The intensity of resistance by mature Merino ewes against Haemonchus contortus and Tichostrongylus colubriformis in single-species and combined-species infection     

DB ADAMS  JJ LYNCH†  BH ANDERSON  LR FELL‡  GN HINCH§  RK MUNRO¶ 《Australian veterinary journal》1990,67(12):443-445

Three-year-old, non-lactating and non-pregnant Merino ewes, raised on pasture under a program of strategic treatment with anthelmintic and found to be extremely resistant to "trickle" infection with Haemonchus contortus, were given single-dose infections with either H. contortus or Trichostrongylus colubriformis or both species together. The purpose was to ascertain the intensity of protective immunity against the 2 parasites in sheep with immunity acquired from a presumably slight exposure to infection. To provide a criterion, some infected ewes were immunosuppressed with corticosteroid, dexamethasone. Untreated ewes were extremely resistant to challenge infection with either 15,000 or 150,000 H. contortus or 15,000 T. colubriformis. Surprisingly, when mixed infection was given, egg counts for H. contortus were significantly elevated compared with infection by that species alone. Antibody to antigens from infective larval and adult H. contortus was measured in serum by enzyme-linked-immunosorbent assay (ELISA) during the course of infection. Serum titres against larval antigens were significantly depressed when infections with either H. contortus or T. colubriformis were permitted by immunosuppression with dexamethasone, whereas those against adult antigen were depressed when infection with T. colubriformis was permitted.  相似文献   

Greenhouse gas mitigation potential of agricultural land in Great Britain     

N. Fitton  C. P. Ejerenwa  A. Bhogal  P. Edgington  H. Black  A. Lilly  D. Barraclough  F. Worrall  J. Hillier  P. Smith 《Soil Use and Management》2011,27(4):491-501

The aim of this paper is to assess the greenhouse gas (GHG) mitigation potential of croplands and grasslands in Great Britain under different management practices. We consider the feasible land management options for grass and cropland using county level land‐use data with estimates of per‐area mitigation potential for individual and total GHGs, to identify the land management options with the greatest cost‐effective mitigation potential. We show that for grasslands, uncertainties still remain on the mitigation potential because of their climatic sensitivity and also their less intensive management. For croplands in Great Britain, the technical mean GHG mitigation potentials for all cropland management practices range from 17 Mt CO₂‐eq. per 20 yr to 39 Mt CO₂‐eq. per 20 yr. There are significant regional variation in all cases, with the greatest potentials in England, negligible potential in Wales and intermediate potential in Scotland, with country differences largely driven by the areas of cropland and grassland in each country. Practices such as agronomic improvement and nutrient management are the most promising options because of their impact on N₂O emissions and also their larger potential at low cost. In terms of annual emissions from agriculture, calculated mitigation potentials are small, where the technical mitigation potential of agronomy and nutrient management strategies are ca. 4.5 and 3.8%, respectively (agricultural emissions account for ca. 9% or 47.7 Mt CO₂‐eq., of total Great Britain GHG emissions, Department of Energy and Climate Change, UK). However when compared with the land use, land‐use change and forestry sector (LULUCF) emissions, nutrient management would reduce further emission reductions by approximately half of the 2005 LULUCF sink (i.e. ?1.6 Mt CO₂‐eq. per year).  相似文献   

The effects of duration and concentration of plasma progesterone on the fertility of post-partum cows treated with pregnant mare serum gonadotrophin and intravaginal progesterone     

RK MUNRO 《Australian veterinary journal》1989,66(2):43-45

The effects of duration of insertion of progesterone releasing devices (PRIDs) on the concentrations of plasma progesterone (plasma P4) and the relationship of these with fertility were examined respectively in ovariectomised and intact Bos taurus cattle. In experiment 1, ovariectomised cows (n = 14) were treated with PRIDs to produce high and low plasma P4 for 7 or 14 days giving 4 treatment groups designated H7, H14, L7 or L14. Mean plasma P4 in the H14 and L14 groups were 6.6 and 6.0 ng/ml respectively, during the first week and 5.4 and 3.8 ng/ml respectively, during the second. Mean plasma P4 of 6.3 and 4.2 ng/ml were observed in H7 and L7. In experiment 2, suckled cows (n = 171) received the same PRID treatments as cows in experiment 1, plus either 375 or 750 iu pregnant mare serum gonadotrophin, and subsequent calving rates were recorded. These were significantly lower after L7 than the other treatments (12% v 38%, P less than 0.025). These results showed that fertility after oestrus was closely related to plasma P4 observed before oestrus and indicated that treatment with progesterone for as little as 1 week can produce normal fertility providing plasma P4 attain a critical threshold during treatment.  相似文献   

Effects of suckling on oestradiol benzoate induced LH release in post-partum, ovariectomised cows     

RK MUNRO 《Australian veterinary journal》1990,67(9):313-315

Twelve suckling and 12 non-lactating post-partum cows were treated with a progesterone-releasing pessary for 7 or 14 d followed by an injection of 500 micrograms oestradiol benzoate (ODB) 24 h after pessary removal or no injection. Suckling had no significant effect on plasma progesterone concentrations (plasma P4) or plasma luteinising hormone concentrations (plasma LH) during pessary insertion. After pessary removal plasma LH rose in response to ODB. The extent of the rise was similar in suckling and non-lactating cows treated with progesterone for 14 d but was significantly lower in non-lactating than suckling cows (P less than 0.025) treated for 7 d. These findings indicate that suckling increases the responsiveness of plasma LH in post-partum cows following progesterone and oestrogen treatment compared to non-lactating cows and that extended treatment with progesterone can remove this difference.  相似文献   

Animal health monitoring and surveillance in Switzerland     

KDC STÄRK 《Australian veterinary journal》1996,73(3):96-97

Switzerland has traditionally used a passive disease reporting system for all notifiable diseases. This type of system is not suitable for the documentation of very low prevalences (freedom from disease), sub-clinical cases and non-notifiable diseases. In order to meet the high international standards for animal health surveillance and to fulfil the general need for sound animal health data, Switzerland has evaluated the feasibility of modern monitoring and surveillance concepts. In general, the principle of active surveillance has been acquired and is now being applied whenever possible. In this paper, several examples of Swiss surveillance systems are presented and discussed. They include systematic testing of random population samples, carcase screening at abattoirs and sentinel herd monitoring.  相似文献   

Comparison between the seminal and nodal root systems of winter wheat in their activity for N and K uptake     

H. Kuhlmann  P. B. Barraclough 《植物养料与土壤学杂志》1987,150(1):24-30

The activity of seminal and nodal root systems of winter wheat (cv. Avalon) in taking up NO₃^? and K⁺ has been measured in solution culture using a split root technique. Plants in the tillering phase of growth (36 days old) were used for the experiment which lasted 20 days. During this time plant dry weights increased by a factor of 20, whilst root: shoot ratios and nutrient compositions remained constant. Inflows (uptake rate per unit root length) were 2–6 times higher for the nodal roots than for the seminal roots, with values varying between 1 and 9 pmol cm^?1 s^?1 for N and between 0.5 and 4 pmol cm^?1 s^?1 for K. When uptake was expressed on the basis of unit fresh weight of roots, values ranged from 1 to 2.3 pmol mg^?1 s^?1 for N and from 0.4 to 1.0 pmol mg^?1 s^?1 for K, and there were only very small differences in uptake efficiency between the nodal and seminal roots. Uptake rate per unit root decreased with plant age. This was caused by a decline in shoot demand due to the reduction of the relative growth rate. When either the nodal or seminal root system alone was supplied with nutrients, uptake rate per unit root increased and nutrient uptake per plant reached 72–92% of the control.  相似文献   

Comparative Earth History and Late Permian Mass Extinction   总被引：6，自引：0，他引：6  

AH Knoll  RK Bambach  DE Canfield  JP Grotzinger 《Science (New York, N.Y.)》1996,273(5274):452-457

The repeated association during the late Neoproterozoic Era of large carbon-isotopic excursions, continental glaciation, and stratigraphically anomalous carbonate precipitation provides a framework for interpreting the reprise of these conditions on the Late Permian Earth. A paleoceanographic model that was developed to explain these stratigraphically linked phenomena suggests that the overturn of anoxic deep oceans during the Late Permian introduced high concentrations of carbon dioxide into surficial environments. The predicted physiological and climatic consequences for marine and terrestrial organisms are in good accord with the observed timing and selectivity of Late Permian mass extinction.  相似文献   

The Kinetics of Spinning-Disc Atomizers Applied to Seed Treatment Machinery¹     

I. GYÜRK 《EPPO Bulletin》1983,13(3):475-478

Spinning disc-atomizers are widely used in seed-dressing machines. They not only give an initial velocity to the droplet but deliver air as well, consequently the droplet enters a moving medium. Computer analysis shows the influence of this mutual motion in the case of linear, parabolic and hyperbolic air velocity decrease. The moving air exerts a significant effect on the ideal encounter zone of liquid and seed. This effect should be taken into consideration in designing the dressing chamber of seed treatment machinery.  相似文献   

Reply     

RK WANSBROUGH 《Australian veterinary journal》1996,74(6):476-477

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2.7 Cabbage Root Fly on Brussels sprouts in Warwickshire, 1963     

K. J. Coghill  Ruth M.  Barraclough 《Plant pathology》1965,14(S1):10-11

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