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21.
Intensive broiler (meat) chicken production now exceeds 800 million birds each year in the United Kingdom and 2 x 10(10) birds worldwide, but it attracts accusations of poor welfare. The European Union is currently adopting standards for broilers aimed at a chief welfare concern--namely, overcrowding--by limiting maximum 'stocking density' (bird weight per unit area). It is not clear, however, whether this will genuinely improve bird welfare because evidence is contradictory. Here we report on broiler welfare in relation to the European Union proposals through a large-scale study (2.7 million birds) with the unprecedented cooperation of ten major broiler producers in an experimental manipulation of stocking density under a range of commercial conditions. Producer companies stocked birds to five different final densities, but otherwise followed company practice, which we recorded in addition to temperature, humidity, litter and air quality. We assessed welfare through mortality, physiology, behaviour and health, with an emphasis on leg health and walking ability. Our results show that differences among producers in the environment that they provide for chickens have more impact on welfare than has stocking density itself. 相似文献
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Structural basis of quantitative variation in nuclear DNA 总被引:3,自引:0,他引:3
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Speer RJ Garton WR Morgan JF Nicholls RW Goldberg L Parkinson WH Reeves EM Jones TJ Paxton HJ Shenton DB Wilson R 《Nature》1970,226(5242):249-250
Flash spectra of the total solar eclipse throughout all its phases have been obtained in the extreme ultraviolet for the first time. 相似文献
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Animal societies are stages for both conflict and cooperation. Reproduction is often monopolized by one or a few individuals who behave aggressively to prevent subordinates from reproducing (for example, naked mole-rats, wasps and ants). Here we report an unusual mechanism by which the dominant individual maintains reproductive control. In the queenless ant Dinoponera quadriceps, only the alpha female reproduces. If the alpha is challenged by another female she chemically marks the pretender who is then punished by low-ranking females. This cooperation between alpha and low-rankers allows the alpha to inflict punishment indirectly, thereby maintaining her reproductive primacy without having to fight. 相似文献
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Hon WC Wilson MI Harlos K Claridge TD Schofield CJ Pugh CW Maxwell PH Ratcliffe PJ Stuart DI Jones EY 《Nature》2002,417(6892):975-978