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A case of selenium poisoning was suspected following the administration of 325 micromol selenium a day as sodium selenate (25 mg Se) for five consecutive days. The main signs were confined to changes in the integument which were loss of hair from the mane and tail, disintegration of the skin of the anus, lips, prepuce and scrotum, and separation of the hooves from the coronary corium. Periodic analyses of blood, hair and hoof parings from the sole correlated strongly with blood and identified horn and hair as important additional routes of excretion. 相似文献
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Sources of stray electrical leakage from Power Supply Authority alternating current (AC), fence energiser pulses and randomly generated pulses and spikes on 55 dairy farms in the Waikato area were identified between December 1986 and March 1988. The electrical measurements were made using a specifically designed voltmeter able to detect voltages between 0.1V and 1500V, from single voltage spikes of two microseconds or greater duration from direct current (DC) as well as 50 Hz AC. Ninety-five sources of stray voltage were identified, and 53 per cent of properties had more than one source of >0.5V. The major source was from electric fence energisers. Rotary platform parlours were among the commonest sources of random or transient voltage spikes. Leakage of AC into one or other of the components of the milk transport system such as vat, plate cooler, milk lift pump and milk line was common. Owners acknowledged the improvements in milk production, reproductive performance and growth rate of calves after reduction of the exposure of dairy cattle to stray electrical leakage. A representative summary of five case records helps define the range of improvements that may possibly be achieved. 相似文献
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The copper status of dairy herds in the Waikato, Taranaki and Northland regions between 1 August and 30 September was assessed by copper determinations made on composite sera from ten cows in each herd. Comparisons were made between two major groups categorised as as received and supplemented. In the latter, the cows received 2.0-6.0 g/day of copper sulphate orally from late gestation to the end of lactation. Mean copper values were determined from pastures in Taranaki and Northland and from pastures from three soil types in the Waikato. The lowest were in Northland (134.3 micromol/kg) and the highest in Taranaki (173.3 micromol/kg). Calculated dietary available copper levels showed the lowest were from pastures grown on organic soils in the Waikato. These soils also had high molybdenum levels. Serum copper values as received were lowest in Northland (7.30 micromol/l), and were marginal for both Taranaki (9.91 micromol/l) and the Waikato (9.93 micromol/l). The levels in supplemented herds were considerably higher, i.e. from the Waikato 11.7 micromol/l and from Taranaki 11.5 micromol/l. When liver and serum copper levels from paired samples were compared there was a reasonable correlation (r = 0.64) but the standard deviation approximated the mean liver copper level, i.e. 155 +/- 141 micromol/l. 相似文献
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Nitrate determination in leachates from farmyard manure by UV absorption A simple, sufficiently sensitive (< 1 ppm NO3?-N) method for nitrate determination in leachates from farmyard manure is described, suitable for routine analysis. The well known determination by UV absorption is preceded by a precipitation of organic matter with ZnSO4BO7. By this, average NO3?-N contents of 48.7 ppm were detected in leachates from cattle manure heaps (n = 54). 相似文献
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Uptake and distribution of nitrogen in old and new German summer wheats
Five old German summer wheat varieties, bred in the first third of this century, were compared with five new varieties in an outdoor pot trial. The modern genotypes had taken up slightly more N, both at anthesis and at maturity. At anthesis, N percentage in all organs was considerably higher for modern cultivars. This resulted mainly from a dilution effect caused by superior dry masses of old varieties. Modern genotypes accumulated more N in the upper leaves and ears. As compared with the old varieties, less N was found in the stems of the new cultivars. At maturity, N concentration in vegetative organs was simular for both groups of varieties. N percentage of grains was higher for old cultivars. However, the new genotypes achieved higher N yields. This resulted in part from the slightly higher assimilation of N. Moreover, new genotypes were superior in N translocation which was reflected by higher nitrogen harvest indexes. The postfloral loss of N from the vegetative tissue depended on the organ and the age of the varieties. 相似文献
Five old German summer wheat varieties, bred in the first third of this century, were compared with five new varieties in an outdoor pot trial. The modern genotypes had taken up slightly more N, both at anthesis and at maturity. At anthesis, N percentage in all organs was considerably higher for modern cultivars. This resulted mainly from a dilution effect caused by superior dry masses of old varieties. Modern genotypes accumulated more N in the upper leaves and ears. As compared with the old varieties, less N was found in the stems of the new cultivars. At maturity, N concentration in vegetative organs was simular for both groups of varieties. N percentage of grains was higher for old cultivars. However, the new genotypes achieved higher N yields. This resulted in part from the slightly higher assimilation of N. Moreover, new genotypes were superior in N translocation which was reflected by higher nitrogen harvest indexes. The postfloral loss of N from the vegetative tissue depended on the organ and the age of the varieties. 相似文献
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Materials performance in structural applications is often restricted by a transition from ductile response to brittle fracture with decreasing temperature. This transition is currently viewed as being controlled either by dislocation mobility or by the nucleation of dislocations. Fracture experiments on tungsten single crystals reported here provide evidence for the importance of dislocation nucleation for the fracture toughness in the semibrittle regime. However, it is shown that the transition itself, in general, is controlled by dislocation mobility rather than by nucleation. 相似文献
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A limited field study of covered facilities used for raising dairy calves suggested that respiratory disorders and death rates were highest when calves were continuously housed on bedding composed of wood shavings, where ventilation was poor and where automatic feeders were installed. High concentrations of ammonia were found in the urine-soaked bedding following overnight incubation. A prolific growth of mixed micro-organisms isolated from the shavings rapidly colonised plates of selective urea medium. Death rates of 10% and 13.5% were observed on two properties. Respiratory distress was common and lung disease was intractable to treatment on these farms. A histopathological diagnosis of subacute purulent pneumonia with distal necrotising bronchiolitis was made, similar to lung lesions produced experimentally in cats, guinea pigs and rabbits exposed to ammonia gas. 相似文献