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1. Battery‐kept hens (Sykes Tints) showed a preference for a large (0.76 x 0.86 m) over a small (0.38 x 0.43 m) cage, but preferred the smaller cage when this had a litter floor to the one 4 times larger with a wire floor.

2. The hens still showed a preference for litter when they could obtain access to it only by entering an even smaller cage (0.38 x 0.215 m) in which they could hardly turn round. This cage gave far less space than that recommended by the UK Welfare Codes (1971).

3. The experiments described demonstrate that hens prefer larger to smaller cages and litter floors to wire ones, but that they give highest priority to flooring. Increasing the space allowed to battery‐kept hens may not therefore be as “valuable” to them as giving them access to litter.  相似文献   

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The commercial, welfare and environmental impacts of rearing small colonies of free-range chickens in newly planted woodland at two sites in the UK, during the first 2 years of the enterprise, were investigated. Newly planted rather than established trees were used so that commercially viable species could be planted in a way that would suit the management of the chicken enterprise, and small colonies were used so that farmers wishing to diversify could buy into the system progressively. It was anticipated that marketing a high specification product would provide an immediate income, whilst waiting for the future investment in trees to grow.  相似文献   
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Cucumber vein yellowing virus (CVYV) is emerging throughout the Mediterranean Basin, where it causes significant damage to cucumber and melon crops. It has been suggested that CVYV originated from the Middle East and has spread only recently to other areas. In this work, an isolate from Sudan was characterized, and surveys performed in that country between 1992 and 2012 revealed a long-term presence of CVYV with a high molecular variability, showing that the virus has long been endemic in sub-Saharan Africa. Comparison of the full-length sequences of 11 CVYV isolates from different geographic origins revealed recombination events in CVYV populations from the Mediterranean Basin and the Middle East, and evidence for different selection pressures along the genome. These results shed a new light on the evolution of CVYV.  相似文献   
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The purpose of this study was to determine whether bovine immunodeficiency virus (BIV) is vertically transmitted in naturally infected dairy cattle. Twenty-two dam/calf pairs from a Mississippi Agriculture and Forestry Experiment Station dairy were the study group. Blood samples were collected following delivery of calves, the peripheral blood leukocytes were purified from these samples, and the leukocyte DNA was used in polymerase chain reactions targeting the pol gene region of the BIV provirus. Southern blotting and hybridization were used to confirm the BIV specificity of the amplified fragments. BIV provirus was detected in 14 of 22 calves (64%), demonstrating vertical transmission. Eight of the calves were disqualified from the final interpretation of transplacental transfer because they may have nursed their mothers prior to blood collection, allowing the possibility of lactogenic transfer of the virus. Transplacental transmission of BIV was identified in 6 of 22 calves (27%).  相似文献   
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The frequency and etiology of ecdysial failures occurring during the pupal-adult transformation of the cotton boll weevil, Anthonomus grandis, was studied after treatment with juvenile hormone (JH) and/or diflubenzuron (DFB). Failure at emergence was the result of inability of the adult insects to escape from their pupal exuviae. Teratogenic effects in the form of pupal-adult intermediates or adults with pupal characters were not obtained with JH or DFB treatment after the larval-pupal ecdysis. Combining JH with the DFB treatment yielded a synergistic response that increased the frequency of ecdysial failures about sevenfold when applied in the later pupal stages. The fine structure of the abdominal cuticle of adults experiencing ecdysial failure after treatment with JH as white-eyed pupae exhibited granular deposits within the lamellar region and interference with deposition of the nonlamellate endocuticle. DFB treatment of the earlier pupal stages interfered with deposition of the lamellate cuticle by eliminating or reducing the lamellar structure. It was concluded that the primary interaction of JH with DFB was that of extending or reinitiating DFB sensitivity in the later pharate adult. A secondary interaction may involve inhibition of cuticle hardening as both JH and DFB appear to inhibit the tanning process of adults treated as white-eyed pupae.  相似文献   
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This article analyzes learning in context through the prism of a sustainable dairy-farming project. The research was performed within a nutrient management project that involved the participation of farmers and scientists. Differences between heterogeneous forms of farmers knowledge and scientific knowledge were discursively constructed during conflict and subsequent alignment over the validity and relevance of knowledge. Both conflict and alignment appeared to be essential for learning in context. Conflict spurred learning when disagreeing groups of actors developed their knowledge in order to strengthen their arguments. Conflict caused self-referentiality when the actors no longer listened to each other. This inhibited self-reflection, thus blocking ongoing learning. Nevertheless, after a period of alignment, scientific models and knowledge of farmers were reevaluated and recontextualized. Through determining how to use scientific models and farmers knowledge for further learning, aimed at a shared goal, the participating actors also learned how to learn.Jasper Eshuis is a PhD candidate in the Department of Communication Management at Wageningen University, The Netherlands. His research deals with multiple land use, governance processes, and farmers decision-making. He is currently interested in monitoring and trust.Marian Stuiver is a PhD candidate in the Department of Rural Sociology of Wageningen University, The Netherlands. Her current research focuses on nutrient management, farmers innovation, and co-production of knowledge within the agricultural sciences.  相似文献   
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