Soluble organic nitrogen in agricultural soils   总被引：36，自引：0，他引：36  

D. V. Murphy  A. J. Macdonald  E. A. Stockdale  K. W. T. Goulding  S. Fortune  J. L. Gaunt  P. R. Poulton  J. A. Wakefield  C. P. Webster  W. S. Wilmer 《Biology and Fertility of Soils》2000,30(5-6):374-387

 The existence of soluble organic forms of N in rain and drainage waters has been known for many years, but these have not been generally regarded as significant pools of N in agricultural soils. We review the size and function of both soluble organic N extracted from soils (SON) and dissolved organic N present in soil solution and drainage waters (DON) in arable agricultural soils. SON is of the same order of magnitude as mineral N and of equal size in many cases; 20–30 kg SON-N ha^–1 is present in a wide range of arable agricultural soils from England. Its dynamics are affected by mineralisation, immobilisation, leaching and plant uptake in the same way as those of mineral N, but its pool size is more constant than that of mineral N. DON can be sampled from soil solution using suction cups and collected in drainage waters. Significant amounts of DON are leached, but this comprises only about one-tenth of the SON extracted from the same soil. Leached DON may take with it nutrients, chelated or complexed metals and pesticides. SON/DON is clearly an important pool in N transformations and plant uptake, but there are still many gaps in our understanding. Received: 10 June 1999  相似文献   

Pronuclear Embryo Yield in Canindé and Saanen Goats for DNA Microinjection     

RR Moura  ES Lopes‐Junior  DIA Teixeira  IA Serova  LE Andreeva  LM Melo  VJF Freitas 《Reproduction in domestic animals》2010,45(5):e101-e106

The objective of this study was to examine the effect of donor breed on pronuclear‐stage embryo yield to be used for DNA microinjection in a transgenesis goat program. Twelve Canindé and twelve Saanen goats were heat synchronized using a progestagen‐cloprostenol treatment. Forty‐eight hours before the sponge removal, superovulation was induced with a total administration of 4.4 mg/kg bodyweight NIH‐FSH‐P1, given twice daily in decreasing doses over 3 days. In addition, goats received 100 μg of GnRH and they were hand‐mated at 36 and 48 h after progestagen removal. Embryo recovery was performed by oviduct flushing at 72 h after sponge removal. Embryos were microinjected with a DNA construct and noticeable swelling of the nuclei was the criterion for successful microinjection. The total diameter, cytoplasm diameter, zona pellucida thickness and pronuclei diameter were measured for each microinjected embryo. A higher (p < 0.05) percentage of fertilized ova was observed in Canindé (89.9%) than Saanen (36.2%) goats. In addition, Canindé donors produced a higher percentage of pronuclear embryos when compared with Saanen: 72.5% vs 20.6% (p < 0.05), respectively. Successful microinjection was verified in 96.7% and 73.3% of times in Canindé and Saanen embryos, respectively (p < 0.05). Significant differences were observed for all morphometric parameters except for cytoplasm diameter. In conclusion, under our study experimental conditions, Canindé were more efficient than Saanen goats concerning the pronuclear embryo yield and manipulation. The use of Canindé goats in transgenesis programs could be increase the interest in their breeding and could be contribute to saving them from extinction.  相似文献   

Seed dormancy and germination in the summer annual Galeopsis speciosa     

LM KARLSSON  JAL ERICSSON  & P MILBERG 《Weed Research》2006,46(5):353-361

This study examined germination and dormancy in Galeopsis speciosa (Lamiaceae), a common summer annual weed in cold‐temperate areas. Seeds collected in southern Sweden were subjected to several experiments. The seeds were dormant at maturity. Seeds sown outdoors after collection produced a small number of seedlings that emerged early in the spring. After long cold stratification or stratification outdoors over two winters, the maximum germination was 40–50%; germination occurring over a wide range of temperatures. Warm stratification preceding cold stratification had no effect on germination, but repeated warm and cold periods seemed to promote germination. Gibberellic acid (GA) stimulated germination, but full germination was only achieved after more than 2 months of incubation at the most suitable temperature regime tested. Excised embryos grew and developed into normal seedlings. With these results, the species does not fit into the currently used system for seed dormancy classifications. The response to GA and the growth of excised embryos indicate non‐deep or intermediate physiological dormancy, but dormancy alleviation by stratification was not in line with the guiding principles for these classifications. Galeopsis speciosa has a strong dormancy that is sufficiently alleviated during the winter to allow germination of only part of a seed batch each year; hence a stepwise germination pattern occurs over a period of several years.  相似文献   

The Equine Manual     

LM Begg 《Australian veterinary journal》2006,84(8):300-300

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LIPOMA AS A CAUSE OF INTESTINAL STRANGULATION     

J. Wakefield  Rainey M.R.C.V.S. 《Australian veterinary journal》1942,18(3):133-133

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An In Vitro Investigation into the Effects of a Marine-Derived,Multimineral Supplement in Simulated Equine Stomach and Hindgut Environments     

Meriel Moore-Colyer  Denise M. O'Gorman  Katherine Wakefield 《Journal of Equine Veterinary Science》2014

Management of the performance horse often incorporates meal feeding of highly digestible starches and reduced access to high-fiber forage. Such regimens are associated with equine gastric ulceration syndrome (EGUS) and can alter hindgut homeostasis. In-feed buffering of gastric contents and promotion of energy derivation from high-fiber forage in the hindgut are therefore desirable properties of a nutritional supplement. A marine-derived, multimineral supplement with known buffering properties containing calcium, magnesium, and short-chain fructo-oligosaccharides (scFOS) was tested under in vitro simulations of equine stomach and hindgut conditions. Six fiber:concentrate diets were incubated for 4 hours with or without the supplement at 37°C in pepsin HCl solution adjusted to pH 4.1 and 2.6. pH was measured at 1, 2, and 4 hours postincubation. Highest overall pH values were observed with the high cereal feeds; however, the supplement significantly increased (P < .001) the pH across all feeds by 0.17 and 0.19 for feeds incubated at pH 4.1 and 2.6, respectively. A gas production technique was used to measure the fermentation of four fiber:concentrate diets with and without additional supplement, using equine feces as the microbial inoculum. Addition of the supplement decreased (P < .05) the lag time and increased the initial fermentation rate, although as the incubation continued, this effect was reduced. These results demonstrate that the supplement had a significant buffering action for 4-6 hours under simulated in vitro stomach digestion conditions and also stimulated in vitro hindgut fermentation activities.  相似文献   

Lymphocystis disease in captive barramundi     

M PEARCE  JD HUMPHREY  AD HYATT  LM WILLIAMS 《Australian veterinary journal》1990,67(4):144-145

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Evaluation of auditory evoked potentials to predict depth of anaesthesia during fentanyl/fluanisone−midazolam anaesthesia in rats     

LM Antunes MSc  DVM    JV Roughan BSc  PhD  & PA Flecknell MA  Vet MB  PhD  DLAS  Dip ECVA 《Veterinary anaesthesia and analgesia》2001,28(4):196-203

Objectives To assess a method for monitoring depth of anaesthesia using components of middle latency auditory evoked potential (AEP) waveforms during anaesthesia with fentanyl/fluanisone and midazolam. Study design Prospective observational study. Animals Five female Wistar rats weighing between 210 and 250 g. Methods Implanted electrodes were used to record AEPs in animals receiving five doses of anaesthetic. Recordings were made at 5 minutes post‐injection (deep anaesthesia; no pedal withdrawal response, PWR) and then at 25 minutes (light anaesthesia; strong PWR). Responses showed five characteristic peaks occurring at 11, 14, 23, 42 and 68 ms that were measured for latency of occurrence and peak amplitude. Results Auditory evoked potential peaks P14, N23 and P42 were increased significantly in latency with successive anaesthetic injections [avg. F(1,4) = 12.53, p < 0.001; avg. F(1,4) = 10.6, p < 0.001; avg. F(1,4) = 3.9, p = 0.02, respectively]. Peak N23 showed a significant reduction in latency during the 20 minute recovery period following both the first and second anaesthetic injections (t(3) = 7.52, p = 0.005; t(4) = 5.17, p = 0.007, respectively). Peak P42 occurred significantly earlier 20 minutes following the second anaesthetic injection (t(4) = 4.75, p = 0.009). The mean overall depth of anaesthesia assessed using PWR scores was significantly correlated with the mean latency of peak N23, such that as the strength of PWR increased, N23 occurred significantly earlier (r = ?0.99, p = 0.01). The amplitude difference between peaks N23 and P42 increased after the second and third drug administrations [avg. F(1,4) = 10.65, p = 0.031 and avg. F(1,4) = 11.24, p = 0.028, respectively]. Conclusion The characteristics of these peaks, and in particular latency of peak N23, may provide a useful tool for assessing depth of anaesthesia produced by this, and possibly other anaesthetic agents.  相似文献   

Acquired proximal renal tubulopathy in dogs exposed to a common dried chicken treat: retrospective study of 108 cases (2007–2009)     

MF Thompson  LM Fleeman  AE Kessell  LA Steenhard  SF Foster 《Australian veterinary journal》2013,91(9):368-373

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Treatment response and long term follow up in nineteen dogs diagnosed with chronic enteropathy in Australia     

JRS Dandrieux  LM Martinez Lopez  N Prakash  CS Mansfield 《Australian veterinary journal》2019,97(9):301-307

Chronic enteropathy (CE) in dogs is common worldwide, but little data is available from Australia. The aim of this study was to describe treatment response and long‐term outcome in a cohort of dogs with CE. Dogs were prospectively enrolled at Murdoch University and the University of Melbourne. After diagnostic investigation to rule out diseases other than CE, dogs underwent sequential therapeutic trials until achieving a clinical response (diet then antibiotics, and finally immunosuppressants). Success was defined as 75% reduction of clinical severity for a minimum of five weeks. A total of 21 dogs were enrolled, and 19 completed the study. One dog was euthanised for lack of response to treatment and one excluded for lack of owner compliance. Most dogs responded to diet (n = 10), followed by antibiotics (n = 7) and immunosuppressants (n = 2). Long‐term remission (median 21.1 months, [3.0‐44.7]) was achieved in eight out of ten dietary responders without additional treatment. In contrast, only two dogs with antibiotic response remained in long‐term remission, of which one needed on‐going antibiotic treatment. Longer term remission was achieved in the two dogs treated with immunosuppressants with on‐going low dose therapy. This study concludes that most dogs referred for CE in Australia respond to dietary treatment (even after previous dietary interventions), and remission is long‐term compared to dogs treated with an antibiotic. Furthermore, the need for long‐term antibiotics in some dogs to maintain response may lead to antibiotic resistance. This study supports adequate dietary trials for CE in dogs, and a need for alternative second‐line treatments.  相似文献