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   

Development of enzymes for robust aryloxyphenoxypropionate and synthetic auxin herbicide tolerance traits in maize and soybean crops     

Clayton T Larue  Michael Goley  Lei Shi  Artem G Evdokimov  Oscar C Sparks  Christine Ellis  Andrew M Wollacott  Timothy J Rydel  Coralie E Halls  Brook Van Scoyoc  Xiaoran Fu  Jeffrey R Nageotte  Adewale M Adio  Meiying Zheng  Eric J Sturman  Graeme S Garvey  Marguerite J Varagona 《Pest management science》2019,75(8):2086-2094

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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   

Intraoral acrylic splint application     

Niemiec BA 《Journal of veterinary dentistry》2003,20(2):123-126

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Postcards from the past: charting the landscape-scale conversion of tropical Australian savanna to closed forest during the 20th century     

Barry W. Brook  David M. J. S. Bowman 《Landscape Ecology》2006,21(8):1253-1266

Repeated sequences of digitised and geo-referenced historical aerial photography provide a powerful means of understanding landscape change. We use this method to demonstrate a landscape wide expansion of closed forest (42% increase in total coverage) in the Australian monsoon tropics over the past five decades. Retrospective habitat suitability models (HSI) of closed forest derived using four landscape measures (drainage distance, slope angle, aspect and elevation) for imagery taken in 1947 correctly forecast the subsequent spatial distribution of the expansion, with topographic fire protection primarily determining the closed-forest distribution. The dynamics of the closed forest-savanna boundary were predicted accurately by generalised linear models, with closed-forest expansion in fire-protected sites along forest edges and regression in the more fire-prone areas. Two factors may plausibly explain the expansion of closed forests. First, eco-ethnographic records stress the skilful use of fire by Aboriginal people in protecting isolated and locally resource-rich closed-forest patches. Second, the recent global increase in atmospheric CO₂ may be changing the competitive balance between savanna and forest by enabling C₃ trees to grow fast enough to escape the fire trap presented by flammable C₄ grasses.  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   

Bilateral laryngeal paralysis in the horse     

I D Duncan  D Brook 《Equine veterinary journal》1985,17(3):228-233

Four two-year-old Thoroughbreds suffered an acute gastrointestinal illness shortly after dosing with mineral oil which was thought to have been contaminated with an organophosphate compound. Three weeks later all four were noted to be dyspnoeic and endoscopic examination showed that they had developed bilateral laryngeal paralysis. Two of the horses died during severe bouts of dyspnoea six and eight months later and the third was killed shortly thereafter. Examination of the left and right recurrent laryngeal nerves from these horses showed a severe loss of myelinated fibres distally, especially in the left nerve. A similar but less severe lesion was seen in other long peripheral nerves, including the phrenic and digital nerves of the third horse. The spinal cord in two horses showed evidence of mild axonal degeneration which was not related to a particular tract or location. The fourth horse had bilateral laryngeal paralysis two years later. The acute clinical signs and delayed neurological sequelae seen in these horses were strongly suggestive of accidental organophosphate toxicity.  相似文献   

Pragmatic population viability targets in a rapidly changing world   总被引：1，自引：0，他引：1  

Lochran W. Traill  Barry W. Brook  Corey J.A. Bradshaw 《Biological conservation》2010,143(1):28-34

To ensure both long-term persistence and evolutionary potential, the required number of individuals in a population often greatly exceeds the targets proposed by conservation management. We critically review minimum population size requirements for species based on empirical and theoretical estimates made over the past few decades. This literature collectively shows that thousands (not hundreds) of individuals are required for a population to have an acceptable probability of riding-out environmental fluctuation and catastrophic events, and ensuring the continuation of evolutionary processes. The evidence is clear, yet conservation policy does not appear to reflect these findings, with pragmatic concerns on feasibility over-riding biological risk assessment. As such, we argue that conservation biology faces a dilemma akin to those working on the physical basis of climate change, where scientific recommendations on carbon emission reductions are compromised by policy makers. There is no obvious resolution other than a more explicit acceptance of the trade-offs implied when population viability requirements are ignored. We recommend that conservation planners include demographic and genetic thresholds in their assessments, and recognise implicit triage where these are not met.  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   

Simulation of forage harvest and conservation on dairy farms     

P. Savoie  L.D. Parsch  C.A. Rotz  R.C. Brook  J.R. Black 《Agricultural Systems》1985,17(2):117-131

A computer model was developed to simulate forage systems on dairy farms. The model simulated alfalfa growth, corn silage and corn grain yields, harvest, storage, feeding and ration formulation for a dairy herd. A 26-year series of historical weather data from East Lansing, Michigan, was used to compare management and technological alternatives on the basis of average net return and year-to-year variations. For example, a four-cut alfalfa system was found to be more profitable than a three-cut system 90% of the time. The comparison of a hay system with a silage system was very sensitive to forage intake assumptions; the break-even point shifted from 120 ha to 40 ha when silage intake was increased by 5%. The model can be used to assess the impact of new forage conservation methods under a wide range of climatic and management conditions.  相似文献