Improved fallows come of age in the tropics

Improved fallows are the deliberate planting of fast-growing species — usually legumes — for rapid replenishment of soil fertility. Improved fallows are rapidly spreading in several regions of the tropics as a sensible way for in situ accumulation of large quantities of N in vegetation and soil, as well as for providing sustainability enhancing services. Research on improved fallows increased after the mid 1980s with the development of what is known as the second soil fertility paradigm, which is based on sustainability considerations. Many lessons have emerged from short-term improved fallows (<5 years duration). These include the diversity of farm sizes where improved fallows are used, the advantage of sequential versus simultaneous systems, the utilization of dry seasons unfavorable for crop production, the comparative advantages of woody versus herbaceous leguminous fallows, the magnitude of N accumulation, the strategic use of N fertilizers, and the importance of P. Other key services provided by fallows include fuelwood production, recycling of nutrients besides N, provision of a C supply to soil microorganisms, weed suppression, Striga control, and improved soil water storage. Natural fallows of non-legume shrubs belonging to the Asteraceae family, collectively called daisy fallows, may provide lessons for the development of improved fallows. The maintenance of genetic diversity in fallows is paramount. The main limiting factor in Africa is clearly the supply of germplasm of improved fallow species. This must be overcome though large-scale seed orchards and nursery development before impact at the scale of millions of farmers can take place.This revised version was published online in November 2005 with corrections to the Cover Date.     

全肠外营养脂肪乳剂脂肪酸形态对仔猪不同组织中脂肪酸组成的影响

目前,人类婴儿低初生重的总肠外营养（TPN）研究表明脂肪乳剂对于新生儿的营养是合适的,但不是最佳的选择。人类和猪的脂肪酸代谢非常相似,目前的研究主要集中在脂肪乳剂如何在TPN的临床作用。不同组成脂肪酸对新生仔猪进行7d处理,对于靠母乳替代物的仔猪而言,对组织脂肪酸的组成存在影响。在脂肪乳中,不同比例脂肪酸或母乳替代物对应的血浆,骨骼肌、皮下脂肪、肝脏、心脏,胰腺,胃及小肠的总血脂或脑磷脂呈正态的线性关系,而后者相关性最低。除大脑外,组织中的油酸或α-亚麻酸的比例与对应的脂肪乳或者母乳替代物相关,而亚麻酸的比例与研完的组织密切相关。除脑磷脂外,omegaven组中仔猪组织的二十碳五烯酸和二十二碳六烯酸含量更高。结论除大脑外,血浆脂肪酸组成以及仔猪不同组织受全肠外营养乳剂中不饱和脂肪酸形态的影响极大。然而,脑磷脂脂肪酸的组成受日粮组成的影响要小,表明在生长的关键阶段有效的代谢是确保脂肪酸组成的关键。     

Experimental realization of a magnetic cloak

Invisibility to electromagnetic fields has become an exciting theoretical possibility. However, the experimental realization of electromagnetic cloaks has only been achieved starting from simplified approaches (for instance, based on ray approximation, canceling only some terms of the scattering fields, or hiding a bulge in a plane instead of an object in free space). Here, we demonstrate, directly from Maxwell equations, that a specially designed cylindrical superconductor-ferromagnetic bilayer can exactly cloak uniform static magnetic fields, and we experimentally confirmed this effect in an actual setup.     

Determination of cardiac output in neonatal foals by ultrasound velocity dilution and its comparison to the lithium dilution method

Objective – To compare cardiac output (CO) measured by use of lithium dilution (LiDCO) and ultrasound velocity dilution (UDCO) in conditions of high, intermediate, and low CO in anesthetized foals.
Design – Original prospective study.
Setting – University teaching hospital.
Animals – Six foals 1–3 days of age (38–45 kg).
Interventions – Neonatal foals were anesthetized and instrumented to measure direct blood pressure, heart rate, arterial blood gases, and CO. The CO was measured by use of LiDCO and UDCO techniques. Measurements were obtained from each foal at baseline and during low, intermediate, and high CO states. Measurements were converted to cardiac index (cardiac index=CO/body weight) values for statistical analysis. Agreement between the 2 methods was determined using Bland and Altman analysis and concordance correlation coefficients.
Measurements and Main Results – LiDCO determinations of CO ranged between 4.0 and 14.0 L/min resulting in cardiac index ranging between 75.5 and 310 mL/kg/min. There was no significant effect of blood pressure variation on bias or relative bias ( P =0.62 and 0.93, respectively). The mean bias and relative bias of UDCO (±SD) compared with LiDCO were −20.1±39.2 mL/kg/min and −7.7±23.4%, respectively. Concordance correlation coefficient between LiDCO and UDCO was 0.833.
Conclusions – When compared with LiDCO, the UDCO technique has acceptable clinical utility for measuring CO in healthy anesthetized newborn foals.     

Effect of detomidine on visceral and somatic nociception and duodenal motility in conscious adult horses

ObjectiveTo evaluate the effects of detomidine on visceral and somatic nociception, heart and respiratory rates, sedation, and duodenal motility and to correlate these effects with serum detomidine concentrations.Study designNonrandomized, experimental trial.AnimalsFive adult horses, each with a permanent gastric cannula weighing 534 ± 46 kg.MethodsVisceral nociception was evaluated by colorectal (CRD) and duodenal distension (DD). The duodenal balloon was used to assess motility. Somatic nociception was assessed via thermal threshold (TT). Nose–to–ground (NTG) height was used as a measure of sedation. Serum was collected for pharmacokinetic analysis. Detomidine (10 or 20 μg kg^?1) was administered intravenously. Data were analyzed by means of a three–factor anova with fixed factors of treatment and time and random factor of horse. When a significant time × treatment interaction was detected, differences were compared with a simple t–test or Bonferroni t–test. Significance was set at p < 0.05.ResultsDetomidine produced a significant, dose–dependent decrease in NTG height, heart rate, and skin temperature and a significant, nondose–dependent decrease in respiratory rate. Colorectal distension threshold was significantly increased with 10 μg kg^?1 for 15 minutes and for at least 165 minutes with 20 μg kg^?1. Duodenal distension threshold was significantly increased at 15 minutes for the 20 μg kg^?1 dose. A significant change in TT was not observed at either dose. A marked, immediate decrease in amplitude of duodenal contractions followed detomidine administration at both doses for 50 minutes.Conclusions and clinical relevanceDetomidine caused a longer period of visceral anti–nociception as determined by CRD but a shorter period of anti–nociception as determined by DD than has been previously reported. The lack of somatic anti–nociception as determined by TT testing may be related to the marked decrease in skin temperature, likely caused by peripheral vasoconstriction and the low temperature cut–off of the testing device.     

Musculoskeletal injuries in Standardbred racehorses on Prince Edward Island

A study of musculoskeletal injuries in Standardbred racehorses on Prince Edward Island was conducted to determine the incidence and risk factors for injury. Monthly information was collected from 10 trainers and 153 Standardbred horses over a 12-month period. Seventeen new injuries were identified in pacers, representing a horse level incidence risk of 23% and an incidence rate of injury of 2.19 per horse-month at risk. Forty-one percent of the injuries occurred during a race, 53% during training and 6% during jogging. Fourteen horses had experienced a previous injury and 3 of these horses experienced a new injury during the study period. Potential risk factors for injury were the speed at which the horse was trained, previous injury, and the conformational fault of offset knees.     

Method development and application to determine potential plant uptake of antibiotics and other drugs in irrigated crop production systems

Studies have shown the detection of emerging contaminants (ECs), of which pharmaceuticals are a subset, in surface waters across the United States. The objective of this study was to develop methods, and apply them, to evaluate the potential for food chain transfer when EC-containing waters are used for crop irrigation. Greenhouse experiments were performed in which select food crops were irrigated with water spiked with three antibiotics. Field experiments, at two different sites, were conducted. Select crops were irrigated with wastewater effluent known to contain ECs, EC-free well water, and Colorado River water containing trace-level ECs. The results of the greenhouse studies show the potential for uptake of one or more of the antibiotics evaluated, albeit at very low levels. In those food crops watered with wastewater effluent, only an industrial flavoring agent, N,N'-dimethylphenethylamine (DMPEA), was consistently found. None of the evaluated contaminants were found in crops irrigated with Colorado River water.     

Bioequivalence of ivermectin formulations in pigs and cattle

The vehicle in which endectocide compounds are formulated plays a relevant role in their absorption kinetics and resultant systemic availability. The pharmaceutical bioequivalence and comparative plasma disposition kinetics of ivermectin (IVM), following the subcutaneous administration of two injectable formulations to pigs and cattle were investigated using parallel experimental designs. Sixteen parasite-free male Duroc Jersey-Yorkshire crossbred pigs (90-110 kg) (Expt 1) and 16 parasite-free male Holstein calves (100-120 kg) (Expt 2) were divided into two groups and treated subcutaneously at either 300 (pigs) or 200 (calves) microg/kg with two different propylene glycol/glycerol formal (60: 40) based IVM formulations; in both experiments pigs or calves in Group A received the test (IVM-TEST) formulation and those in Group B were treated with the reference formulation (IVM-CONTROL). Heparinized blood samples were taken from 0 h up to either 20 (pigs) or 30 (calves) days post-treatment and plasma was extracted, derivatized and analysed by high performance liquid chromatography (HPLC) using fluorescence detection. Early detection of IVM (12 h) with a peak plasma concentration (C(max)) between 33 and 39 ng/mL was observed in pigs. The drug was detected in plasma up to 20 days post-administration of either formulation, resulting in elimination half-lives between 3.47 and 3.80 days. There were no differences between the IVM-TEST and IVM-CONTROL formulations in the kinetic parameters (except t(max)) obtained in pigs. IVM was detected in plasma between 12 h and 30 days post-administration of both formulations under investigation in cattle. The plasma disposition kinetics of IVM in calves was similar following treatment with both formulations. C(max) values (between 40.5 and 46.4 ng/mL) were achieved at 2 days post-administration of both formulations. None of the estimated kinetic parameters were statistically different between drug formulations. The injectable IVM formulations investigated were bioequivalent after their subcutaneous administration to both pigs and calves at recommended dose rates.     

Nonisotopic detection of Loma salmonae (microspora) in rainbow trout (Oncorhynchus mykiss) gills by in situ hybridization

Loma salmonae, a microsporidian parasite of salmonids of the genus Oncorhynchus, is a significant cause of economic loss in pen-reared chinook salmon (O. tschawytscha). Final stages of L. salmonae infections are easily recognized by the xenomas that form in the gills during sporogony. However, early prexenoma stages of infection (3 weeks or less after infection) are difficult to detect on histologic slides. An L. salmonae-specific single-stranded DNA probe labeled with digoxigenin was used to detect these prexenoma stages of L salmonae by in situ hybridization in experimentally infected rainbow trout. This method allows detection of the parasite in the gills only 2 weeks after infection, providing a sensitive and specific way of detecting L. salmonae during the early stages of infection.