Evaluating the effects of supplemental B vitamins in practical swine diets during the starter and grower-finisher periods--a regional study

Two experiments were conducted to evaluate dietary fortification levels of a B vitamin pre-mix for starter and grower-finisher pigs on subsequent performance responses. The objective was to determine whether the modern pig requires higher dietary levels of B vitamins than estimated by the NRC (1998). Both experiments added fat-soluble vitamins at the requirement levels (NRC, 1998) in all diets, whereas the B vitamins were added at 0, 100, 200, or 400% of the total NRC (1998) requirement levels for the starter and grower pig. Indigenous vitamin contributions from the feed grains were not included in the estimates. Each station used the same vitamin premixes but incorporated its own grain sources in the diets. The first experiment was conducted across 7 stations (Indiana, Ohio, Oklahoma, Michigan, Missouri, Nebraska, Texas) and involved 660 pigs in a randomized complete block design in 30 replicates. Complex nursery diets were fed in 2 phases. The first phase (0 to 14 d postweaning) and second phase (15 to 35 d postweaning) diets were formulated to Lys (total) levels of 1.50 and 1.30%, respectively. The results demonstrated no performance response to addition of B vitamins from 0 to 14 d post-weaning, but performances increased quadratically (P < 0.01) to the 100% NRC level from 14 to 35 d postweaning and for the overall 35-d period. The second experiment was conducted across 3 stations (Ohio, Nebraska, and South Dakota) and involved 216 pigs in a randomized complete block design in 10 replicates. Corn-soybean meal mixtures were fed in 3 phases formulated to total Lys levels of 1.30% (23 to 55 kg of BW), 1.00% (55 to 85 kg of BW), and 0.78% (85 to 120 kg of BW). Pig performances increased (P < 0.01) to the 100% B vitamin level from 23 to 85 kg of BW, but there was no response to any level from 85 to 120 kg of BW. Carcass measurements demonstrated a greater LM area (P < 0.01) and a lower backfat depth (P < 0.01) to the 100% B vitamin level. One station evaluated an additional treatment (3 replicates) in which each replicate was fed a fifth diet containing the 100% dietary level of B vitamins from 23 to 85 kg of BW whereupon the B vitamins were removed from 85 to 120 kg of BW. This removal did not reduce pig performance responses for the final period or for the overall period. The results demonstrated that supplementation of B vitamins at the 100% total NRC levels for starter and grower pigs was sufficient to meet their needs, and there was no further improvement to or deleterious effect to greater dietary levels.     

Sediment organic carbon integrates changing environmental conditions to predict benthic assemblages in shallow Arctic seas

相似文献   

Prescribed burning and mechanical thinning effects on belowground conditions and soil respiration in a mixed-conifer forest,California

Soil respiration (R_S) is a major carbon pathway from terrestrial ecosystems to the atmosphere and is sensitive to environmental changes. Although commonly used mechanical thinning and prescribed burning can significantly alter the soil environment, the effect of these practices on R_S and on the interactions between R_S and belowground characteristics in managed forests is not sufficiently understood. We: (1) examined the effects of burning and thinning treatments on soil conditions, (2) identified any changes in the effects of soil chemical and physical properties on R_S under burning and thinning treatments, and (3) indirectly estimated the changes in the autotrophic soil respiration (R_A) and heterotrophic soil respiration (R_H) contribution to R_S under burning and thinning treatments. We conducted our study in the Teakettle Experimental Forest where a full factorial design was implemented with three levels of thinning, none (N), understory thinning (U), and overstory thinning (O; September to October 2000 for thin burn combination and June and July 2001 for thin only treatments) and two levels of burning, none (U) and prescribed burning (B; fall of 2001). R_S, soil temperature, soil moisture, litter depth, soil total nitrogen and carbon content, soil pH, root biomass, and root nitrogen (N) concentration were measured between June 15 and July 15, 2002 at each plot. During this period, soil respiration was measured three times at each point and averaged by point. When we assumed the uniform and even contribution of R_A and R_H to R_S in the studied ecosystem without disturbances and a linear relationship of root N content and R_A, we calculated the contributions of R_A to R_S as 22, 45, 53, 48, and 45% in UU, UO, BN, BU, and BO, respectively. The results suggested that after thinning, R_S was controlled more by R_H while after burning R_S was more influenced by R_A. The least amount of R_S variation was explained by studied factors under the most severe treatment (BO treatment). Overall, root biomass, root N concentration, and root N content were significantly (p < 0.01) correlated with soil respiration with correlation coefficients of 0.37, −0.28, and 0.29, respectively. This study contributes to our understanding of how common forestry management practices might affect soil carbon sequestration, as soil respiration is a major component of ecosystem respiration.     

绿壳蛋鸡青年鸡疑似心包积液——肝炎综合征的实验室诊断

2017年，在河北省涿鹿县某山间林下饲养的60～80日龄绿壳蛋鸡青年鸡突然发生大量死亡，根据其临床症状以及剖检变化初步怀疑为心包积液——肝炎综合征（hvdroericardium hepatitis syndrome，HHS）。为了进一步确诊，选择发病死亡典型病例采集样品进行细菌和病毒的分离、培养、鉴定，以及10周龄SPF鸡致病试验。结果表明，分离到3株大肠杆菌，但接种SPF鸡未出现典型临床症状和发病死亡；利用电镜观察到直径为60～80nm的圆形病毒，该病毒能够凝集大鼠红细胞；病毒分离株引起SPF鸡出现典型的心包积液一肝炎的剖检变化；经琼脂扩散试验鉴定该病毒为禽Ⅰ群腺病毒4型。     

Mapping radiation interception in row-structured orchards using 3D simulation and high-resolution airborne imagery acquired from a UAV

This study was conducted to model the fraction of intercepted photosynthetically active radiation (fIPAR) in heterogeneous row-structured orchards, and to develop methodologies for accurate mapping of the instantaneous fIPAR at field scale using remote sensing imagery. The generation of high-resolution maps delineating the spatial variation of the radiation interception is critical for precision agriculture purposes such as adjusting management actions and harvesting in homogeneous within-field areas. Scaling-up and model inversion methods were investigated to estimate fIPAR using the 3D radiative transfer model, Forest Light Interaction Model (FLIGHT). The model was tested against airborne and field measurements of canopy reflectance and fIPAR acquired on two commercial peach and citrus orchards, where study plots showing a gradient in the canopy structure were selected. High-resolution airborne multi-spectral imagery was acquired at 10?nm bandwidth and 150?mm spatial resolution using a miniaturized multi-spectral camera on board an unmanned aerial vehicle (UAV). In addition, simulations of the land surface bidirectional reflectance were conducted to understand the relationships between canopy architecture and fIPAR. Input parameters used for the canopy model, such as the leaf and soil optical properties, canopy architecture, and sun geometry were studied in order to assess the effect of these inputs on canopy reflectance, vegetation indices and fIPAR. The 3D canopy model approach used to simulate the discontinuous row-tree canopies yielded spectral RMSE values below 0.03 (visible region) and below 0.05 (near-infrared) when compared against airborne canopy reflectance imagery acquired over the sites under study. The FLIGHT model assessment conducted for fIPAR estimation against field measurements yielded RMSE values below 0.08. The simulations conducted suggested the usefulness of these modeling methods in heterogeneous row-structured orchards, and the high sensitivity of the normalized difference vegetation index and fIPAR to background, row orientation, percentage cover and sun geometry. Mapping fIPAR from high-resolution airborne imagery through scaling-up and model inversion methods conducted with the 3D model yielded RMSE error values below 0.09 for the scaling-up approach, and below 0.10 for the model inversion conducted with a look-up table. The generation of intercepted radiation maps in row-structured tree orchards is demonstrated to be feasible using a miniaturized multi-spectral camera on board UAV platforms for precision agriculture purposes.     

The effect of conditions of storage on the respiration of apples. V. The relationship between temperature,rate of respiration,and composition of the internal atmosphere of the fruit

Change of rate of production of CO₂ leads to change in the composition of the internal atmosphere of apple fruits, and therefore the gross effect of temperature is a complex phenomenon which involves change in other parameters of the cellular environment.

An attempt has been made to determine the effect of temperature alone on the cellular rate of respiration, but it does not appear to be possible to do this for a bulky organ.

Over the range from 0° to 12 °C, the concentration of CO₂ in the intercellular spaces of an apple varied directly with the rate of production of CO₂, thus satisfying Fick’s law. Temperature appeared to have no effect on the porosity of the skin.     

Pesticides in cereal production

A cereal grower will normally attempt to maximise his returns from resources used without prejudicing the future. Historically, for the control of weeds, pests and diseases growers have preferred husbandry methods and the use of ‘resistant’ varieties. Economic pressures, technical developments and subsequent changes in farming systems demand more reliance on pesticides. The adoption of the Common Agricultural Policy and the relatively higher cereal prices improve the cost: benefit ratio from their more extensive use. Additionally, quality standards arising directly or indirectly from EEC legislation, where these can be influenced by pesticide application, will further encourage their routine application. In the longer term, increased fixed costs will encourage the grower to insure against crop losses by the use of prophylactic pesticide applications where appropriate. New systems of production to reduce fixed costs will be adopted, probably involving further use of pesticides. Growers will always wish to contain variable costs as far as is possible: as better forecasting of disease and pest epidemics is developed prophylactic treatments will be discarded. Examples of the economic benefits or penalties of adopting alternatives to pesticides are given.     

从家蝇幼虫饲料残渣中分离提取生物活性物质的研究(简报)

家蝇(Musca domastica vicina)幼虫在生长发育过程中,能分泌有广泛抑菌作用的活性物质。这种活性物质对多种严重的农作物病害亦有显著抑制作用,而对有益生物无害。深入研究这种活性物质的分离提纯方法、理化性质、结构特点、活性特征等,对生物合成或仿生合成新一代完全无公害农药,对家蝇在生态系的作用和综合利用,都有重要理论意义和实用价值,本文简报近几年作者从家蝇幼虫饲料残渣中提取分离这种活性物质的方法及其性质的初步探讨。1 材料与方法