Modeling the Exchanges of Energy, Water, and Carbon Between Continents and the Atmosphere

Atmospheric general circulation models used for climate simulation and weather forecasting require the fluxes of radiation, heat, water vapor, and momentum across the land-atmosphere interface to be specified. These fluxes are calculated by submodels called land surface parameterizations. Over the last 20 years, these parameterizations have evolved from simple, unrealistic schemes into credible representations of the global soil-vegetation-atmosphere transfer system as advances in plant physiological and hydrological research, advances in satellite data interpretation, and the results of large-scale field experiments have been exploited. Some modern schemes incorporate biogeochemical and ecological knowledge and, when coupled with advanced climate and ocean models, will be capable of modeling the biological and physical responses of the Earth system to global change, for example, increasing atmospheric carbon dioxide.     

Circulating Metabolic Hormones During the Peripubertal Period and Their Association with Testicular Development in Bulls

The objective of the present study was to characterize changes in serum metabolic hormones concentrations from 20 weeks before to 20 weeks post-puberty in bulls and to investigate the associations of metabolic hormones concentrations with testicular development. Leptin concentrations increased from 16 weeks before puberty to 8 weeks post-puberty and insulin concentrations increased from puberty to 8 weeks post-puberty. Growth hormone concentrations decreased after 4 weeks post-puberty, whereas IGF-I concentrations increased from 8 weeks before puberty to 8 weeks post-puberty. During this period, testicular growth was accelerated and testosterone secretion increased substantially, without any significant changes in gonadotropin secretion. Monthly circulating concentrations of leptin, IGF-I and insulin accounted for 63% of the variation in scrotal circumference and 59% of the variation in paired testes volume. In conclusion, the secretion of metabolic hormones was not associated with changes in gonadotropins concentrations. Furthermore, the associations of leptin, IGF-I and insulin concentrations with testes size indicated that these hormones might be involved in a gonadotropin-independent mechanism regulating the testicular development in peripubertal bulls.     

Effect of breed of cattle on innate resistance to infection with <i>Babesia bovis, B bigemina and Anaplasma marginale

Objective To assess the innate resistance of naive Bos taurus, Bos taurus cross Bos indicus and Bos indicus cattle to virulent Babesia bovis, B bigemina and Anaplasma marginale parasites. Design Groups of 10, pure B indicus, fi B indicus cross,/B indicus cross and pure B taurus steers were infected with virulent B bovis, B bigemina and A marginale parasites. Procedure Sequential infections were carried out by intravenous inoculation of infected blood containing 1 times 10⁸ parasites of B bovis, followed by B bigemina and then A marginale. To assess resistance, measurements were made of parasitaemia, rectal temperature, packed cell volume and the number within a group requiring chemotherapy to control infection. There was a recovery period between each infection. Results Infection with B bovis showed that pure B indicus steers were significantly more resistant to B bovis infection than the other groups, with none of this group requiring treatment. There was no significant difference between fi B indicus cross and/B indicus cross with 30% and 20%, respectively, of steers in these groups requiring treatment. The pure B taurus steers were significantly more affected then those in the other three groups with 80% requiring treatment. Infections of B bigemina produced a mild response in comparison to that of B bovis and none of the steers required treatment. However, the pure B taurus group was significantly more affected than the other three groups for all other measurements. After the A marginale infection, B indicus steers were moderately affected with 50% requiring treatment, whereas 70% of the fi B indicus group, 80% of the /B indicus cross group and 100% of the pure B taurus group required treatment. Conclusions All breeds of cattle, ranging from pure B indicus to pure B taurus may be at risk of severe disease if exposed to virulent A marginale. The results confirm that pure B indicus cattle are relatively resistant to B bovis, but there could be a significant risk of severe mortalities if cross-bred herds are exposed to virulent infection.     

马家塔露天矿生态复垦区土壤养分状况研究

本文系统研究了神东矿区马家塔露天采坑复垦区土壤养分状况,结果显示:复垦区土壤基本上为原始回填土,剖面层次不发育,成土程度很低;土壤机械组成以砾石、粗沙为主,含量高达90%。有机质、含碱解氮含量略高于未受扰动的原状土壤,但速磷、速钾含量均低于原状土壤,总体评价土壤属于养分贫乏型;成土程度低、养分含量少是农林业生产水平不高的主要原因。研究表明通过改良复垦工艺以及提高复垦区生产管理水平是提高土地生产力的主要措施。     

Ultrastructure of hepatic and renal lesions in chickens fed aflatoxin

Male broiler chicks were given feed and water ad libitum from hatching through 3 weeks of age. The feed contained 0, 1.25, 2.5, and 5.0 micrograms of aflatoxin/g of feed. The chicks were killed by cervical dislocation and specimens of liver and kidney were obtained for electron microscopy on days 3, 6, 9, 17, and 21. In chicks fed 5.0 micrograms of aflatoxin, the primary lesions in liver were hepatocellular lipidosis, enlargement of bile canaliculi, reduction in mitochondrial size, mild lymphocytic infiltration, and hepatocellular degeneration and necrosis. Similar lesions were noticed in some chicks fed 2.5 micrograms of aflatoxin, but none was observed in chicks fed at 1.25 micrograms of aflatoxin. At 5 micrograms of aflatoxin, the most consistent lesion in the kidney was thickening of the glomerular basement membrane. Similar glomerular lesions were observed at 2.5 micrograms of aflatoxin, but not at 1.25 micrograms of aflatoxin. Some foot processes of the glomerular epithelial cells were poorly developed. Fusion of foot processes was not observed and fibrous material was not evident in the basement membrane. The pseudopodia of endothelial cells lining the thickened basement membrane were depleted in number or were absent. Degenerative changes also were observed in the cells of the proximal convoluted tubules, but these were less consistent than those of the glomerulus.     

Myxomatosis of the Depilated Angora rabbit. A Preliminary Study

Abstract— A nodular eruption occurring on the skin of depilated Angora rabbits was studied at 47 rabbit farms in 1988. Virus isolation, electron microscopy, transmission experiments and comparison with experimental infection using recognised strains of myxoma virus confirmed that the disease was myxomatosis. The disease occurred particularly in July and August in rabbits vaccinated in March or April with the heterologous vaccine. Morbidity on farms where lesions occurred only on depilated skin was much lower than on those where generalised forms occurred. In experimental intradermal infections of unvaccinated New Zealand White rabbits, both primary and secondary myxomas occurred earlier in inoculated animals depilated up to five days before or on the day of inoculation; but after six days development of lesions in the depilated area was not observed. The authors advance the hypotheses that the nature ot the spontaneous disease in rabbitries is dependant on the residual level of post-vaccinal immunity. Where this is high, myxomatosis does not occur. Where it is low classical myxomatosis, with numerous lesions on the depilated skin, occurs. Intermediate levels of immunity are able to restrict the development of myxomas to the depilated area. Résumé— Des nodules cutanés, se développant exclusivement sur le dos de quelques animaux récemment épilés, ont été observés en 1988 dans 47 élevages de lapins angora. L'isolement viral, la microscopie électronique, la transmission expérimentale et la comparaison avec l'infection expérimentale par des souches de virus myxomateux ont permis de montrer qu'il s'agissait d'une forme particulière de myxomatose. La maladie était principalement observée en juillet et août sur des lapins vaccinés en mars et avril avec un vaccin hétérologue. La morbidité dans les élevages atteins était significativement inférieure à celle constatée dans les élevages affectés par des formes classiques de myxomatose. L'infection expérimentale de lapins néo-zélandais non vaccinés a montré que le développement des myxomes était plus précoce lorsque les animaux étaient épilés cinq jours avant ou le jour de l'inoculation; mais aucune lésion ne fut observée dans la zone épilée lorsque l'épilation avait lieu plus de six jours après l'inoculation. Les auteurs émettent l'hypothèse que l'aspect de la maladie dépend du niveau résiduel de l'immunité post-vaccinale. Si ce niveau est élevé, la maladie n'apparaît pas. S'il est insuffisant, on observe une forme classique de myxomatose, avec en plus de nombreux myxomes dans la zone cutanée épilée. Une immunité intermédiaire limite le développement des myxomes aux zones cutanées épilées. Zusammenfassung— Das Auftreten von Nodula auf der Haut von enthaarten Angorakaninchen wurde 1988 in 47 Kaninchenfarmen untersucht. Durch Virusisolierung, elektronenmikroskopische Untersuchungen, Übertragungsversuche und den Vergleich mit experimentellen Infektionen mit bekannten Myxomavirusstämmen konnte bestätigt werden, daß es sich bei der Erkrankung urn Myxomatose handelte. Die Ekrankung trat vor allem im Juli und August bei Kaninchen auf, die im März oder April mit heterologen Vakzinen geimpft worden waren. Die Morbidität in Betrieben, wo die Veränderungen nur auf enthaarter Haut auftraten, war viel niedriger als bei denen, wo generalisierte Formen auftraten. Bei experimentellen intradermalen Infektionen nicht geimpfter Weiße Neuseeland-Kaninchen traten sowohl primäre wie sekundäre Myxome früher auf bei den inokulierten Tieren, die bis zu fünf Tage vor der Inokulation depiliert worden waren; 6 Tage danach jedoch wurde keine Entwicklung von Veränderungen im depilierton Bereich festgestellt. Die Autoren stellen die Hypothese auf, daß der Grad der natürlichen Erkrankung in Kaninchenhaltungen von dom residualen Spiegel der durch Impfung erzeugten Immunität abhängt. Wo dieser Spiegel hoch ist, tritt die Myxomatose nicht auf. Wo er niedrig ist, kommt es zu der klassischen Myxomatose mit zahlreichen Veränderungen auf der enthaarten Haut. Mittlere Immunitätsspiegel können die Entwicklung der Myxome of enthaarte Gebiete beschränken. Resumen Una erupción nodular producida en la piel de conejos de Angora depilados fue estudiada en 47 granjas de conejos en 1988. El aislamiento de virus, microscopía electrónica, experimentos de transmisión y la comparación con infecciones experimentales usando cultivos conocidos del virus myxoma, confirmaron que la enfermedad era myxomatosis. La enfermedad ocurrió especialmente en julio y agosto en conejos vacunados en marzo o abril con la vacuna heteróloga. En infecciones experimentales intradérmicas de conejos no vacunados New Zealand y Blancos, ambos myxomas, primario y secundario ocurrieron más pronto en animales inoculados depilados hasta unos cinco dias antes o en el día de la inoculacion; pero después de seis días no se observó desarrollo de lesiones en el area depilada. Los autores avanzaron la hipotesis de que la naturaleza de la enfermedad espontánea en rabbitrios es dependiente del nivel residual de inmunidad post-vacunal. Dónde este es elevado no se produce myxomatosis. Dónde es bajo, se produce la clásica myxomatosis con numerosas lesiones en la piel depilada. Niveles intermedios de inmunidad son capaces de restringir el desarrollo de myxomas en el area depilada.     

A survey of cattle producers in the Boophilus microplus endemic area of Queensland to determine attitudes to the control of and vaccination against tick fever

SUMMARY: A survey by mail was used to determine the views of beef producers in the Boophilus microplus endemic area of Queensland on the control of and vaccination against tick fever. Data from 448 questionnaires were analysed, representing 2.7% of beef producers in the survey area. Producers considered buffalo fly ( Haematobia irritans exigua ) infestation as the most important problem whereas tick fever ranked sixth overall. Private veterinarians were regarded as the most important source of information on vaccines for cattle followed by a weekly rural newspaper. From the survey we estimate that about 33% of producers used the tick fever vaccine produced by the Tick Fever Research Centre of Queensland Department of Primary Industries but there were significant (P < 0.05) variations between regions and herds. Large herds (≥ 400 head) in south-east Queensland were the most likely to be vaccinated against tick fever. Of the producers who did not use the vaccine, over 70% replied that there was no need to vaccinate because of the low risk of the disease in their herds. In 52% of unvaccinated herds the treatment of animals with acaricide was considered the most important means of tick fever control and 61% of these herds comprised Bos indicus x Bos taurus or Bos indicus cattle.