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The influence of sex-linked dwarf (dw) and incompletely dominant frizzle (F) genes on growth, egg production and quality were investigated. The experimental stock comprised 100 chicks of four genotypes: normal feathered, normal size (ffDw); normal feathered, dwarf (ffdw); frizzle, normal size (FfDw); and frizzle, dwarf (Ffdw). The dwarf gene reduced the body weight, shank length, feed intake, egg production and egg weight. The frizzle gene also reduced most of these traits, except for egg production, the interaction between the two genes being positive only for growth traits and egg number. Neither of the two genes significantly influenced egg quality. It was concluded that the dwarf gene may have some practical interest in tropical environments, while more needs to be known about the frizzle gene. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
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Tropical Animal Health and Production - This study was conducted to determine intake and growth performance of broiler chicks fed with Jatropha curcas kernel meal physico-chemically and...  相似文献   
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Viable biocontrol agents for mosquito control are quite rare, therefore improving the efficacy of existing biological agents is an important study. We need to have a better understanding of the predation-risk behavioral responses toward prey. This research examined prey choices by Toxorhynchites splendens by monitoring the behavioral responses of Aedes aegypti, Aedes albopictus, and Anopheles sinensis larvae when exposed to the predator. The results show that Tx. splendens prefers to consume Ae. aegypti larvae. The larvae exhibited different behavioral responses when Tx. splendens was present which suggest vulnerability in the presence of predators. “Thrashing” and “browsing” activities were greater in Ae. aegypti larvae. Such active and risky movements could cause vulnerability for the Ae. aegypti larvae due to increasing of water disturbance. In contrast, Ae. albopictus and An. sinensis larvae exhibited passive, low-risk behaviors, spending most of the time on the “wall” position near the edges of the container. We postulated that Ae. aegypti has less ability to perceive cues from predation and could not successfully alter its behavior to reduce risk of predation risk compared with Ae. albopictus and An. sinensis. Our results suggest that Tx. splendens is a suitable biocontrol agent in controlling dengue hemorrhagic vector, Ae. aegypti.  相似文献   
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The objective of this study was to assess the reliability of pot-based screening method for iron (Fe) toxicity tolerance in rice using soils from hot spots. Five lowland rice varieties with known reaction to Fe toxicity were grown in pots in a screen house for three seasons. Fe-toxic soils from two hot spot fields – Edozighi, Nigeria and Niaouli, Benin were used and soil from Africa Rice Center (AfricaRice) experimental farm, Cotonou, Benin was included as control. Leaf bronzing score (LBS) was determined at different stages, and grain yield was determined at maturity. Heritability was estimated using data across the three seasons. High heritability was recorded for LBS and grain yield. Grain yield reduction in stress treatment relative to control varied from 15 to 56% depending on the variety and soil. Bao Thai, Suakoko 8, and WITA 4 had better performance under Fe toxicity in terms of LBS, yield and relative yield reduction, whereas Bouake 189 and IR64 had poorer performance. Grain yield and LBS were significantly correlated but negatively at 60 days after sowing (DAS). Overall, the results found in this experiment were consistent with previous field studies. Therefore, pot screening using soils from hot spots can be used by rice breeding programs to reliably assess Fe toxicity tolerance ex situ.  相似文献   
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Oedaleus senegalensis is a serious pest of millet in the Sahel, but the correlation to crop loss remains largely unknown. Therefore, the correlation between densities of O. senegalensis, defoliation level and millet yields was investigated in Niger in 2008, and a simple model to foresee the yield based on these parameters was developed. The yield was significantly correlated to both the density of O. senegalensis and the defoliation level on 17 September. The best model to foresee millet yield involved grasshopper density and cumulated rainfall and may be regarded a tentative method in O. senegalensis control.  相似文献   
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The hypocholesterolemic effect of dietary proteins could not be related to their vegetal or animal origin and seemed correlated to their different amino acids proportions. Comparing rats fed soy protein diet to those fed casein diet for 45 days, we observed a decrease of serum HDL cholesterol levels. Furthermore sequential centrifugation showed a decrease of HDL2–3 fraction and especially apolipoprotein E in the serum of soy protein fed rats. The sodium phytate, added to the diet, did not change the metabolism of sterols.  相似文献   
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While weeds generally are considered as the most important overarching production constraints in inland‐valley cropping systems in West Africa, little is known about species' associations with environmental and crop management factors. Weed species' associations with seasonal and environmental factors, such as their position on the catena, soils and cropping systems, were studied during two seasons (dry and wet) in 45 arable fields of three inland valleys in south‐western Benin, Africa. The three most dominant weed species were Dactyloctenium aegyptium, Commelina benghalensis and Digitaria horizontalis on the inland‐valley crests (uplands), Ludwigia hyssopifolia, Corchorus aestuans and Ludwigia octovalvis on the sloping hydromorphic fringes and Leersia hexandra, Ipomoea aquatica and Fimbristylis ferruginea in the valley bottoms (lowlands). Echinochloa colona, Cleome viscosa and Talinum triangulare were the three most dominant species in the dry‐season crops (maize or vegetables) and Leer. hexandra, I. aquatica and Sphenoclea zeylanica were the three most dominant species in the wet‐season crop (rice). Ageratum conyzoides, Synedrella nodiflora and D. horizontalis were observed throughout the catena. Problem weeds in inland‐valley agro‐ecosystems are those that combine a high frequency with a high submergence tolerance and ecological plasticity, C4 grasses, perennial C3 species with persistent root structures and broad‐leaved species with high propagation rates. Weed management strategies that are aimed at increasing the resilience of rice‐based cropping systems in the inland valleys of the southern Guinea Savanna of Africa should address the categories of problem species that were identified in this study. This can be done best by following an integrated approach, including the use of more weed‐competitive cultivars and rotation crops.  相似文献   
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The demand for rice in Eastern and Southern Africa is rapidly increasing because of changes in consumer preferences and urbanization. However, local rice production lags behind consumption, mainly due to low yield levels. In order to set priorities for research and development aimed at improving rice productivity, there is a need to characterize the rice production environments, to quantify rice yield gaps—that is, the difference between average on-farm yield and the best farmers’ yield—and to identify causes of yield gaps. Such information will help identifying and targeting technologies to alleviate the main constraints, and consequently to reduce existing yield gaps. Yield gap surveys were conducted on 357 rice farms at eight sites (19–50 farmers per site) across five rice-producing countries in Eastern and Southern Africa—that is Ethiopia, Madagascar, Rwanda, Tanzania and Uganda—for one or two years (2012–13) to collect both quantitative and qualitative data at field and farm level. Average farm yields measured at the eight sites ranged from 1.8 to 4.3 t/ha and the average yield gap ranged from 0.8 to 3.4 t/ha. Across rice-growing environments, major causes for yield variability were straw management, weeding frequency, growth duration of the variety, weed cover, fertilizer (mineral and organic) application frequency, levelling and iron toxicity. Land levelling increased the yield by 0.74 t/ha, bird control increased the yield by 1.44 t/ha, and sub-optimal management of weeds reduced the yield by 3.6 to 4.4 t/ha. There is great potential to reduce the current rice yield gap in ESA, by focusing on improvements of those crop management practices that address the main site-specific causes for sub-optimal yields.  相似文献   
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There are few studies of community growth promotion as a means of addressing malnutrition that are based on longitudinal analysis of large-scale programmes with adequate controls to construct a counterfactual. The current study uses a difference in difference comparison of cohorts to assess the impact on the proportion of underweight children who lived in villages receiving services provided by the Senegal Nutrition Enhancement Project between 2004 and 2006. The project, designed to extend nutrition and growth promotion intervention into rural areas through non-governmental organisation service providers, significantly lowered the risk of a child having a weight more than 2 sd below international norms. The odds ratio of being underweight for children in programme villages after introduction of the intervention was 0.83 (95% CI 0.686, 1.000), after controlling for regional trends and village and household characteristics. Most measured aspects of health care and health seeking behaviour improved in the treatment relative to the control.  相似文献   
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