The structure, dynamics and movement patterns of the Australian sheep industry     

East IJ  Foreman I 《Australian veterinary journal》2011,89(12):477-489

Objective To describe the structure of Australia's sheep industries and the movement of sheep to enable examination of the potential for animal movements to spread disease between farms. Procedure The structure, size, marketing and movement patterns of Australian sheep farms was determined through (i) review of data published by the Australian Bureau of Statistics and Australian Bureau of Agricultural and Resource Economics, (ii) interviews with producers and saleyard managers and (iii) expert opinion. Results Twelve geographic regions are described, based on the type and extent of sheep farming in each region. Five production sectors were identified within the Australian sheep industry, with the proportion of each varying between the geographic regions. Over the past 20 years, the industry has decreased in size and contracted from the northern and central areas of Australia. Movement of sheep onto the majority (79%) of properties was limited to the introduction of less than 50 stud rams annually, although cross‐bred‐ and wether‐based farms introduced up to 2000 sheep annually; 75% of sheep movements occurred over distances less than 200 km, but stud rams moved up to 500 km. An increasing percentage of movements off farms was direct to abattoirs and over 80% of sheep sold through saleyards were purchased by abattoirs. Conclusions The majority of Australian sheep farms operate as self‐replacing enterprises and introduce few stock. In addition, most sheep movements occur over distances of less than 200 km and therefore sheep movements within Australia have only a limited potential to spread disease over larger distances.  相似文献   

A natural infection of sheep with Ostertagia ostertagi     

MG O''CALLAGHAN  RR MARTIN  IJ McFARLAND 《Australian veterinary journal》1992,69(1):19-20

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Risk factors associated with mastitis in dairy goats     

N E East  E F Birnie  T B Farver 《American journal of veterinary research》1987,48(5):776-779

Prevalence of intramammary infection in healthy goats was determined from 4,662 composite udder samples taken over a 9-month period. For each doe, a colostral sample and 2 milk samples were collected. Breed, age, number of days not lactating before kidding, number of lactation days, and kidding date were recorded. Coagulase-negative Staphylococcus spp were isolated from 17.5% of does, Staphylococcus aureus from 3.1%, Mycoplasma spp from 1.2%, Streptococcus spp from 0.3%, and gram-negative bacteria from 2.0%. Gram-negative organisms were associated with intermittent infections, whereas coagulase-negative staphylococci were associated with persistent infections. Intramammary infection was related to breed, number of days not lactating, and number of lactation days, as determined by log-linear analysis. Does of the Nubian breed, does with nonlactating periods of greater than 60 days, and does in the first and last third of a standard 305-day lactation appeared to be at higher risk for intramammary infection.  相似文献   

湿地松多效益经营模式林分采伐技术研究     

王青春孙海放  吴从健彭倚云 《林业研究》2004,15(1):69-72,J003

在利用Richards函数对湿地松生长进行拟合和利用动态规划方法在计算机上直接模拟抚育间伐的基础上，初步确定了江西省丘陵区湿地松多效益经营模式林分的采伐技术。研究结果表明：湿地松多效益经营模式林分始伐年龄为8．10年，主伐年龄为25年，最优抚育间伐方案为间伐3次(含始伐)，时间分别为第8、12及16年，间伐强度分别为每公顷950、700、300株，最后保留株数为每公顷550株。表2参7。  相似文献   

A serological and virological survey for evidence of infection with Newcastle disease virus in Australian chicken farms     

Kite VG  Boyle DB  Heine HG  Pritchard I  Garner MG  East IJ 《Australian veterinary journal》2007,85(6):236-242

OBJECTIVE: To determine the prevalence and distribution of antibodies to Newcastle disease virus on Australian chicken farms and to determine the pathotype and relationships of the Newcastle disease viruses present on those farms. DESIGN: A cross-sectional survey of 753 commercial chicken farms. PROCEDURE: The survey comprised a detailed questionnaire and collection of venous blood samples. The titre of antibodies to Newcastle disease virus was determined by haemagglutination inhibition. Virus isolation was conducted from cloacal and tracheal swabs taken from chickens in serologically positive flocks. Virus isolates were pathotyped on the basis of the deduced Fusion protein cleavage site determined by nucleotide sequencing of a 265 bp region of the genome in the region of the cleavage site. RESULTS: Antibody evidence of Newcastle disease virus infection was found on 300 of the 753 surveyed farms throughout all 11 geographic regions of the survey. The highest prevalence occurred in the Sydney basin, New South Wales and Victoria east regions. Antibody titres were also highest in the regions where serologically positive flocks were most prevalent. The 259 virus isolates revealed nine different RNA sequences. Of the nine virus groups isolated, the most common group W was identical in sequence to the V4 vaccine strain. Five of the other groups had novel RNA sequences in the region of the F protein cleavage site. CONCLUSIONS: Antibodies to Newcastle disease virus are highly prevalent in the Australian chicken flock but all identified strains were avirulent in nature.  相似文献   

2003年度冬季东海暖流状态分析     

沈建华周甦芳  董玉来崔雪森 《上海水产大学学报》2005,14(1):51-54

由黑潮派生的各种暖流在冬季对东海而言是重要的热能来源,它们的态势会极大地影响东海的温度分布,从而影响到生态系统的变化和发展。通过对2003年度冬东海暖流主干温度、暖舌前锋位置进行空间分析,并与历史状况比较显示今冬的黑潮、台湾暖流和对马暖流都接近历史最强水平,而黄海暖流也比多年平均略强一些。同时期沿岸水体的表面温度与历史的比较结果显示出与多年平均差不多的状况,且在整个冬季表现出明显地随沿岸气候变化的波动状态。所以,2003年度冬暖流的强势对暖流附近海域有一定的影响但并未波及沿岸海域。而对黑潮与其他暖流、沿岸水体以及中西太平洋热带表面水温的相关分析表明,黑潮对对马暖流、台湾暖流有很强的影响作用,但对黄海暖流、沿岸水体的影响不明显,此外,黑潮的水温变化则与中西太平洋热带海域水温的变化有关。  相似文献   

Ryegrass staggers     

IJ Cunningham  WJ Hartley 《New Zealand veterinary journal》2013,61(2)

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Descriptive overview of the 2011 epidemic of arboviral disease in horses in Australia     

SE Roche  R Wicks  MG Garner  IJ East  R Paskin  BJ Moloney  M Carr  P Kirkland 《Australian veterinary journal》2013,91(1-2):5-13

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Ancient mantle in a modern arc: osmium isotopes in izu-bonin-mariana forearc peridotites   总被引：2，自引：0，他引：2  

IJ Parkinson  CJ Hawkesworth  AS Cohen 《Science (New York, N.Y.)》1998,281(5385):2011-2013

Mantle peridotites drilled from the Izu-Bonin-Mariana forearc have unradiogenic 187Os/188Os ratios (0.1193 to 0.1273), which give Proterozoic model ages of 820 to 1230 million years ago. If these peridotites are residues from magmatism during the initiation of subduction 40 to 48 million years ago, then the mantle that melted was much more depleted in incompatible elements than the source of mid-ocean ridge basalts (MORB). This result indicates that osmium isotopes record information about ancient melting events in the convecting upper mantle not recorded by incompatible lithophile isotope tracers. Subduction zones may be a graveyard for ancient depleted mantle material, and portions of the convecting upper mantle may be less radiogenic in osmium isotopes than previously recognized.  相似文献   

Gonadotrophin–releasing hormone administered in continuous low dose can induce ovulation and normal corpora lutea in acyclic post–partum ewes and seasonally anoestrous ewes     

PJ WRIGHT  AH WILLIAMS  IJ CLARKE 《Australian veterinary journal》1994,71(4):123-125

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