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111.
Epizootiology of feline respiratory infections 总被引:2,自引:0,他引:2
D E Kahn T E Walton 《Journal of the American Veterinary Medical Association》1971,158(6):Suppl 2:955-Suppl 2:959
112.
Periparturient Merino ewes obtained from lines of sheep that had been selected either for increased resistance to Haemonchus contortus (R) or at random (C) were supplemented, while grazing at pasture, with either nil or 250 g/day cottonseed meal (CSM) for the 6 weeks prior to or the 6 weeks after the start of parturition. Ewes from both supplement groups had lower (mean 66% reduction) faecal egg counts (FECs) during the postpartum period and this coincided with a period of maternal body weight loss. Factors which increased the rate of maternal body weight loss, such as pregnancy and lactation status, also increased FEC. Evidence is presented that the magnitude of the periparturient rise (PPR) in FEC in grazing ewes will be greatest during periods of maternal weight loss and at these times supplementation to increase metabolisable protein (MP) supply will be most effective in increasing resistance to nematode parasites. The resistance of R ewes to nematode parasites was greater than that of C ewes throughout the experiment and was sufficiently low such that anthelmintic treatment in a commercial environment may not have been required. Irrespective of actual FEC, ewes from all treatment combinations exhibited a PPR in FEC. Reduced FEC of R ewes resulted in reduced apparent pasture larval contamination after 18 weeks of continuous grazing but supplementation was ineffective in this regard. It is suggested that integrated parasite management (IPM) programs for periparturient ewes should make use of both protein supplementation and genetic selection to increase worm resistance and reduce dependency on anthelmintics for worm control. 相似文献
113.
Various published systems for the prediction of dry matter (DM) intake are discussed, with special emphasis on their relationship to DM digestibility. Suggestions are made for the modification of the Conrad (1966) equations and their adaptation to different types of cattle and environment.The equations were included in a dynamic simulation model to test their accuracy in predicting weight changes in growing steers under grazing conditions in Botswana and the UK. It was found that predicted weights were generally within 0.4–1.5% of measured weights and that fluctuations in the predicted liveweight curves closely followed the pattern of the observed ones, showing that the equations can provide a sound basis for the prediction of DM intake in agricultural practice in general and in livestock simulation models in particular. 相似文献
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Kahn CR 《Science (New York, N.Y.)》2008,322(5901):542-543
117.
Kahn P 《Science (New York, N.Y.)》1993,260(5115):1744-1746
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119.
Beiersdorfer P Boyce KR Brown GV Chen H Kahn SM Kelley RL May M Olson RE Porter FS Stahle CK Tillotson WA 《Science (New York, N.Y.)》2003,300(5625):1558-1559
In laboratory experiments using the engineering spare microcalorimeter detector from the ASTRO-E satellite mission, we recorded the x-ray emission of highly charged ions of carbon, nitrogen, and oxygen, which simulates charge exchange reactions between heavy ions in the solar wind and neutral gases in cometary comae. The spectra are complex and do not readily match predictions. We developed a charge exchange emission model that successfully reproduces the soft x-ray spectrum of comet Linear C/1999 S4, observed with the Chandra X-ray Observatory. 相似文献