A framework for evaluation of on-farm mastitis diagnostics in Australia

Numerous culture-based diagnostics are available on the Australian and international markets for on-farm detection of bacterial pathogens in milk. Use of such diagnostics may provide an opportunity to improve the prudent use of antimicrobials in udder health management. Farms are low-resource settings in terms of diagnostic microbiology capacity. The World Health Organisation has identified criteria for the evaluation of diagnostic tests in low resource settings based on Accuracy, Sensitivity, Specificity, User-friendliness, being Rapid or Robust, Equipment-free and being Deliverable (ASSURED). Here, we review how those criteria can be interpreted in the context of microbiological diagnosis of mastitis pathogens, and how on-farm diagnostics that are currently available in Australia perform relative to ASSURED criteria. This evaluation identifies multiple trade-offs, both with regard to scientific criteria and with regards to convenience criteria. More importantly, the purpose of testing may differ between farms, and test performance should be evaluated relative to its intended use. The ability of on-farm mastitis diagnostics to inform mastitis treatment decision-making in a timely and cost-effective manner depends not just on test characteristics but also on farm-specific pathogen prevalence, and on the farm enterprise's priorities and the farm manager's potential courses of action. With most assay evaluations to date conducted in professional laboratories, there is a surprising dearth of information on how well any of the diagnostic tests perform on-farm and, indeed, of the on-farm decision-making processes that they aim to inform.     

土壤保持耕作——全球农业可持续发展优先领域

 从农业活动对全球变化以及对农业可持续发展的影响进而导致全球性土壤保持需求的迫切性增加出发，追踪了国外土壤保持耕作领域的研究和发展动态；对中国该领域研究发展现状和研究水平，从时间、深度、方法、生产应用等方面与国外进行了比较分析。中国是一个水土流失和耕地退化严重的农业大国，而从全球统计数字来看，中国土壤保持耕作面积目前仅占全球保持耕作面积的0.2%，仅占全国耕地面积的0.1%， 其现状与中国耕地资源和环境的继续退化以及对土壤保持耕作需求的增加极不相符。加强中国土壤保持耕作系统研究和土壤保持耕作"节能固碳"长期建设不仅对中国而且对全球变化及农业可持续发展具有重大意义。鉴于中国土壤保持耕作领域研究和发展所存在的不足和所面临的更大挑战，以及该领域研究涉及到复杂的农业系统"耕作管理-生物过程-环境变化"相互作用及其系统能流-碳流循环过程，尤其农业生态系统碳汇/源估量尚存在诸多不确定性因素等科学问题，有必要运用综合的系统性研究分析方法，借助国外长期试验和理论研究经验，以及系统模型模拟研究手段等多学科和交叉学科知识，加速提升中国土壤保持耕作领域的科研实力和水平，为实现碳汇/源科学调控管理、减缓农业对温室效应贡献、促进农业可持续发展提供科学依据。     

农业土壤表面不平度和测量与分析

农业土壤表面不平度与土壤风蚀、行走装置的相互作用和田间土壤含水量测定分布图等方面具有极其重要的作用.本文利用激光式不平度测试仪测定犁耕耕地地面、圆盘耙地地面和驱动耙耙地地面的不平度,测定地面不平度沿着三个方向进行,即平行于耕作方向、倾斜于耕作方向和垂直于耕作方向.对每一种地面不平度的RMS值、相关长度和自相关函数进行了分析,结果表明对于短的地块,可用单一尺度来表征地表不平度的特征,地表不平度特征属于指数相关函数,RMS高度和自相关长度具有明显的相关性.对于长的地块,平整的农业地表不平度具有分形性或多尺度性,其自相关函数是一种分形过程.     

Dust storm erosion and its impact on soil carbon and nitrogen losses in northern China

There is increased awareness of the environmental impacts of soil carbon (C) and nitrogen (N) losses through wind erosion, especially in areas heavily affected by dust storm erosion. This paper reviews the recent literature concerning dust storm-related soil erosion and its impact on soil C and N losses in northern China. The purpose of our study is to provide an overview of the area of erosion-affected soils and to estimate the magnitude of soil C and N losses from farmland affected by dust storm erosion.According to the second national soil erosion remote-sensing survey in 2000, the area affected by wind erosion was 1.91 million km², accounting for 20% of the total land area in China. This area is expanding quickly as the incidence of heavy dust storms has greatly increased over the last five decades, mainly as a result of the intensification of soil cultivation. The economic and ecological damage caused by wind erosion is considerable. Heavily affected areas show a loss of nutrients and organic carbon in soils and the heavily degraded soils are much less productive. Compared with the non-degraded soil, the C and N contents in degraded soils have declined by 66% and 73%, respectively. The estimated annual losses per cm toplayer of soil C and N by dust storm erosion in northern China range from 53 to 1044 kg ha^− 1 and 5 to 90 kg ha^− 1, respectively. Field studies suggest that soil losses by wind erosion can be reduced by up to 79% when farmers shift from conventional soil tillage methods to no-till. Thus shifting to no-till or reduced tillage systems is an effective practice for protecting soil and soil nutrients. Our study indicates that soil conservation measures along with improved soil fertility management measures should be promoted in dry-land farming areas of northern China. As erosion is a major mechanism of nutrient withdrawal in these areas, we plead for the development of accurate methods for its assessment and for the incorporation of erosion, as a nutrient output term, in nutrient budget studies.     

Dietary nitrate supplementation reduces methane emission in beef cattle fed sugarcane-based diets

The objective of this study was to determine the effect of dietary nitrate on methane emission and rumen fermentation parameters in Nellore × Guzera (Bos indicus) beef cattle fed a sugarcane based diet. The experiment was conducted with 16 steers weighing 283 ± 49 kg (mean ± SD), 6 rumen cannulated and 10 intact steers, in a cross-over design. The animals were blocked according to BW and presence or absence of rumen cannula and randomly allocated to either the nitrate diet (22 g nitrate/kg DM) or the control diet made isonitrogenous by the addition of urea. The diets consisted of freshly chopped sugarcane and concentrate (60:40 on DM basis), fed as a mixed ration. A 16-d adaptation period was used to allow the rumen microbes to adapt to dietary nitrate. Methane emission was measured using the sulfur hexafluoride tracer technique. Dry matter intake (P = 0.09) tended to be less when nitrate was present in the diet compared with the control, 6.60 and 7.05 kg/d DMI, respectively. The daily methane production was reduced (P < 0.01) by 32% when steers were fed the nitrate diet (85 g/d) compared with the urea diet (125 g/d). Methane emission per kilogram DMI was 27% less (P < 0.01) on the nitrate diet (13.3 g methane/kg DMI) than on the control diet (18.2 g methane/kg DMI). Methane losses as a fraction of gross energy intake (GEI) were less (P < 0.01) on the nitrate diet (4.2% of GEI) than on the control diet (5.9% of GEI). Nitrate mitigated enteric methane production by 87% of the theoretical potential. The rumen fluid ammonia-nitrogen (NH(3)-N()) concentration was significantly greater (P < 0.05) for the nitrate diet. The total concentration of VFA was not affected (P = 0.61) by nitrate in the diet, while the proportion of acetic acid tended to be greater (P = 0.09), propionic acid less (P = 0.06) and acetate/propionate ratio tended to be greater (P = 0.06) for the nitrate diet. Dietary nitrate reduced enteric methane emission in beef cattle fed sugarcane based diet.     

Expression of MHC-I and -II in Uterine Tissue from Early Pregnant Bitches

The aim of the study was to investigate the expression of major histocompatibility complex (MHC)-I and -II in uterine tissues from pregnant and non-pregnant bitches, taken at different time periods after mating. The pregnant bitches were ovariohysterectomized during the pre-implantation (group 1, n = 4), implantation (group 2, n = 7) and placentation stage (group 3, n = 7). Non-pregnant animals in diestrus served as controls (group 4, n = 7). The expression of MHC- I and -II in salpinx, apex, middle horn, corpus uteri and at implantation sites was investigated by immunohistochemistry as well as qualitative and quantitative RT-PCR; MHC-I mRNA was detected in all tissues and with quantitative RT-PCR, and no significant changes were detected until placentation. Immunohistologically, at the apex and corpus site, the average number of MHC-II positive cells increased from the pre-implantation to the post-implantation stage (apex: 1.54 ± 1.21 to 3.82 ± 2.93; corpus: 1.62 ± 1.9 to 5.04 ± 4.95; p < 0.05). The greatest numbers of MHC-II positive cells were observed at placentation sites (6.64 ± 5.9). In parallel, a marked increase in the relative mRNA expression of MHC-II in uterine tissues was assessed from the pre-implantation to the placentation stage (relative to Glycerinaldehyd-3-phosphate-Dehydrogenase (GAPDH): 6.9 ± 9.5, 8.4 ± 5.8, p > 0.05). Immunohistologically, in the salpinx, significantly greater numbers of MHC-II positive cells were found in the tissues of pregnant animals than in the control group (p < 0.05). It is proposed that the increase in MHC-II is pregnancy-related, even though the impact on maintenance of canine pregnancy is still unclear.     

Selective uprooting by weed harrowing on sandy soils

Uprooting by weed harrowing and the potential of the uprooting process for selective weed control at early crop growth stages was studied. Effects of working depth, seed depth, soil moisture content and working speed on uprooting of Lolium perenne L., Lepidium sativum L. and Chenopodium quinoa Willd. were investigated in laboratory harrowing experiments on a sandy soil. Harrowing uprooted on average 51% of the emerging plants and 21% of the plants in the seedling stage. Seventy per cent of all uprooted plants were completely covered by soil. An increase in working depth from 10 mm to 30 mm doubled the average fraction of uprooted plants. Uprooting was also promoted by higher soil moisture contents and higher working speeds. Average uprooting selectivity (=fraction of uprooted emerging plants/fraction of uprooted seedlings of the same species) varied between 2.0 (deep tillage and high speed) and 5.6 (dry soil). If tines could keep a distance of more than 3 mm from the crop and weed plants, the average selectivity of all treatments would improve from 2.4 to 5.5 and the average fraction of uprooted seedlings would decrease from 21% to 8%. This study indicates that uprooting may be a more important weed control mechanism than commonly believed. If working depth and the path of the harrow tines in relation to crop rows could be accurately controlled, uprooting could be a relatively selective weed control mechanism at early crop growth stages.     

Lectin histochemical pattern on the normal and cystic ovaries of sows

The lectin histochemical pattern (LHP) was characterized and compared in normal and cystic ovaries of sows. Six biotinylated lectins (PNA, SBA, WGA, RCA‐1, DBA and UEA‐1) were used on tissue sections. In the normal ovaries, the reaction to UEA‐1 and SBA was mild to moderate in mesothelial and endothelial cells. RCA‐1 staining was mild to moderate in theca interna of growing follicles, corpora luteum and mesothelium. In addition, this lectin presented strong reaction in endothelial cells, granulosa cells of atretic follicles, zona pellucida of growing follicles and plasma. DBA showed strong intensity in mesothelial and endothelial cells. There was mild to moderate reactivity to WGA in granulosa cells, corpus luteum and theca interna of follicles in development, and moderate in zona pellucida, in granulosa cells of atretic follicles and mesothelium. PNA staining was mild to moderate in oocytes and in the adventitia and media of medullary arteries. Changes in the LHP of the cystic ovaries were noted; however, there were no differences in these findings between the follicular and luteinized cysts. UEA‐1 reactivity in the cystic ovaries was moderately reduced in the mesothelial and endothelial cells, whereas there was mild reduction in the DBA staining in the granulosa cells. Reaction to RCA‐1 and WGA in the cysts also was decreased in theca interna, zona pellucida and granulosa cells of atretic follicles. Furthermore, endothelium and theca interna in the cystic ovaries presented mild reduction of marcation to SBA, whereas there was decreased reactivity to PNA in the oocytes and adventitia and media layers of the medullary arteries. The results of the current study show that cysts modify the LHP in swine ovaries. These changes of glycoconjugates in many ovarian structures could modify diverse process and may be one of the reasons for decreased fertility in sows.     

The selective soil covering mechanism of weed harrows on sandy soil

Improvement of intra-row mechanical weed control is important to reduce the reliance on herbicides in arable crops and vegetables. Covering weeds by soil is an important weed control mechanism of weed harrows. A shallow post-emergence harrow cultivation controls weeds but also damages the crop to some extent. This paper explores how plants get covered by soil and how a plant’s resistance against being covered is related to its height, flexibility and shape of leaves. Seedlings of two contrasting species were sown in bins filled with a sandy soil and harrowed by a small model harrow in the laboratory. Covering selectivity (percentage covered ryegrass/percentage covered garden cress) could be influenced by soil moisture content, working depth and working speed. Differences in covering were related to spatial patterns of plant downward bending and soil surface level upheaval. These patterns are associated with soil failure patterns near tines and soil flow patterns, connected with different effects of plant height and plant flexibility. This study indicates that relationships between weed control and crop covering may not only depend on weed and crop characteristics but also on soil conditions and implement settings. As less than 10% of the covered plants were buried deeper than 15 mm, covering would mainly cause growth reduction and little killing. Limited burial depth may be an important cause for limited weed control effectiveness of harrowing.