Supplementation with Calcium Salts of Linoleic and trans-Octadecenoic Acids Improves Fertility of Lactating Dairy Cows   总被引：1，自引：0，他引：1  

SO Juchem  RLA Cerri  M Villaseñor  KN Galvão  RGS Bruno  HM Rutigliano  EJ DePeters  FT Silvestre  WW Thatcher  JEP Santos 《Reproduction in domestic animals》2010,45(1):55-62

Objectives were to evaluate effects of feeding a calcium salt rich in linoleic and trans -octadecenoic acids (LTFA) on synthesis of prostaglandin F_2α based on its metabolite (PGFM), uterine involution and pregnancy rates in lactating dairy cows. Five hundred and eleven Holstein cows were blocked according to parity, body condition score and milk yield in the previous lactation. Primiparous and multiparous cows were randomly assigned to one of the two treatments consisting of calcium salt (2% diet dry matter) of either palm oil (PO) or LTFA from 25 days prepartum to 80 days of lactation. Cows were time-inseminated at 70 ± 3 days postpartum. Feeding LTFA tended (p = 0.08) to decrease the incidence of puerperal metritis (15.1% vs 8.8%). Primiparous cows supplemented with LTFA showed larger increase in plasma PGFM concentration at day 1 postpartum (17018 vs 6897 p m ). Pregnancy rate after first insemination tended (p = 0.07) to be greater at 27 days after insemination (37.9% vs 28.6%), and was greater (p = 0.05) at 41 days after insemination (35.5% vs 25.8%) for cows fed LTFA compared with PO. These results indicate that unsaturated fatty acids fed in a rumen inert form have the potential to modulate reproductive events and improve pregnancy rates in lactating dairy cows.  相似文献   

The Asian‐Melanesian bambusicolous genus Myriodiscus is related to the genus Tympanis,the North American‐European tree pathogen     

Luis Quijada  James K. Mitchell  Eugene Popov  Donald H. Pfister 《Forest Pathology》2019,49(4)

Species of Tympanis are well‐known pathogens in Holarctic forests, but we know little about their relationship to other genera in Tympanidaceae. The genus Myriodiscus, remarkable macroscopically and a possible pathogen on bamboo, has a complicated taxonomic history and has not been conclusively placed phylogenetically. Species of Myriodiscus have been described under two other generic names, Ascotremellopsis and Gelatinomyces, the latter being related to the pathogenic genus Collophorina. There has been no formal synonymy of these three bambusicolous genera or agreement on their systematic positions. We combine accurate micromorphology and DNA sequence data to show the link between Tympanis and Myriodiscus and reveal previously unrecognized features of the latter. These two genera show a type of ascus development unique in the Leotiomycetes. With this new data, we have resolved past confusions over the identity of these fungi, determined their systematic position and have proposed the proper synonymies for Myriodiscus sparassoides and one new combination (M. conus).  相似文献   

The western corn rootworm,a new threat to European agriculture: opportunities for biotechnology?     

Koen Dillen  Paul D Mitchell  Tinne Van Looy  Eric Tollens 《Pest management science》2010,66(9):956-966

BACKGROUND: During the early 1990s, the western corn rootworm, Diabrotica virgifera virgifera Le Conte (WCR), a maize pest, invaded the European continent. The continuous spread of the pest has introduced a new constraint into European maize production. As the damage caused by the invasive species is highly variable and different crop protection (CP) strategies are available, farmers' optimal strategies are not obvious. This study uses a simulation model to assess the competitiveness of different CP strategies in seven Central European countries. RESULTS: Results indicate a high degree of heterogeneity in the profitability of different CP strategies, depending on the production parameters in each country. In general, crop rotation and Bt maize offer the best solutions to farmers, but, in continuous (non‐rotated) maize cultivation, chemical CP options may capture part of the market. For Austrian continuous maize production it is found that not deregulating Bt maize implies that farmers forego revenues of up to €59 ha^?1. CONCLUSIONS: In the presence of WCR, producing maize by an economically sound method requires incorporating country‐ and farm‐specific characteristics into the decision framework. Also, not deregulating Bt maize has direct monetary consequences for many farmers that could influence total maize output and resistance management. Copyright © 2010 Society of Chemical Industry  相似文献   

Uncertainty Analysis of Regional Mercury Exposure     

Seigneur  C.  Lohman  K.  Pai  P.  Heim  K.  Mitchell  D.  Levin  L. 《Water, air, and soil pollution》1999,112(1-2):151-162

A modeling system has been developed to simulate regional environmental exposure to mercury due to atmospheric deposition of mercury to watersheds. The atmospheric fate and transport of mercury is simulated using a comprehensive three-dimensional Eulerian model, the Trace Element Atmospheric Model (TEAM). The aquatic chemistry and bioaccumulation of mercury in fish are simulated using a model of mercury cycling in a lake/watershed system, the Regional Mercury Cycling Model (R-MCM). Fish consumption was derived from a review of available surveys. Previous work focused on an assessment of the environmental and inter-individual variability in key input data (Seigneur et al., 1997a). We address here the uncertainties associated with critical model input variables (e.g., atmospheric deposition velocities, precipitation rate, limnological characteristics). A probabilistic assessment is conducted to propagate the uncertainties in the input data through the modeling system and develop a probability distribution of the human mercury dose that reflects these uncertainties. The standard deviation of the distribution of the calculated human dose is about 50% of the mean value. For the example considered here (i.e., Park Lake in Michigan, U.S.A.), 80% of the uncertainty in the human dose was due to uncertainties in the speciation of mercury air emissions, pH and temperature of the lake, burial velocity of the sediments, and rate of fish consumption.  相似文献   

Net nutrient flux in visceral tissues of lambs fed diets differing in supplemental nitrogen source.     

D W Bohnert  B T Larson  S J Lewis  C J Richards  K C Swanson  D L Harmon  G E Mitchell 《Journal of animal science》1999,77(9):2545-2553

Eight multicatheterized wethers (35.9 +/- .8 kg BW) were used in a replicated 4 x 4 Latin square design to measure N retention and net uptake and release of plasma metabolites across the portal-drained viscera (PDV), hepatic (HEP), and total splanchnic (TS) tissues in response to changes in supplemental N source. Treatments selected to provide different amounts of undegradable intake protein (UIP) were urea, soybean meal (SBM), poultry by-product meal (PBM), and bloodmeal:corn gluten meal (BMCGM; 50:50 CP basis). Diets (urea, SBM, PBM, and BMCGM) contained 12.9, 13.8, 13.6, and 13.2% CP, respectively. Periods were 10 d, with total feces and urine collected on d 7 to 10 and blood sampled on d 10. Wethers were fed at 2% of BW in 12 daily portions. Nitrogen retention was 2.2, 3.3, 4.1, and 4.4 g/d for urea, SBM, PBM, and BMCGM, respectively. Urea had less (P < .01) N retention than SBM, PBM, and BMCGM; SBM had less N retention (P < .01) than PBM and BMCGM. Arterial, portal, and hepatic plasma flows were greater (P < .09) for SBM than for PBM and BMCGM (21 vs 16, 17; 84 vs 72, 72; 105 vs 87, 88 L/h). Portal plasma flow was greater (P < .10) for urea than for SBM, PBM, and BMCGM (85 vs 84, 72, 72 L/h). Portal-drained viscera and TS alpha-amino N (AAN) fluxes were less (P < .05) for PBM than for BMCGM (20.5 vs 26.6 and 7.2 vs 15.1 mmol/h), but TS AAN flux was less (P < .05) for urea than for SBM, PBM, and BMCGM (6.9 vs 16.9, 7.2, 15.1 mmol/h). Portal-drained viscera flux and HEP removal of NH3 N were greater (P < .001) for SBM than for PBM and BMCGM (27.7 vs 19.4, 20.6; -28.1 vs -20.0, -21.4 mmol/h). Gut use was less (P = .07) and HEP and TS fluxes of urea N were greater (P < .01) for SBM than for PBM and BMCGM (-4.92 vs -8.32, -7.93; 25.87 vs 16.54, 20.00; 20.95 vs 8.22, 12.07 mmol/h). These data suggest that PBM and BMCGM improved efficiency of N use compared with urea and SBM by reducing urinary N loss.  相似文献   

Past,present and future land-use in Xishuangbanna,China and the implications for carbon dynamics   总被引：1，自引：0，他引：1  

Hongmei Li  Youxin Ma  T. Mitchell Aide  Wenjun Liu 《Forest Ecology and Management》2008

Land use/land cover change is an important driver of global change and changes in carbon stocks. Estimating the changes in carbon stocks due to tropical deforestation has been difficult, mainly because of uncertainties in estimating deforestation rates and the biomass in the forest that have been cut. In this study, we combined detailed land-use change over a 27-year period based on satellite images and forest inventory data to estimate changes in biomass carbon stocks in the Xishuangbanna prefecture (1.9 million ha) of China. Xishuangbanna is located in southwestern China in the upper watershed of the Mekong River, and the major forest types are tropical seasonal rain forest, mountain rain forest, and subtropical evergreen broadleaf forest. In the past when the region was completely forested the total biomass carbon would have been approximately 212.65 ± 8.75 Tg C. By 1976 forest cover had been reduced to 70%, and in addition many forests had been degraded resulting in a large decrease in the total biomass carbon stocks (86.97 ± 3.70 Tg C). From 1976 to 2003, the mean deforestation rate was 13 722 ha year⁻¹ (1.12%), and this resulted in the loss of 370,494 ha of forest, and by 2003 total biomass carbon stocks had been reduced to 80.85 ± 2.64 Tg C. The annual carbon emissions due to land-use change, mainly forest conversion to agriculture and rubber plantations, were 0.37 ± 0.03 Tg C year⁻¹ between 1976 and 1988 and 0.13 ± 0.04 Tg C year⁻¹ between 1988 and 2003. During the next 20 years, if rubber plantations expand into forests outside of reserves, shrublands, grasslands, and shifting cultivation below 1500 m the total biomass carbon stocks of Xishuangbanna will decrease to 76.45 ± 1.49 Tg C in 2023. This would reflect a loss of 4.13 ± 1.14 Tg C between 2003 and 2023, or an annual loss of 0.21 ± 0.06 Tg C year⁻¹. Alternatively, if rubber plantations only expand into areas of shifting cultivation below 1500 m, and all areas presently in shrublands and grasslands are allowed to recover into secondary forests, total biomass carbon stock of the region would increase to 92.65 ± 3.80 Tg C in 2023. Under this scenario, the growth of existing forests and the expansion of new forests would result in a net sequestration of 0.60 ± 0.06 Tg C year⁻¹. This study demonstrates that the uncertainty of biomass estimates can be greatly reduced if detailed land-use analyses are combined with forest inventory data, and that slight changes in future land-use practices can have large implications for carbon fluxes.  相似文献   

Comparison of wind speeds obtained using numerical weather prediction models and topographic exposure indices for predicting windthrow in mountainous terrain     

S.J. Mitchell  N. Lanquaye-Opoku  H. Modzelewski  Y. Shen  R. Stull  P. Jackson  B. Murphy  J.-C. Ruel 《Forest Ecology and Management》2008

Windthrow prediction models require data concerning stand characteristics and wind exposure. Geographic information system databases typically contain elevation, forest cover, and logging history layers, therefore attributes can be extracted for points distributed across a given landscape. Climate stations in forested areas are rare, but the wind regime at regularly spaced points can be estimated using mesoscale numerical weather prediction models such as MC2, MM5, and RAMS. More traditionally, wind exposure is estimated using topographic exposure indices. Using gridded and cutblock edge segment databases for areas of mountainous terrain in central British Columbia (McGregor) and on southwestern Vancouver Island (WIT), we examined the spatial variability of simulated wind speeds and topographic exposure indices, simple correlations between variables, and the utility of these variables in predicting clearcut edge windthrow. Approximately half of the spatial variability in topographic and wind variables occurred for points spaced within 4 km. After restricting the dataset to one point from every 16 km² panel, mean wind speed was found to be correlated with elevation (0.48, 0.86), but less well with topographic exposure indices (0.17–0.72). Correlations between local winds predicted during strong wind events and topographic exposure indices varied depending on the model used, ranging from non-significant to moderate (0.58). Concordance values for logistic regression models for predicting cutblock edge windthrow improved from 65.0 and 63.8 for base models with height and stand variables, to 70.2 and 68.2 with the addition of topographic exposure indices and extreme wind measures, for McGregor and WIT, respectively.  相似文献   

Projected long-term response of Southeastern birds to forest management     

Michael S. Mitchell  Melissa J. Reynolds-Hogland  Michelle L. Smith  Petra Bohall Wood  John A. Beebe  Patrick D. Keyser  Craig Loehle  Christopher J. Reynolds  Paul Van Deusen  Don White Jr. 《Forest Ecology and Management》2008

Numerous studies have explored the influence of forest management on avian communities empirically, but uncertainty about causal relationships between landscape patterns and temporal dynamics of bird communities calls into question how observed historical patterns can be projected into the future, particularly to assess consequences of differing management alternatives. We used the Habplan harvest scheduler to project forest conditions under several management scenarios mapped at 5-year time steps over a 40-year time span. We used empirical models of overall avian richness, richness of selected guilds, and probability of presence for selected species to predict avian community characteristics for each of the mapped landscapes generated for each 5-year time step for each management scenario. We then used time series analyses to quantify relationships between changes in avian community characteristics and management-induced changes to forest landscapes over time. Our models of avian community and species characteristics indicated habitat associations at multiple spatial scales, although landscape-level measures of habitat were generally more important than stand-level measures. Our projections showed overall avian richness, richness of Neotropical migrants, and the presence of Blue-gray Gnatcatchers and Eastern Wood-pewees varied little among management scenarios, corresponding closely to broad, overall landscape changes over time. By contrast, richness of canopy nesters, richness of cavity nesters, richness of scrub-successional associates, and the presence of Common Yellowthroats showed high temporal variability among management scenarios, likely corresponding to short-term, fine-scale changes in the landscape. Predicted temporal variability of both interior-forest and early successional birds was low in the unharvested landscape relative to that in the harvested landscape. Our results also suggested that early successional species can be sensitive to both availability and connectivity of habitat on the landscape. To increase or maintain the avian diversity, our projections indicate that forest managers need to consider landscape-scale configuration of stands, maintaining a spatially heterogeneous distribution of age classes. Our findings suggest which measures of richness or species presence may be appropriate indicators for monitoring effects of forest management on avian communities, depending on management objectives.  相似文献   

The ionic composition of the streams of the mid-Murrumbidgee River: Implications for the management of downstream salinity   总被引：1，自引：0，他引：1  

M.K. Conyers  I. Hume  G. Summerell  D. Slinger  M. Mitchell  R. Cawley   《Agricultural Water Management》2008,95(5):598-606

The Murrumbidgee River catchment is a major region of both dryland and irrigated agricultural production in eastern Australia. The salinity of water in the lower reaches of the river is the subject of concern; changing land management upstream is one option to minimise accessions of salt to the river but this must be done in a way that provides an adequate quantity of water for downstream users and the environment.

We examined 30 years of sporadic data on the ionic composition of water for 7 subcatchments contributing to the mid-Murrumbidgee River and for 2 gauging stations on the river itself. Despite the common local presumption that salinity, measured as electrical conductivity (EC), is primarily due to NaCl from cyclic marine salt, we found that NaCl was the dominant salt in only some streams. The presence of HCO₃⁻'s of Ca²⁺ and Mg²⁺ in all streams, and their dominance in 2 streams, indicates that mineral weathering is also a major contributor to the salt load of water in the catchment. However, Ca²⁺ and Mg²⁺ bicarbonates have limited solubility and so their concentrations will not become a cause of osmotic stress when the water is used for drinking or irrigation. Therefore, in our efforts to prioritise lower order catchments of the Murrumbidgee River for changed land management, it will be necessary to examine the nature of the salts they discharge, not just EC. By distinguishing between Cl⁻/Na⁺ dominated streams and Ca²⁺, Mg²⁺/HCO₃⁻ dominated streams we can refine our search for sources of osmotic stress which might potentially worsen with time. This will enable us to target particular land management units so as to obtain the maximum reduction in downstream salinity with a minimal decrease in flow volume and minimal area of land undergoing changed landuse.  相似文献   

Characterization of starch morphology,composition, physicochemical properties and gene expressions in oat     

Zheng Ke  Jiang Qian-tao  Wei Long  Zhang Xiao-wei  Ma Jian  Chen guo-yue  Wei Yuming  Mitchell Fetch Jennifer  Lu Zhen-xiang  Zheng You-liang 《农业科学学报》2015,14(1):20-28

Starch is the major carbohydrate in oat(Avena sativa L.) and starch formation requires the coordinated actions of several synthesis enzymes. In this study, the granule morphology, composition and physicochemical properties of oat starch, as well as the expressions of starch synthesis genes were investigated during oat endosperm development. Under the scanning electron microscopy(SEM), we observed that the unique compound granules were developed in oat endosperms at 10 days post anthesis(DPA) and then fragmented into irregular or polygonal simple granules from 12 DPA until seed maturity. The amylose content, branch chain length of degree of polymerization(DP=13–24), gelatinization temperature and percentage of retrogradation were gradually increased during the endosperm development; whereas the distribution of short chains(DP=6–12) were gradually decreased. The relative expressions of 4 classes of 13 starch synthesis genes characterized in this study indicated that three expression pattern groups were significantly different among gene classes as well as among varied isoforms, in which the first group of starch synthesis genes may play a key role on the initiation of starch synthesis in oat endosperms.  相似文献