Nonchromosomal genes: extrachromosomal elements in lower eukaryotes     

Blackburn EH 《Science (New York, N.Y.)》1987,237(4812):307

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Viviparity and testability     

Blackburn DG 《Science (New York, N.Y.)》1988,241(4864):399

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The shape of the response curve relating protein intake to egg output for flocks of laying hens     

T. R. Morris  Qhazel A. Blackburn 《British poultry science》1982,23(5):405-424

1. Two experiments were conducted to test the hypothesis that, as dietary protein concentration is increased, increments of response gradually diminish as egg output approaches an asymptotic value; and that the resulting response curve is consistent with a model (the “Reading model”) which assumes that the shape of the curve is a function of individual variation in body weight and potential egg output.

2. Each experiment involved a total of 3 888 laying pullets. Nine diets, with crude protein contents ranging from 87 to 212 g/kg, were used in the first experiment and ten diets, with protein contents ranging from 81 to 215 g/kg, in the second experiment. Diets were denned in terms of their calculated contents of essential amino acids and the same, well‐balanced amino acid profile was used at all protein contents within one experiment. Supplementary experiments were conducted to identify the limiting amino acid (s) in the experimental diets.

3. Treatments were applied for ten weeks, starting at 30 or 32 weeks of age. Average egg output on the highest protein diets was 57.0 g/bird d in the first experiment, which used White Leghorn pullets, and 53.7 g/bird d in the second experiment, which used a crossbred brown‐egg stock.

4. The response curves obtained showed diminishing returns and, in the second experiment, a clear plateau was reached. The Reading model was fitted and compared with a two‐straight‐line model and with curves derived from quadratic and inverse polynomial equations. Only the Reading model proved satisfactory for the interpretation of the data, as judged by goodness of fit and estimation of the optimum amino acid input. Although alternative models may provide a good fit when dealing with a single set of data, none of the alternatives is consistently satisfactory when considering the results of more than one experiment.  相似文献   

Factors in disease: a project summarized     

Blackburn H 《Science (New York, N.Y.)》1981,214(4520):549-550

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Interactions between different media and follicle‐stimulating hormone supplementation on in vitro culture of preantral follicles enclosed in ovarian tissue derived from collared peccaries (Pecari tajacu Linneaus, 1758)          下载免费PDF全文

GL Lima  VB Luz  LF Lima  RMP Rocha  SV Castro  TS Castelo  APR Rodrigues  JR Figueiredo  AR Silva 《Reproduction in domestic animals》2018,53(4):880-888

The aim was to verify the effect of follicle‐stimulating hormone (FSH) supplementation to α‐MEM+ or TCM199+ media on the in vitro development of ovarian preantral follicles (PFs) derived from collared peccaries. Ovaries (n = 5 pairs) were collected and divided into fragments destined to control group (non‐cultured) or treatments that were cultured for 7 days. The PFs morphology, growth and activation were evaluated by classical histology. The immunohistochemistry markers Ag‐NOR and PCNA were used for nuclear proliferation analysis, and the picrosirius red labelling was used for ovarian extracellular matrix (ECM) evaluation. After 7‐day culture, only the TCM199+ treatment maintained the proportion of intact PFs similar to day 1 (63.2%), but no differences were found among treatments (p > .05). In addition, a significant increase in the growing follicles proportion was verified for all the treatments, indicating follicular activation (p > .05). By the Ag‐NOR analysis, only the TCM199+/FSH maintained the nuclear proliferation similar to the first day (p > .05). The picrosirius red staining revealed that the ECM remained intact in all the treatments (p > .05). We suggest the use of TCM199+ medium supplemented of FSH for the in vitro development of peccaries PFs under 7‐day culturing conditions.  相似文献   

Validation of the periodicity of growth zone formation in the otoliths of four fish species from the Upper Zambezi ecoregion,southern Africa     

Geraldine C Taylor  Richard A Peel  Clinton J Hay  Olaf LF Weyl 《African Zoology》2016,51(3):153-159

In the Upper Zambezi and Okavango ecoregions, Brycinus lateralis, Hepsetus cuvieri, Schilbe intermedius and Serranochromis macrocephalus are important in subsistence fisheries, while S. intermedius and S. macrocephalus are often caught in commercial catches. Despite their importance, there is little information on their age and growth and age validation. Growth zone deposition rate in otoliths of B. lateralis, H. cuvieri, S. intermedius and S. macrocephalus was validated as annual using edge analysis in this study. Annual deposition of growth zones was corroborated by a fluorochrome marking experiment. Both methods demonstrated that one growth zone was deposited annually. Edge analysis demonstrated that the highest proportion of opaque zones was detected between August and December, most likely as a result of slow growth during lower temperature water during the preceding winter. With growth zone deposition validated as annual, future research should focus on determining the growth, maturity and mortality rates of these species, parameters which are important for their management.  相似文献   

Prevalence of odontoclastic resorptive lesions in a population of clinically healthy cats     

Ingham KE  Gorrel C  Blackburn J  Farnsworth W 《The Journal of small animal practice》2001,42(9):439-443

The prevalence of odontoclastic resorptive lesions (ORLs) was determined in a clinically healthy cat population (228 cats) using both clinical (oral examination) and radiographic (full-mouth series with intraorally positioned dental film) methods. The overall prevalence rate was 29 per cent (mean age of the cat population 4.9 years). The mandibular third premolars (307, 407) were the most commonly affected tooth and the pattern of ORL development was symmetrical in most cats. The risk of having ORLs was found to increase with increasing age and cats with clinically and radiographically missing teeth were more likely to have the condition. Neutering, gender, age at neutering or mean whole mouth gingivitis index did not affect the prevalence of ORLs.  相似文献   

Effects of a high-protein, low-energy diet in finishing lambs: 2. Weight change, organ mass, body composition, carcass traits, fatty acid composition of lean and adipose tissue, and taste panel evaluation     

W. Pittroff  D.H. Keisler  H.D. Blackburn 《Livestock Science》2006,101(1-3):278-293

An experiment was conducted to evaluate the effects of a high protein – low energy diet on body composition of feedlot lambs The objective was to assess the capability of such a diet to reduce body fat while preserving lean body mass. Three dietary regimens were compared: a typical feedlot diet (CON), barley straw at libitum (STR), and barley straw supplemented with fish meal (SFM). The latter two diets caused an energy deficit in the experimental animals. Significant treatment effects on mass of metabolic organs, body composition, and carcass data were observed. Conventional analysis of sensory data and fatty acid profiles of adipose and muscle tissue identified few significant dietary effects, yet discriminant analysis clearly separated all treatment groups. It was concluded that protein supplementation of ruminants in the catabolic state does not conserve protein mass. Given the high cost of protein supplementation, the post hoc modification of body composition of feedlot lambs is not a viable option. It is suggested that the production of feedlot lambs with a desirable degree of fatness should employ a feeding strategy dynamically adapted to the changes in protein – energy balance required by the growing ruminant.  相似文献   

Current distribution of sarcoptic mange in wombats   总被引：2，自引：0，他引：2  

RW MARTIN  KA HANDASYDE  LF SKERRATT 《Australian veterinary journal》1998,76(6):411-414

Objective To determine the distribution and prevalence of sarcoptic mange in wombats, particularly the common wombat ( Vombatus ursinus ).
Design Questionnaire survey in two parts.
Procedure Questionnaires were distributed to biologists, rangers, animal carers and naturalists. Part 1 of the questionnaire aimed to determine the present distribution of sarcoptic mange in wombats (103 responses). Part 2 invited respondents to assess the prevalence of sarcoptic mange in wombats over a 3 month period (four responses). Information on wombats from 66 localities was received. Each locality represented an area of about 2500 km².
Results Mange was observed at 93% of localities surveyed and Sarcoptes scabiei was present in common wombats at 52% of localities. Sarcoptic mange was highly prevalent (22%) in two common wombat populations in Victoria. Anecdotal evidence suggested that mange epizootics are sporadic, cause significant morbidity and mortality and have a substantial effect on local abundance. The respondents did not report sarcoptic mange in either northern hairy-nosed wombats ( Lasiorhinus krefftii ) or southern hairy-nosed wombats ( Lasiorhinus latifrons ).
Conclusions Sarcoptic mange occurs in common wombat populations throughout the range of the common wombat including Tasmania and Flinders Island. While mange epizootics are sporadic, they have the potential to threaten the long-term survival of small, remnant populations.  相似文献   

Stem respiration in leafy cuttings of Prosopis juliflora during the rooting process     

J. McP. Dick  D. G. Blackburn  C. McBeath 《New Forests》1994,8(2):179-184

An oxygen electrode was used to estimate the respiration rate of basal 1 cm sections of Prosopis juliflora cuttings. The respiration rate per unit dry mass decreased linearly with increasing diameter at a rate of 0.42 nmol0₂g^–1s^–1mm^–1 between the range of 1–3 mm diameter. However, as a result of increased mass, total respiration for the whole 1 cm section of tissue increased linearly with increasing diameter. The average respiration rate of the basal 1 cm of stem tissue, measured 14 days after insertion in the propagator, was almost double that of the 1 cm section of tissue above it (1.01 nmol0₂g^–1s^–1 compared to 0.57 nmol0₂g^–1s^–1). The value of this technique as an aid to our understanding of the development of adventitious roots is discussed.  相似文献