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1.
Modelling the effect of weed-seed distribution in the soil profile on seedling emergence 总被引:3,自引:0,他引:3
Experiments to monitor weed seedling emergence from various soil depths were begun in 1989. Recently shed seeds were buried in either narrow bands at a range of depths in the soil or mixed evenly between the soil surface and each of these depths. Total emergence of Stellaria media (L.) Vill., Matricaria spp., Veronica persica Poiret, Veronica arvensis L. and Polygonum aviculare L., declined with increasing depth of burial. A similar pattern was observed for Chenopodium album L. with the exception of emergence from the surface layer. The reduction in emergence with increasing soil depth was greater for seeds in the narrow-banded treatments than for those in broad layers. A model was developed using the data from the narrow-banded treatments to predict emergence from distributions over broad layers. Predictions from the model closely agree with the data from the present broad-layer treatments and those from a similar experiment made in the 1960s. By including the effects of depth of seed burial on seedling emergence, this model could be combined with models that determine the effects of cultivation on seed distribution, and therefore improve precision of predictions of seedling emergence from the seedbank. 相似文献
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D. E. JACOBS M. T. FOX J. G. PILKINGTON D. B. ROSS W. G. RYAN† 《Journal of veterinary pharmacology and therapeutics》1989,12(4):444-450
Seeder calves infected with Dictyocaulus viviparus were used to contaminate a field divided into three similar paddocks. Twenty-four autumn-born calves were allocated to three matched groups; one group was given topical ivermectin treatments (0.5 mg/kg) at 3, 8 and 13 weeks after turnout (Day 0); each member of a second group was given an oxfendazole pulse-release intraruminal device (OPRB) at turnout; while a third group was kept as untreated controls to monitor the natural epidemiological pattern of events. Severe pasteurella pneumonia exacerbated by lungworm infection occurred in the controls after Day 24. Two died and repeated doses of antibiotic and anthelmintic therapy were necessary to save the remainder. Clinical signs were much milder in the ivermectin and OPRB groups and resolved with only a single dose of antibiotic. The OPRB group excreted some lungworm larvae at this time, but none was detected in the faeces of the ivermectin group during the grazing season. At housing, five calves from each group and four lungworm-naive calves were challenged with D. viviparus larvae. The infection became patent in all challenge-control calves, but no larvae were passed by any of the trial animals. Post-mortem worm-counts revealed percentage takes for the challenge controls, trial controls, ivermectin and OPRB groups of 16.7, 0.01, 0.9 and 0.2, respectively. All trial groups had therefore developed a substantial immunity. 相似文献
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1. Vigilance and feeding behaviour of male and female adult breeding ostriches were recorded to determine feeding and scanning bout lengths, a time budget and the pattern of vigilance immediately after food was provided. 2. Males were more vigilant and fed for shorter periods than females immediately after concentrate food was delivered but not throughout the whole day. 3. Most interscan periods of males were below 40 s with a maximum of 90 s compared with most interscan periods of females lasting less than 70 s with a maximum of 160 s. 4. Gender differences in behaviour are attributed to increased male vigilance for predators and/or conspecifics, and increased female feeding required for egg production and greater opportunity to feed because of male vigilance. 相似文献
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Abstract. The effectiveness of xylocaine anaesthesia, potentiated with sodium bicarbonate, was investigated on the altiplano cyprinid, Algansea lacustris Steindachner. The drug gave excellent sedation, handling and recovery and was effective at doses between 50 and 300 mg/l in 1 g/l sodium bicarbonate. 相似文献
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Complications and Long-term Results after Partial Laryngectomy for the Treatment of Idiopathic Laryngeal Paralysis in 45 Dogs 总被引:1,自引:0,他引:1
J. THOMAS ROSS dvm DAVID T. MATTHIESEN dvm Diplomate acvs KATHLEEN E. NOONE vmd Diplomate acvim THOMAS A. SCAVELLI dvm Diplomate acvs 《Veterinary surgery : VS》1991,20(3):169-173
Forty-five dogs with severe respiratory signs caused by idiopathic, acquired laryngeal paralysis were treated by partial laryngectomy. The predominant postoperative complications were coughing in 28 dogs and pneumonia in 15 dogs. Eight dogs required a second operation to alleviate persistent or recurrent upper airway obstruction. Results of surgery were considered excellent in 11 dogs (25%), good in 18 dogs (40%), fair in 6 dogs (13%), and poor in 10 dogs (22%). Poorer results were obtained by surgical residents than by more experienced surgeons. Death in the immediate postoperative period was related to pneumonia (8 dogs) and laryngeal collapse (1 dog). Nine dogs died later of respiratory disease. Although partial laryngectomy is effective for the treatment of laryngeal paralysis, it is not recommended because of the high incidence of postoperative complications. 相似文献