Exchangeable potassium and potassium balances in organic crop rotations on a coarse sand   总被引：3，自引：0，他引：3  

M. Askegaard  J. Eriksen  J.E. Olesen 《Soil Use and Management》2003,19(2):96-103

Abstract. Crops on sandy soils (<5% clay) are exposed to K deficiency due to the small release and high leaching losses of K. Reliable tools are needed to improve the K management in cropping systems with limited K input, such as organic farming where import of nutrients are restricted according to the EC regulations. We investigated K balances and exchangeable K (K_exch) changes in an organic crop rotation experiment. Potassium leaching decreased from 42 kg ha⁻¹ in 1998/99 to 21 kg ha⁻¹ in 2000/01 as an average of a crop rotation (spring barley, grass-clover, winter wheat and pea/barley) with manure application and without catch crops. In the same period, spring K_exch decreased from 5.0 to 3.0 mg K 100 g soil⁻¹ (0–20 cm). The retention of the straw K left in the field after harvest increased with decreasing levels of K_exch. The cereal crops did not respond to K application but in the pea/barley mixture the pea yield increased by 46%. The concordance between measured K balances and changes in K_exch was weak. Exchangeable K is suitable as a tool for K management on a rotational basis, and a K_exch above 3 mg 100 g soil⁻¹ in the autumn should be avoided to minimize K leaching.  相似文献   

C and N turnover in structurally intact soils of different texture     

Ingrid K Thomsen  Per SchjønningJørgen E Olesen  Bent T Christensen 《Soil biology & biochemistry》2003,35(6):765-774

The turnover of native and applied C and N in undisturbed soil samples of different texture but similar mineralogical composition, origin and cropping history was evaluated at −10 kPa water potential. Cores of structurally intact soil with 108, 224 and 337 g clay kg⁻¹ were horizontially sliced and ¹⁵N-labelled sheep faeces was placed between the two halves of the intact core. The cores together with unamended treatments were incubated in the dark at 20 °C and the evolution of CO₂-C determined continuously for 177 d. Inorganic and microbial biomass N and ¹⁵N were determined periodically. Net nitrification was less in soil amended with faeces compared with unamended soil. When adjusted for the NO₃-N present in soil before faeces was applied, net nitrification became negative indicating that NO₃-N had been immobilized or denitrified. The soil most rich in clay nitrified least N and ¹⁵N. The amounts of N retained in the microbial biomass in unamended soils increased with clay content. A maximum of 13% of the faeces ¹⁵N was recovered in the microbial biomass in the amended soils. CO₂-C evolution increased with clay content in amended and unamended soils. CO₂-C evolution from the most sandy soil was reduced due to a low content of potentially mineralizable native soil C whereas the rate constant of C mineralization rate peaked in this soil. When the pool of potentially mineralizable native soil C was assumed proportional to volumetric water content, the three soils contained similar proportions of potentially mineralizable native soil C but the rate constant of C mineralization remained highest in the soil with least clay. Thus although a similar availability of water in the three soils was ensured by their identical matric potential, the actual volume of water seemed to determine the proportion of total C that was potentially mineralizable. The proportion of mineralizable C in the faeces was similar in the three soils (70% of total C), again with a higher rate constant of C mineralization in the soil with least clay. It is hypothesized that the pool of potentially mineralizable C and C rate constants fluctuate with the soil water content.  相似文献   

Outbreak of viral haemorrhagic septicaemia (VHS) in lumpfish (Cyclopterus lumpus) in Iceland caused by VHS virus genotype IV     

Sigríur Gumundsdttir  Niccol Vendramin  Argelia Cuenca  Heia Sigurardttir  Arni Kristmundsson  Tine Moesgaard Iburg  Niels Jrgen Olesen 《Journal of fish diseases》2019,42(1):47-62

A novel viral haemorrhagic septicaemia virus (VHSV) of genotype IV was isolated from wild lumpfish (Cyclopterus lumpus), brought to a land‐based farm in Iceland, to serve as broodfish. Two groups of lumpfish juveniles, kept in tanks in the same facility, got infected. The virus isolated was identified as VHSV by ELISA and real‐time RT‐PCR. Phylogenetic analysis, based on the glycoprotein (G) gene sequences, may indicate a novel subgroup of VHSV genotype IV. In controlled laboratory exposure studies with this new isolate, there was 3% survival in the I.P. injection challenged group while there was 90% survival in the immersion group. VHSV was not re‐isolated from fish challenged by immersion. In a cohabitation trial, lumpfish infected I.P. (shedders) were placed in tanks with naïve lumpfish as well as naïve Atlantic salmon (Salmo salar L.). 10% of the lumpfish shedders and 43%–50% of the cohabiting lumpfish survived after 4 weeks. 80%–92% of the Atlantic salmon survived, but no viral RNA was detected by real‐time RT‐PCR nor VHSV was isolated from Atlantic salmon. This is the first isolation of a notifiable virus in Iceland and the first report of VHSV of genotype IV in European waters.  相似文献   

Effects of earthworms on bulk density: A meta‐analysis     

Birgit Lang  David J. Russell 《European Journal of Soil Science》2020,71(1):80-83

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Specific polyphenol oxidase activity of red clover (Trifolium pratense) and its relation with forage quality in field experiments     

Birgit Eickler  Jana Kleen  F. Taube 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(1):39-49

Abstract

In feeding studies, red clover (RC) influenced positively the N utilization by ruminants. A relationship between polyphenol oxidase (PPO) activity and forage quality has not been established. Our objective was to investigate seasonal, site, genotype, and management effects on specific PPO activity in RC in three experiments under field conditions, and relate the activity to forage-quality parameters. In Experiment 1, six RC genotypes at two study sites were submitted to a 3-cut system. Specific PPO activity, forage quality, and vegetation stage were determined. PPO activity varied between harvest and study sites, with genotypes differing up to 3-fold in PPO activity within harvests. The specific PPO activity, forage quality, and vegetation stage in RC subjected to 5-cut system and grazing (Experiment 2) were determined. Additionally, in Experiment 3, cutting frequency in RC swards including mechanical stress (rolling) was investigated. The induction of PPO activity in RC by grazing or mechanical stress (Experiments 2 and 3) increased the activity up to 2.5-fold compared with RC at similar vegetation stage submitted to the 5-cut system. Mechanical stress induced by grazing or rolling, and seasonal differences, seem to have a larger influence on specific PPO activity than does the genotype effect observed in Experiment 1. For forage quality, an increased specific PPO activity explained 29–46% of the reduction in protein fraction ‘A’ content (non-protein N) in the cutting systems in Experiments 2 and 3. Other CP fractions achieved a lower relation. Furthermore, the precipitation-to-temperature ratio preceeding a harvest explained 63% of the variation in the specific PPO activity. In conclusion, the PPO activity in RC is induced by grazing and rolling. Whereas weather conditions preceeding a harvest showed a large influence, genotype influence had only minor relevance. These results may have implications for regional harvest management towards efficient N utilization by ruminants.  相似文献   

Diagnosis of Taxus (yew) poisoning in a horse.     

Asheesh K Tiwary  Birgit Puschner  Hailu Kinde  Elizabeth R Tor 《Journal of veterinary diagnostic investigation》2005,17(3):252-255

A 2-year-old bay Thoroughbred colt was found dead overnight in its stall without a known history of any illness, existing disease, or toxicant exposure. No information on the clinical signs before this animal's death was reported. A full necropsy was performed the next morning and revealed a mild to moderate degree of endocardial hemorrhages in both ventricles. Microscopic examination of the heart showed an acute mild multifocal necrosis of papillary muscles and ventricles. The stomach content contained approximately 2% Taxus alkaloids as determined by gas chromatography/mass spectrometry. In the past, diagnosis of Taxus poisoning has been mainly based on history of exposure and the presence of plant parts in the gastrointestinal tract. Pathological lesions associated with Taxus poisoning have not been published for horses. Therefore, this is the first report of cardiac lesions in a horse after lethal exposure to Taxus. On the basis of these findings, it is suggested that Taxus exposure needs to be considered in the differential diagnosis of horses that die suddenly or have cardiac lesions suggestive of Taxus exposure, even if intact plant parts are not identified in the stomach by the naked eye.  相似文献   

Efficacy of milbemycin oxime in the treatment of canine generalized demodicosis: a retrospective study of 99 dogs (1995-2000)     

Holm BR 《Veterinary dermatology》2003,14(4):189-195

Ninety-nine dogs diagnosed with generalized demodicosis were treated with milbemycin oxime. Cases diagnosed before two years of age were classified as juvenile-onset (53%) and those diagnosed after two years of age as adult-onset (47%). Dogs were considered cleared of mites when none could be demonstrated in scrapings and cured if no relapse was seen for 12 months. Eighty-five per cent (84/99) were cured with milbemycin oxime used for 1-6 months (mean 2.3 months) at a dosage of 0.5-1.6 mg kg-1 body weight (mean 0.75 mg kg-1). No significant difference in dosage or treatment time was seen between juvenile and adult cases. Chance of cure was significantly better in young animals (cured cases mean age 2.97 years) than in older animals (not cured cases mean age 8.02 years). Start of treatment early in the course of disease gave a significantly better chance of cure. Cases with severe pododemodicosis had less chance of a cure (9/11 not cured).  相似文献   

Assessment of melamine and cyanuric acid toxicity in cats.   总被引：30，自引：0，他引：30  

Birgit Puschner  Robert H Poppenga  Linda J Lowenstine  Michael S Filigenzi  Patricia A Pesavento 《Journal of veterinary diagnostic investigation》2007,19(6):616-624

The major pet food recall associated with acute renal failure in dogs and cats focused initially on melamine as the suspect toxicant. In the course of the investigation, cyanuric acid was identified in addition to melamine in the offending food. The purpose of this study was to characterize the toxicity potential of melamine, cyanuric acid, and a combination of melamine and cyanuric acid in cats. In this pilot study, melamine was added to the diet of 2 cats at 0.5% and 1%, respectively. Cyanuric acid was added to the diet of 1 cat at increasing doses of 0.2%, 0.5%, and 1% over the course of 10 days. Melamine and cyanuric acid were administered together at 0%, 0.2%, 0.5%, and 1% to 1 cat per dose group. No effect on renal function was observed in cats fed with melamine or cyanuric acid alone. Cats dosed with a combination were euthanized at 48 hours after dosing because of acute renal failure. Urine and touch impressions of kidneys from all cats dosed with the combination revealed the presence of fan-shaped, birefringent crystals. Histopathologic findings were limited to the kidneys and included crystals primarily within tubules of the distal nephron, severe renal interstitial edema, and hemorrhage at the corticomedullary junction. The kidneys contained estimated melamine concentrations of 496 to 734 mg/kg wet weight and estimated cyanuric acid concentrations of 487 to 690 mg/kg wet weight. The results demonstrate that the combination of melamine and cyanuric acid is responsible for acute renal failure in cats.  相似文献   

Changes in compact bone microstructure of rats subchronically exposed to cadmium     

Hana Duranova  Monika Martiniakova  Radoslav Omelka  Birgit Grosskopf  Ivana Bobonova  Robert Toman 《Acta veterinaria Scandinavica》2014,56(1)

Background

Chronic exposure to cadmium (Cd), even at low concentrations, has an adverse impact on the skeletal system. Histologically, primary and secondary osteons as basic structural elements of compact bone can also be affected by several toxicants leading to changes in bone vascularization and mechanical properties of the bone. The current study was designed to investigate the effect of subchronic peroral exposure to Cd on femoral bone structure including histomorphometry of the osteons in adult male rats.In our study, 20 one-month-old male Wistar rats were randomly divided into two experimental groups. In the first group, young males received a drinking water containing 30 mg of CdCl₂/L, for 90 days. Ten one-month-old males without Cd intoxication served as a control group. After 90 days of daily peroral exposure, body weight, femoral weight, femoral length, cortical bone thickness and histological structure of the femora were analysed.

Results

We found that subchronic peroral application of Cd had no significant effect on body weight, femoral length and cortical bone thickness in adult rats. On the other hand, femoral weight was significantly increased (P < 0.05) in Cd-intoxicated rats. These rats also displayed different microstructure in the middle part of the compact bone where vascular canals expanded into central area of substantia compacta and supplied primary and secondary osteons. Additionally, a few resorption lacunae which are connected with an early stage of osteoporosis were identified in these individuals. Histomorphometrical evaluations showed that all variables (area, perimeter, maximum and minimum diameter) of the primary osteons’ vascular canals, Haversian canals and secondary osteons were significantly decreased (P < 0.05) in the Cd group rats. This fact points to alterations in bone vascularization.

Conclusions

Subchronic peroral exposure to Cd significantly influences femoral weight and histological structure of compact bone in adult male rats. It induces an early stage of osteoporosis and causes reduced bone vascularization. Histomorphometrical changes of primary and secondary osteons allow for the conclusion that the bone mechanical properties could be weakened in the Cd group rats. The current study significantly expands the knowledge on damaging action of Cd on the bone.  相似文献   

Pain in pigs: How much does it hurt?     

Claudia Spadavecchia  Birgit Ranheim 《Veterinary journal (London, England : 1997)》2014,199(3):317-318

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