短期休牧对克氏针茅草原植物群落物种多样性及稳定性影响研究

文章采用野外植物样方采取及实验室数据分析相结合的方法,以阿巴嘎旗北部牧户常年放牧和隔年休牧的冬季草场为例,探讨短期休牧对克氏针茅草原植物物种多样性及群落稳定性的影响。结论如下:(1)两个草场植物群落内植物数量差异不大,主要差异表现在主要植物的平均重要值及两个草场仅有2对共优种。此外,短期休牧冬季草场的禾本科植物比重提升的同时,一年生藜科植物也显著提升;(2)短期休牧冬季草场的植物群落物种多样性指数略高于常年放牧冬季草场,但差异不显著;(3)两个草场植物群落处于中等相似水平,植物种间存在分异化趋势;(4)短期休牧冬季草场植物群落总体呈微弱正联结,种间联结松散,处于正向演替阶段,常年放牧冬季草场呈微弱负相关,群落较不稳定,存在一定退化风险;(5)两个草场的植物群落离稳定性都有一定差距,但短期休牧冬季草场植物群落稳定性略好于常年放牧冬季草场。可见,短期休牧有利于克氏针茅草原植物群落物种多样性和稳定性保持。     

Tracking the long-term decline and recovery of an isolated population

Effects of small population size and reduced genetic variation on the viability of wild animal populations remain controversial. During a 35-year study of a remnant population of greater prairie chickens, population size decreased from 2000 individuals in 1962 to fewer than 50 by 1994. Concurrently, both fitness, as measured by fertility and hatching rates of eggs, and genetic diversity declined significantly. Conservation measures initiated in 1992 with translocations of birds from large, genetically diverse populations restored egg viability. Thus, sufficient genetic resources appear to be critical for maintaining populations of greater prairie chickens.     

Lactobacillus rhamnosus strain GG is a potential probiotic for calves

Diarrhea is a common occurrence in neonatal calves. Several veterinary probiotics claiming to prevent or treat calf diarrhea are available, but have not been well studied. This study assessed the capability of Lactobacillus rhamnosus strain GG (LGG) to maintain viability in the gastrointestinal tract of calves. We also determined whether LGG can be administered in an oral rehydration solution (ORS) without compromising the efficacy of the ORS or the viability of LGG, and whether LGG produces D-lactate or not. To investigate the intestinal survival of LGG, 15 calves were randomized into 3 groups and LGG was administered orally with their morning milk feeding on 3 consecutive days at a low (LD), medium (MD), or high (HD) dosage. Fecal samples were collected on days 0 (control), 1, 2, 3, 5, and 7 and incubated for 72 h on deMan, Rogosa, Sharpe agar. Twenty-four hours after the 1st feeding, LGG was recovered from 1 out of 5 calves in the LD group, 4 out of 5 calves in the MD group, and 5 out of 5 calves in the HD group. To determine if LGG caused the glucose levels in the ORS to drop below effective levels, 1.5 L of the ORS was incubated with LGG for 2 h at 37 degrees C and the glucose concentration was measured every 20 min using a glucose meter. This ORS was then further incubated for 10 h and aliquots analyzed by high performance liquid chromatography to determine if D-lactate was produced by LGG. Glucose concentrations did not change over the 2 h of incubation, and no D-lactate was produced after 48 h. The LGG maintained viability in ORS. Therefore, this study demonstrated that LGG survives intestinal transit in the young calf, produces no D-lactate, and can be administered in an ORS.     

The Control of Reactive Oxygen Species Influences Porcine Oocyte In Vitro Maturation

The aim of this study was to examine the effect of varying intracellular reactive oxygen species (ROS) levels during oocyte in vitro maturation with enzymatic ROS production systems (xanthine + xanthine oxidase or xanthine + xanthine oxidase + catalase), scavenger systems (catalase or superoxide dismutase + catalase) or cysteine on porcine oocyte maturation. Oocyte ROS levels showed an increase when H₂O₂ or O₂?^‐ production systems were added to the culture medium (p < 0.05). On the other hand, the presence of ROS scavengers in the maturation medium did not modify oocyte ROS levels compared with the control after 48 h of maturation, but the addition of cysteine induced a decrease in oocyte ROS levels (p < 0.05). The ROS production systems used in this work did not modified the percentage of oocyte nuclear maturation, but increased the decondensation of sperm head (p < 0.05) and decreased the pronuclear formation (p < 0.05). In turn, the addition of O₂?^‐ and H₂O₂ scavenging systems during in vitro maturation did not modify the percentage of oocytes reaching metaphase II nor the oocytes with decondensed sperm head or pronuclei after fertilization. However, both parameters increased in the presence of cysteine (p < 0.05). The exogenous generation of O₂?^‐ and H₂O₂ during oocyte in vitro maturation would not affect nuclear maturation or later sperm penetration, but most of the spermatozoa cannot progress to form the pronuclei after fusion with the oocyte. The decrease in endogenous ROS levels by the addition of cysteine would improve pronuclear formation after sperm penetration.     

Mycoplasma bovis and otitis in dairy calves in the United Kingdom

Signs of severe otitis media in 20% of dairy calves on one farm were associated with Mycoplasma bovis infection, based on isolation from the external ear canal and nares. Affected calves seroconverted to M. bovis and no other significant bacteria were isolated. Infection was considered likely to have originated from cows in the milking herd based on evidence of seroconversion and detection of infection in a milk sample. M. bovis infection should be considered when investigating otitis problems in calves.     

“Some are more fair than others”: fair trade certification,development, and North–South subjects

At the same time as fair trade certified products are capturing an increasing market share, a growing number of scholars and practitioners are raising serious questions about who benefits from certification. Through a critique of north–south narratives, this paper draws on contemporary themes in fair trade scholarship to draw out different ways of thinking about fair trade outside of the dichotomous north–south framing. I argue that, through the creation of fair trade subjects of the “global north” and “global south,” certification has normalized and naturalized dichotomous power relations. The primary concern of this paper is to demonstrate the problems with situating certification and scholarship in the north–south binary and to push examination toward a more nuanced analysis of how certification and development are shaped in-place. This intervention is important for assisting with stepping away from long-standing debates regarding the effectiveness of certification, and additionally in contributing to critical thinking on economic development more broadly.     

基于EDA技术的自动立木整枝机无线遥控接收系统

在分析自动立木整枝机工作过程和控制要求的基础上,该文详细阐述了自动立木整枝机无线遥控接收系统的组成及工作原理,进而采用电子设计自动化(EDA)技术设计了自动立木整枝机无线遥控接收系统的数字控制逻辑.通过优化CPLD内部逻辑电路,有效消除了逻辑竞争冒险.仿真结果表明,该系统控制可靠性较高,能有效提高自动立木整枝机的功能安全性.      

The treatment of diarrhoea in the adult horse

The priority in treating the equine patient with acute diarrhoea is to stabilise the haemodynamic aberrations secondary to the fluid and electrolyte losses. Once this has been initiated and the patient is stabilised ancillary treatments may be beneficial. Besides the well established effects of NSAIDs and polymixin B on systemic inflammation, recent studies suggest that the use of DTOS to bind bacterial toxins and Saccharomyces boulardii to reduce the severity and duration of diarrhoea may be beneficial. The justification for using probiotic products is scant. There is no evidence to suggest that systemic use of antimicrobials benefits equine patients with colitis, with the exception of metronidazole in cases of clostridial diarrhoea. In light of their potentially detrimental effects, their use can, in the opinion of the authors, not be advocated. Better understanding of the pathways of systemic inflammation and more selective anti‐inflammatory drugs may be of great benefit in the future.