Management of gastrointestinal nematode parasites on sheep farms in New Zealand     

KE Lawrence  DM Leathwick  AP Rhodes  R Jackson  C Heuer  WE Pomroy 《New Zealand veterinary journal》2013,61(5):228-234

AIM: To report current farmer opinions and farming practices relating to control of gastrointestinal nematodes and anthelmintic resistance on sheep farms in New Zealand.

METHODS: An interview-based cross-sectional study of grazing management and anthelmintic useage was conducted by veterinarians on 80 randomly selected sheep farms in New Zealand.

RESULTS: Useable data were returned by 74/80 (92%) farmers who participated in the study. However, despite contacting 400 farmers the target sample size of 100 farms was not reached. The results indicated that only 31% of farms had previously tested for drench resistance, that effective quarantine-drenching of imported stock was not always carried out, and that farmers were more likely to integrate cattle than ewes into their grazing management of lambs. Furthermore, the number of drenches given to lambs had changed little in 25 years. The use of faecal egg counting by farmers has increased.

CONCLUSIONS: Dependence on anthelmintics continues to be high on sheep farms in New Zealand. Whilst the number of drench treatments has changed little, there is more widespread use of persistent or long-acting treatments. Farmers need to be encouraged to monitor the resistance status of nematode populations on their farms and use this information to develop strategies aimed at maintaining susceptible alleles within the parasite populations and conserving the efficacy of existing drug families.  相似文献   

A comparison of a rising-plate meter and an electronic capacitance meter for estimating the yield of pastures grazed by dairy cows     

C. R. STOCKDALE  K. B. KELLY 《Grass and Forage Science》1984,39(4):391-394

The performances of a rising-plate meter and a single-probe electronic capacitance meter were compared for estimating the herbage mass of irrigated pastures both before and after grazing by dairy cows. Mean CV for the rising plate meter and the single-probe meter were 12.7% and 13.3% respectively when herbage mass was measured before grazing, and 21.8% and 15.4% respectively immediately after grazing. These coefficients of variation indicate that while the performance of the two meters was similar when herbage mass was measured before grazing, the single-probe meter was a more precise instrument for estimating herbage mass after grazing.
Trampling of herbage prior to measurement had a major effect on the regressions of both meters; the regression intercept was increased by 2800 kg dry matter (DM) ha⁻¹ for the rising-plate meter and by 2580 kg DM ha⁻¹ for the single-probe meter. The slopes of the graphs, however, remained unchanged.
It was concluded that while the single-probe meter performed better than the rising-plate meter for estimating the mass of post-grazing herbage when trampling was negligible, the large effect that trampling had on the post-grazing calibration regressions precluded both instruments from general use in dairy cattle research. This indicates that another technique is required in circumstances in which pastures are heavily trampled.  相似文献   

Radiation dose rate and mutation frequency     

RUSSELL WL  RUSSELL LB  KELLY EM 《Science (New York, N.Y.)》1958,128(3338):1546-1550

New data have clearly confirmed the earlier finding that specific locus mutation rates obtained with chronic gamma irradiation of spermatogonia are lower than those obtained with acute x-rays. Since this result is in contrast to classical findings for Drosophila spermatozoa, and apparently contradicts one of the basic tenets of radiation genetics, it was important to determine what factors were responsible for it. Experiments undertaken for this purpose reveal the following: (i) the lower mutation frequency is due mainly to difference in dose rate of radiation, rather than quality; (ii) a dose-rate effect is not obtained in experiments with mouse spermatozoa, confirming classical findings for spermatozoa, and indicating that the explanation for intensity dependence in spermatogonia resides in some characteristic of gametogenic stage; and (iii) a dose-rate effect is found not only in spermatogonia but also in oocytes, where cell selection is improbable, indicating that the radiation intensity effect is on the mutation process itself. A threshold response for all mutations in spermatogonia and oocytes is not a necessary consequence of the findings. Plausible hypotheses consistent with the present results can lead to other predictions. From a practical point of view, the results indicate that the genetic hazards, at least under some radiation conditions, may not be as great as those estimated from the mutation rates obtained with acute irradiation. However, it should not be forgotten that even the lower mutation rates obtained with the present intensity levels are still appreciable (16).  相似文献   

Colossal Magnetoresistance Without Mn3+/Mn4+ Double Exchange in the Stoichiometric Pyrochlore Tl2Mn2O7     

MA Subramanian  BH Toby  AP Ramirez  WJ Marshall  AW Sleight  GH Kwei 《Science (New York, N.Y.)》1996,273(5271):81-84

Structural analysis from powder neutron and single-crystal x-ray diffraction data for a sample of the Tl2Mn2O7 pyrochlore, which exhibits colossal magnetoresistance (CMR), shows no deviations from ideal stoichiometry. This analysis gives an Mn-O distance of 1.90 angstroms, which is significantly shorter than the Mn-O distances (1.94 to 2.00 angstroms) observed in phases based on LaMnO3 perovskites that exhibit CMR. Both results in Tl2Mn2O7 indicate oxidation states very close to Tl23+Mn24+O7. Thus, Tl2Mn2O7 has neither mixed valence for a double-exchange magnetic interaction nor a Jahn-Teller cation such as Mn3+, both of which were thought to have an important function in CMR materials. An alternate mechanism for CMR in Tl2Mn2O7 based on magnetic ordering driven by superexchange and strong spin-fluctuation scattering above the Curie temperature is proposed here.  相似文献   

Numbers of fungi and bacteria in transatlantic air     

PADY SM  KELLY CD 《Science (New York, N.Y.)》1953,117(3048):607-609

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'Aquaculture and Water Resource Management': An International Symposium held at the University of Stirling, 21-25 June 1994     

LIAM A KELLY  MALCOLM C M BEVERIDGE  DONALD J BAIRD  JAMES F MUIR 《Aquaculture Research》1995,26(9):617-617

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Ultrastructure of Thelohania duorara Iversen & Manning, 1959 (Microspora, Thelohaniidae) in the Pink Shrimp, Penaeus duroarum Burkenroad     

E. S. IVERSEN  J. F. KELLY  D. ALZAMORA 《Journal of fish diseases》1987,10(4):299-307

Abstract. The structure of Thelohania duorara Iversen & Manning, 1959, a micro-sporidian parasite of pink shrimp. Penaeus duorarum Burkenroad, was examined with electron microscopy. Earliest developmental stages observed were limited to diplokaryotic cells. Both microtubules associated with exospore formation, and hair-like filaments, projecting from the outer surface of the exospore, were observed during sporogony. The continuity of the cisternae of the polaroplast, the perinuclear cisterna, the outer membrane of the polar filament and membranes surrounding masses of secretion granules were noted. Mature spores had a granular endospore and hair-like filamentous projections on the exospore surface. The polar filament made 13–14 turns, the most distal being slightly constricted. Information presented here indicates that T. duorarum should be retained within the genus Thelohania as it is now defined.  相似文献   

A comment on the influence of dingoes on the Australian sheep flock     

DM Forsyth  AP Woolnough  DG Nimmo  EG Ritchie  M Kennedy  A Pople  I Watson 《Australian veterinary journal》2014,92(12):461-462

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OBITUARY     

JOHN KELLY 《Australian veterinary journal》1997,75(12):913-913

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Pseudomonas mastitis in a dairy herd   总被引：1，自引：0，他引：1  

MW McLENNAN  WR KELLY  D. O'BOYLE 《Australian veterinary journal》1997,75(11):790-792

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