Farm management factors associated with bulk tank somatic cell count in Irish dairy herds     

PT Kelly  K O'Sullivan  DP Berry  SJ More  WJ Meaney  EJ O'Callaghan  B O'Brien 《Irish veterinary journal》2009,62(Z4):S45

The relationship between bulk tank somatic cell count (SCC) and farm management and infrastructure was examined using data from 398 randomly selected, yet representative, Irish dairy farms where the basal diet is grazed grass. Median bulk tank SCC for the farms was 282,887 cells/ml ranging from 82,209 to 773,028 cells/ml. Two questionnaires were administered through face-to-face contact with each farmer. Herd-level factors associated with bulk tank SCC were determined using linear models with annual somatic cell score (i.e., arithmetic mean of the natural logarithm of bulk tank SCC) included as the dependent variable. All herd level factors were analysed individually in separate regression models, which included an adjustment for geographical location of the farm; a multiple regression model was subsequently developed. Management practices associated with low SCC included the use of dry cow therapy, participation in a milk recording scheme and the use of teat disinfection post-milking. There was an association between low SCC and an increased level of hygiene and frequency of cleaning of the holding yard, passageways and cubicles. Herd management factors associated with bulk tank SCC in Irish grazing herds are generally in agreement with most previous studies from confinement systems of milk production.  相似文献   

Tropical ecosystems into the 21st century     

Bawa KS  Kress WJ  Nadkarni NM  Lele S  Raven PH  Janzen DH  Lugo AE  Ashton PS  Lovejoy TE 《Science (New York, N.Y.)》2004,306(5694):227-228

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L-dopa in legume seeds: a chemical barrier to insect attack     

Rehr SS  Janzen DH  Feeny PP 《Science (New York, N.Y.)》1973,181(4094):81-82

Seeds of the genus Mucuna display both a remarkable immunity to attack by seed-eating insects and an unustially high concentration of free L-dopa. When seed powders or pure L-dopa were incorporated into artificial diets and fed to southern armyworm larvae, mortality increased, and abnormal pupae and adults resulted. At higher concentrations L-dopa acted as a feeding repellent.  相似文献   

Yucatan meteor: the real impact     

Janzen DH 《Science (New York, N.Y.)》1992,258(5085):1071

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Influence of the type of mineral soil on the uptake of dieldrin by wheat seedlings     

J G Saha  J C Karapally  W K Janzen 《Journal of agricultural and food chemistry》1971,19(5):842-845

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Pseudomyrmex nigropilosa: A Parasite of a Mutualism     

Janzen DH 《Science (New York, N.Y.)》1975,188(4191):936-937

Pseudomyrmex nigropilosa is a parasite ofthe ant-acacia mutualism in Central America in that it harvests the resources of swollen-thorn acacias but does not protect the acacias. In the process, it also lowers the rate of occupation by the obligate acacia-ants, species of ants that do protect swollen-thorn acacias. Tenancy ofan acacia by P. nigropilosa must be temporary, since the unoccupied plant is shortly killed by herbivores or competing plants, or is taken over by obligate acacia-ants. As expected of a species of short-lived ant, a P. nigropilosa colony produces reproductives earlier in the life of the colony and maintains fewer grams of workers per gram of brood than does a colony of the long-lived obligate acacia-ants.  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   

Investigation of pregnancy losses in beef cattle herds associated with Neospora sp. infection.   总被引：1，自引：1，他引：0       下载免费PDF全文

B R Hoar  C S Ribble  C C Spitzer  P G Spitzer    E D Janzen 《The Canadian veterinary journal. La revue veterinaire canadienne》1996,37(6):364-366

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Interstitial pneumonia in feedlot cattle: concurrent lesions and lack of immunohistochemical evidence for bovine respiratory syncytial virus infection.     

S D Sorden  R W Kerr  E D Janzen 《Journal of veterinary diagnostic investigation》2000,12(6):510-517

The objectives of this study were to describe the nature and distribution of microscopic lung lesions in feedlot cattle with interstitial pneumonia and to determine whether bovine respiratory syncytial virus (BRSV) antigen was present in affected lungs. Lungs with macroscopic lesions compatible with interstitial pneumonia were collected from cattle from 5 west-central Saskatchewan feedlots that had been on feed for greater than 60 days at the time of death. Interstitial pneumonia was most consistently present in dorsal portions of caudal lung lobes and in 21/28 cases (75%) had a multifocal to coalescing distribution. All 28 lungs exhibited hyaline membrane formation and some degree of type II alveolar epithelial cell hyperplasia, consistent with an acute to subacute duration. Twenty-one of 28 cases (75%) had concurrent bronchopneumonia in at least 1 lung lobe; bronchopneumonia was grossly evident in 9/28 cases (32%). Chronic bronchitis or bronchiolitis was present in at least 1 section in 12/28 (43%) of the lungs, and 25/28 (89%) had at least 1 focus of bronchiolitis fibrosa obliterans. Bronchopneumonia and bronchiolitis fibrosa obliterans were markedly less common in 10 sets of bovine lungs obtained from an abattoir. Bovine respiratory syncytial virus antigen was demonstrated using immunohistochemistry in 2/28 cases and was associated with bronchiolar epithelial necrosis that was more severe than the bronchiolar lesions in the BRSV antigen-negative cases. Interstitial pneumonia in feedlot cattle in this study was more frequently associated with suppurative bronchopneumonia and bronchiolitis fibrosa obliterans than with BRSV infection.  相似文献   

氮肥用量和水分淋溶对土壤和小麦氮素平衡的影响   总被引：3，自引：0，他引：3  

郭建华  Henry Janzen 《土壤通报》2000,31(6):259-261

:利用标记15N尿素研究不同施肥量和淋溶对小麦生长的影响 ,结果表明水分淋溶对小麦生长的影响不明显 ;地上部生物产量与肥料利用率成正相关 .小麦根系越发达 ,收集到的淋溶液越少 ,损失的肥料N越少 .施用相同量的氮肥 ,淋溶处理的氮肥利用率略低于正常浇水的处理  相似文献