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1. The objective of this study was to investigate whether it is possible to reduce phosphorus (P) excretion by feeding a lower level of dietary P than that currently recommended, without compromising welfare, and whether this is sensitive to the level of dietary calcium (Ca). 2. A randomised complete block design was used with a total of 224 1-d-old male chicks of a commercial genotype in two batches. Chicks had a 10-d adaptation period. After this, they were moved to cages and allocated to one of 4 dietary treatments (4 and 3 birds per cage in batch 1 and 2, respectively). A standard level of Ca and P (8.3 and 6.6 g/kg, respectively) was compared with three lower levels of Ca (7.3, 6.3 and 5.3 g/kg) all at the same reduced level of P (5.5 g/kg). Records were made of live weight of birds on an individual basis and feed and water consumption on a cage basis. Every 7 d, the dry matter (DM) content of a sample of mixed excreta from each cage was measured. Birds were slaughtered and samples taken for analysis of plasma mineral content, retention of N, Ca and P and tibia bone strength. 3. The initial reduction in dietary mineral level did not adversely affect performance or bone strength. However, decreasing dietary Ca level below 7.3 g/kg, at constant P, led to reduced feed consumption and bone strength. Dietary treatment had no significant overall effect on water intake, water : feed ratio, excreta DM content, Ca and P retention or metabolisability of DM. There was no significant correlation between mean plasma Ca or P level and DM content of rectal digesta. 4. In conclusion, reducing dietary P from 6.6 to 5.5 g/kg to reduce potential environmental impact of broiler production had an adverse effect on bird welfare when the level of Ca was reduced below 7.3 g/kg, as a result of decreased feed intake in the early growth period and reduced skeletal strength.  相似文献   
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The total British area of limestone pavement is very small, yet this scarce resource is being destroyed to supply decorative stone. Its scientific interest is both geological and botanical. Exploiting an exhaustive survey, a weighted index was developed for assessing the conservation value of limestone pavements based on their deep grike floras. Using weighted indices, 27 sites in Cumbria, Gwynedd, Lancashire, North Yorkshire and Skye were identified as important for the conservation of limestone pavement floras.  相似文献   
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The Pacific oyster industry in Australia is derived from importations from Japan in the late 1940s and early 1950s to Tasmania and is almost completely hatchery based. This makes it a good target for developing and deploying genetically improved strains. An allozyme survey comparing hatchery stocks with self‐recruiting Tasmanian stocks and with two collections from Japan found abundant variation and no significant evidence of allele loss. The subsequent selection programme (initiated in the summer of 1996/97) had several strands. We wanted to take advantage of the increased power that marker‐assisted selection could bring and, therefore, needed to develop a linkage map and isolate flanking markers around quantitative trait loci (QTLs). Several types of markers (allozymes, microsatellites and AFLPs) were used, and single‐pair crosses were set up; QTLs have been detected. Conventional selection programmes, one based on mass selection and one on family selection, have been established. Triploid Pacific oysters produced via chemical means have been available for several years, but rates of triploidy achieved by such means are usually less than 100%. In 1999, we will assess whether our tetraploid 2‐year‐old broodstock can be crossed with diploids to give 100% triploid offspring.  相似文献   
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Deer are recognized as hosts of Mycobacterium bovis and assessing the role of wild cervids in perpetuating tuberculosis among cattle has motivated extensive research on several continents. In this paper, the histopathology of lymph node and lung tuberculous granulomas in M. bovis positive British deer is presented. The overall aim was to seek further insights into the potential for onward transmission from infected deer to other species, including cattle. Samples were obtained from an extensive survey of wild mammals in South-West England and from statutory tuberculosis surveillance. M. bovis culture-positive samples were characterised microscopically as to their stage of lesion advancement, number of acid-fast bacilli and granuloma encapsulation. Seventy percent of the deer developed granulomas containing far greater numbers of M. bovis bacilli than typically reported in cattle. Red and fallow deer had the largest number of poorly encapsulated granulomas often containing many hundreds of bacilli. The results are consistent with infected wild British deer being a potential source of environmental contamination and onward transmission to other species. However, further work on levels of bacillary shedding is required before this can be confirmed.  相似文献   
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A pure growth of Group Eugonic Fermenter-4 bacteria (gram-negative) was isolated from the lungs of an 11-year-old male domestic cat that had been ill for 2 days before death. Clinical signs included anorexia, severe dyspnea, and salivation. The lungs contained several firm, slightly raised, yellowish-gray, spherical nodules of various sizes. Purulent exudate was found in the pericardial sac and left pleural cavity. Histologic evaluation revealed multifocal suppurative pneumonia.  相似文献   
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Recovery of cows (n = 61) with mastitis caused by gram-negative bacteria and treated systemically with an antibiotic (gentamicin) to which the bacteria were susceptible in vitro, was compared with recovery of cows (n = 13) with similar infections treated with a systemically administered antibiotic (erythromycin) to which the bacteria were resistant in vitro or with recovery of cows (n = 12) not given an antibiotic systemically. In the first part of the study, cows were selected for treatment groups by use of a diagnostic scheme designed to predict whether the mastitis was caused by gram-negative or gram-positive bacteria. In the second part of the study, all cows were treated without systemic administration of an antibiotic. Significant difference was not observed in the outcome of the disease between cows given gentamicin and cows of the other 2 treatment groups at 24 hours or at 4 weeks after treatment. At 24 hours after initial treatment, 71.9% of cows treated with gentamicin, 92.3% of those treated with erythromycin, and 45.5% not treated systemically had improved appetite. At 4 weeks after initial treatment, of the cows treated with gentamicin, 11.5% died; in 32.8%, lactation ceased in the affected mammary gland; in 21.3%, lactation was decreased in the affected gland; and 34.4% returned to normal lactation and health. Of cows treated with erythromycin, none died; in 23%, lactation ceased in the affected mammary gland; in 23%, lactation decreased in the affected gland; and 54% returned to normal lactation and health.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
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