species diversity and weed abundance were found. The causal mechanisms explaining the negative relationships between forage diversity and weed invasion were difficult to delineate since diversity was often correlated with highly productive pasture communities. The results suggest that maintaining both productive pasture communities (>150
g
m
−2 of aboveground biomass) and an evenly distributed array of forage species should be combined to effectively reduce weed invasion. Managing pastures for increased forage species diversity could be a useful cultural control method for weeds. Increasing the diversity of forage plants also has other ecosystem benefits to pasture communities (e.g., greater primary production, stability) beyond that of weed suppression.
Integrating trees into pastures, a practice known as silvopasture, may benefit livestock in the summertime through the provision of shade. The purpose of this project was to compare the behavioral ...patterns of sheep grazing in silvopastures and open pastures. Black walnut (
L.) and honeylocust (
L.) based silvopasture systems were compared with open pastures in a randomized complete block design with three blocks over two summers. Behavior measures were recorded within a replicate within a week, and these measures were taken sequentially within three experimental periods. Ewe lambs (
= 3) within each experimental unit were equipped with a wideband audio-recording device to detect prehension events. Time-lapse cameras documented sheep behavior every 60 s. In the silvopastures, the lambs spent over 90% of daylight hours within shade from trees. Lambs in silvopastures spent more time lying down than animals in the open pastures (
≤ 0.01), while lambs in the open pastures spent more than 2 h longer each day standing (
< 0.0001). Lambs in the black walnut silvopastures spent more time grazing (488 ± 14 min · d
) than lambs in the honeylocust silvopastures (438 ± 14 min · d
;
= 0.0493) and lambs in the open pastures (417 ± 14 min · d
;
= 0.0026). There was no difference in grazing time for lambs in the latter two systems (
= 0.5597). Spectral analysis of the imagery revealed that the lambs in the black walnut silvopastures grazed more frequently than the lambs in the other systems for both years. The acoustic analysis, though limited by recorder durability to 47 complete recordings, revealed no difference in total bites taken per day (
≥ 0.7222) or in the morning (
≥ 0.2069), afternoon (
≥ 0.5816), and evening periods (
≥ 0.9337). Silvopastures provide an opportunity to improve lamb comfort in the summer.
Compared with traditional cropping systems, integrated crop–livestock systems have shown greater efficiency in improving soil quality and crop yield. The objective of this study was to determine how ...an integrated crop–livestock system affected soil properties and corn (Zea mays L.) yield when compared with continuous corn (CC). The study was conducted from 2004–2008 on a large-scale research farm located near Pana, IL, USA. We evaluated the following soil and crop variables: soil organic matter (SOM) fractions, total nitrogen (TN) and total organic carbon (TC), soil microbial biomass carbon (SMBC), water aggregate stability, soil penetration resistance (PR), and corn yield. Three treatments were used in this study: winter cover crops (WCCs) and cool-season pastures (CSP), considered integrated system treatments and a nonintegrated CC monoculture. In the integrated system, CSP and WCC treatments combined, had significantly higher TN (P = 0.0926) than CC. Water aggregate stability was also higher in the integrated system (P = 0.0039). Greater percentages of TC and TN were represented by particulate organic matter (POM) POM-N and POM-C in the WCC treatment, followed by CSP, and CC. The PR for CSP (928 kPa) was not significantly different than WCC (921 kPa). However, both were significantly different than CC (655 kPa). Averaged across years, corn grain yield for WCC (11.5 Mg ha–1) was significantly higher than CC (10.8 Mg ha–1) (P = 0.0780). These results confirm that WCC and CSP used within integrated crop–livestock systems should improve soil quality, SOM dynamics, and crop yield despite moderate soil compaction caused from cattle presence.
Background
Medication discontinuation is a common result of bariatric surgery. The influence of individual patient characteristics and surgical outcomes on overall and specific medication ...discontinuation is not well understood. The purpose of the current study was to assess changes in medication use and identify individual characteristics and surgical outcomes associated with medication discontinuation among bariatric patients.
Methods
The patients included in the current study received bariatric surgery from the Northern Colorado Surgical Associates of Fort Collins, Colorado, USA, between October 2007 and September 2010. Demographic, weight, health, and medication data from 400 patients with at least one 6- or 12-month post-operative appointment were extracted from the Bariatric Outcome Longitudinal Database. Multivariate regression analyses were used to investigate how patient factors affect total medication use over time, use of medications grouped by co-morbidity post-operatively, and use of specific medication classes post-operatively.
Results
Baseline co-morbidities, particularly type 2 diabetes, male sex, and Roux-en-Y gastric bypass surgery were significantly associated with decreased total medication use following surgery. Weight loss, systemic disease, sex, baseline co-morbidities, surgical complications, and race were significantly associated with continued use of specific medications following surgery.
Conclusions
Bariatric surgery can help patients with certain characteristics discontinue medications but is not effective for all patients. Baseline health, sex, race, bariatric procedure, surgical complications, and post-operative weight loss may affect how bariatric patients' medication use changes pre-operatively to post-operatively.
Dietary sulfur amino acid restriction (SAAR) protects against diet-induced obesity, extends healthspan, and coincides with an overall reduction in hepatic protein synthesis. To explore the ...underpinnings of SAAR-induced slowed growth and its impact on liver metabolism and proteostasis, we resolved changes in hepatic mRNA and protein abundances and compared synthesis rates of individual liver proteins. To achieve this, adult male mice were provided deuterium-labeled drinking water while freely consuming either a regular-fat or high-fat diet that was SAA restricted. Livers from these mice and their respective dietary controls were used to conduct transcriptomic, proteomic, and kinetic proteomic analyses. We found that remodeling of the transcriptome by SAAR was largely agnostic to dietary fat content. Shared signatures included activation of the integrated stress response alongside alterations in metabolic processes impacting lipids, fatty acids, and amino acids. Changes to the proteome correlated poorly with the transcriptome, and yet, functional clustering of kinetic proteomic changes in the liver during SAAR revealed that the management of fatty acids and amino acids were altered to support central metabolism and redox balance. Dietary SAAR also strongly influenced the synthesis rates of ribosomal proteins and ribosome-interacting proteins regardless of dietary fat. Taken together, dietary SAAR alters the transcriptome and proteome in the liver to safely manage increased fatty acid flux and energy use and couples this with targeted changes in the ribo-interactome to support proteostasis and slowed growth.
Crop and livestock production are rarely integrated together in modern farming systems. Reintegrating crops with livestock production has been shown to produce many agronomic and environmental ...benefits. The objective of this study was to evaluate how an integrated crop-livestock system would influence weed biomass and weed species composition compared with a conventional, continuous corn (Zea mays L.) cropping system. The experimental farming system used in this study was established on a 90-ha site near Pana, IL, in 2002. The integrated system included two phases: (i) a corn and oat (Avena sativa L.) cash crop rotation, grown in summer, and (ii) post-harvest grazing of corn stover with annual cover crops. Over a 4-yr period (2004-2007), weed biomass was approximately 4.5 times higher in the conventional system (8.4 g m-2) compared with the integrated system (1.8 g m-2). Weed species composition was affected by the integrated system and showed a temporal disjunction between the time of year and weed life history. Surprisingly, cattle grazing on cropland had little effect on weed biomass or species composition. The primary drivers that suppress weed biomass and change species composition appear to be use of crop rotation and annual cover crops within the integrated system. Wider adoption of integrated crop-livestock systems, such as the one used in this study, should reduce reliance on herbicides compared with more conventional cropping systems.
Abstract
The integration of trees into pasture systems can have variable effects on forage and animal growth. Some reports of these systems have indicated that animal gains are similar or better even ...when tree presence lowers forage yield. Forage production and animal performance were compared in black walnut (Juglans nigra L.)-based and honeylocust (Gleditisia triacanthose L.)-based silvopasture systems and open pastures in a randomized complete block design with three blocks over three summers. Cool season-based, mixed grass pastures were rotationally stocked with four to seven lambs depending on available forage. A rising plate meter was used to estimate pre- and post-graze forage mass. Forage samples of the mixed sward were collected and analyzed for nitrogen (N) and neutral detergent fiber (NDF) concentrations. Species percent cover was estimated using a modified Daubenmire approach at the same 12 points within each experimental unit every 4 wk during the study. Pre-graze herbage mass was similar (P = 0.0717) in honeylocust silvopastures (5020 ± 30 kg·ha−1) and open pastures (4930 ± 30 kg·ha−1) and lowest (P < 0.0001) in the black walnut silvopastures (3560 ± 30 kg·ha−1). Forages in the black walnut and honeylocust silvopastures had similar (P = 0.4867) N concentrations (23.3 ± 0.4 and 23.9 ± 0.4 g·kg−1, respectively), which was greater (P ≤ 0.0003) than that of the forages in the open pastures (21.0 ± 0.4 g·kg−1). Forages in the honeylocust silvopasture had lower (P ≤ 0.0042) NDF concentrations (507 ± 3 g·kg−1) than forages in the black walnut silvopasture and open pastures (mean = 525 ± 3 g·kg−1). Forage species present in the black walnut silvopastures differed from those present in the open and honeylocust systems, which had similar composition. Despite differences in stocking rates, total lamb weight gains per system did not differ (P ≥ 0.7592) among black walnut, honeylocust, and open pasture systems (10 ± 2, 12 ± 2, and 10 ± 2 kg·d−1, respectively). Silvopasture practices can improve land productivity when incorporated into cool season forage pastures.
Microorganisms are largely responsible for soil nutrient cycling and energy flow in terrestrial ecosystems. Although soil microorganisms are affected by topography and grazing, little is known about ...how these two variables may interact to influence microbial processes. Even less is known about how these variables influence microorganisms in systems that contain large populations of free-roaming ungulates. In this study, we compared microbial biomass size and activity, as measured by in situ net N mineralization, inside and outside 35- to 40-year exclosures across a topographic gradient in northern Yellowstone National Park. The objective was to determine the relative effect of topography and large grazers on microbial biomass and nitrogen mineralization. Microbial C and N varied by almost an order of magnitude across sites. Topographic depressions that contained high plant biomass and fine-textured soils supported the greatest microbial biomass. We found that plant biomass accurately predicted microbial biomass across our sites suggesting that carbon inputs from plants constrained microbial biomass. Chronic grazing neither depleted soil C nor reduced microbial biomass. We hypothesize that microbial populations in grazed grasslands are sustained mainly by inputs of labile C from dung deposition and increased root turnover or root exudation beneath grazed plants. Mineral N fluxes were affected more by grazing than topography. Net N mineralization rates were highest in grazed grassland and increased from dry, unproductive to mesic, highly productive communities. Overall, our results indicate that topography mainly influences microbial biomass size, while mineral N fluxes (microbial activity) are affected more by grazing in this grassland ecosystem.
There is an emerging recognition that invasibility is not an intrinsic community trait, but is a condition that fluctuates from interactions between environmental forces and residential characters. ...Elucidating the spatiotemporal complexities of invasion requires inclusion of multiple, ecologically variable factors within communities of differing structure. Water and nutrient amendments, disturbance, and local composition affect grassland invasibility but no study has simultaneously integrated these, despite evidence that they frequently interact. Using a split-plot factorial design, we tested the effects of these factors on the invasibility of C₃ pasture communities by smooth pigweed Amaranthus hybridus L., a problematic C₄ forb. We sowed seeds and transplanted 3-week old seedlings of A. hybridus into plots containing monocultures and mixtures of varying composition, subjected plots to water, soil disturbance, and synthetic bovine urine (SBU) treatments, and measured A. hybridus emergence, recruitment, and growth rate. Following SBU addition, transplanted seedling growth increased in all plots but differed among legume and nonlegume monocultures and mixtures of these plant types. However, SBU decreased the number and recruitment rate of emerged seedlings because high residential growth reduced light availability. Nutrient pulses can therefore have strong but opposing effects on invasibility, depending on when they coincide with particular life history stages of an invader. Indeed, in SBU-treated plots, small differences in height of transplanted seedlings early on produced large differences in their final biomass. All facilitative effects of small-scale disturbance on invasion success diminished when productivity-promoting factors were present, suggesting that disturbance patch size is important. Precipitation-induced invasion resistance of C₃ pastures by a C₄ invader was partly supported. In grazed grasslands, these biotic and environmental factors vary across scales and interact in complex ways to affect invasibility, thus a dynamic patch mosaic of differential invasion resistance likely occurs in single fields. We propose that disturbance patch size, grazing intensity, soil resource availability, and resident composition are inextricably linked to grassland invasions and comment on the utility of community attributes as reliable predictors of invasibility. Lastly, we suggest temporal as well as spatial coincidences of multiple invasion facilitators dictate the window of opportunity for invasion.
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