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J. Beattie 《British poultry science》1964,5(3):269-276
Measurements of the oxygen uptake and carbon dioxide output during the last 36 hr. of incubation show that the exchange of these two gases increases progressively from the start of pulmonary respiration until hatching. The evidence indicates that prior to the penetration of the shell by the beak of the embryo (” pipping “) there is marked hypoxia and hypercapnia which are relieved when the embryo gains access to atmospheric air. At the time of hatching there is a very rapid release of carbon dioxide from the body surface and the internal surface of the allantoic membranes. There is no evidence to suggest that its release indicates either hypoxia or hypercapnia in the embryo immediately before hatching. 相似文献
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1998-2000年在浙江黄岩进行了窄幅机油乳剂(敌死虫)对柑桔的安全性试验。每年的4月下旬至10月上旬在温州蜜柑果园中分别用.5%的敌死虫定期喷洒4-10次(盛夏高温季节在16:00后喷洒),结果表明,除在花蕾期使用会增加畸形花率,9月份以后喷洒使果实的日灼病斑稍趋明显之外,对落叶落果、果实的产量和质量等均无不良影响,但一年的累积用量宜控制在4%以下。 相似文献
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The long-term variation in yield of English apple orchards and of 2 main cultivars are examined. Three factors determining yield are specified: the weather, the alternate-year bearing character of apple trees, and the technology (the introduction of semi-dwarfing rootstocks, higher-density plantings and new management techniques) as represented by time. Time was the most significant factor in increasing yields in the long term. Weather, particularly during the pre-flowering period was shown markedly to affect the crop from season to season. The model developed can be used to predict current production up to 5 months before harvest.When yield varies widely from year to year, a decrease in the area cropped has little effect on production and hence policies aimed at marginally reducing orchard area would have little short-term effect on overall production. 相似文献
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AIM: To identify feeding and management variables associated with variation in faecal pH within a population of intensively managed Thoroughbred racehorses in New Zealand. METHODS: A cross-sectional survey was conducted of 16 racehorse trainers in the North Island of New Zealand. Interviews were conducted at the trainers' stables to obtain information on feeding and management of horses, and faecal samples were collected and faecal pH measured. RESULTS: Ninety-seven percent of the horses surveyed were confined in an area ≤5 × 5 m for ≥12 h/day. Trainer's age, number of years they had trained horses, age and gender of horses, weeks in race training, racing class, frequency of feeding, bedding type, and exercise workload had no effect on mean faecal pH. Acidic faecal pH (pH ≤6.32) was associated with stables with ≤12 horses, and trainers at stables with ≤12 horses offered more concentrate feed than those at stables with >12 horses. Acidic faecal pH was associated with trainers who offered 4 kg of grain as the only form of concentrate fed, or offered ≤2.25 kg hay/day. Horses that displayed stable vices had less acidic faecal pH than horses that did not display stable vices, viz pH 6.70 (standard error of the mean (SEM) 0.135) vs 6.43 (SEM 0.029) (p=0.04). CONCLUSIONS AND CLINICAL RELEVANCE: Racehorse management in New Zealand is similar to that observed in other major racing countries. Trainers with ≤12 horses fed more concentrates and their horses had lower faecal pH than those of trainers with >12 horses. Irrespective of management system, it appears important to provide at least 2.25 kg of hay/day ad libitum, to buffer hindgut acidosis associated with diets high in soluble carbohydrate. 相似文献
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