Mycotoxicoses of domestic animals and their diagnosis

Mycotoxins have been named "agents in search of a disease," and the considerable progress in analytical methodology over the last 10 years has not changed this very much. The following are factors that contribute to the difficulty of making a diagnosis: (1) nonspecificity of lesions; (2) masking of mycotoxic effects by secondary effects, e.g., through immunosuppression; (3) late appearance of a lesion, e.g., bone marrow damage or neoplasia; (4) interaction of several mycotoxins or presence of other toxicants or deficiency states; (5) species variation in the response to the mycotoxin(s); (6) difficulty of linking a late appearing effect with a demonstrable cause; (7) low doses of mycotoxins may cause stimulating effects; and (8) not being aware of the potential of a mycotoxin as a causative factor in disease. The mycotoxins of major importance in Canada are trichothecenes, ochratoxin, zearalenone, and ergot. It is concluded that the significance of mycotoxins for animals in Canada is likely generally underestimated.     

动物的孤雌生殖

孤雌生殖（parthenogenesis）也叫做“单性生殖或处女生殖”。孤雌生殖的定义是：“雌性个体产生的卵,无需受精．可发育成新雌性个体。”植物也可能有类似的情形,但植物受精作用的细节多少有些不同,所以这个定义只适用于动物。     

Evo-devo of non-bilaterian animals

The non-bilaterian animals comprise organisms in the phyla Porifera, Cnidaria, Ctenophora and Placozoa. These early-diverging phyla are pivotal to understanding the evolution of bilaterian animals. After the exponential increase in research in evolutionary development (evo-devo) in the last two decades, these organisms are again in the spotlight of evolutionary biology. In this work, I briefly review some aspects of the developmental biology of nonbilaterians that contribute to understanding the evolution of development and of the metazoans. The evolution of the developmental genetic toolkit, embryonic polarization, the origin of gastrulation and mesodermal cells, and the origin of neural cells are discussed. The possibility that germline and stem cell lineages have the same origin is also examined. Although a considerable number of non-bilaterian species are already being investigated, the use of species belonging to different branches of non-bilaterian lineages and functional experimentation with gene manipulation in the majority of the non-bilaterian lineages will be necessary for further progress in this field.     

动物的求偶喂食行为

动物的求偶喂食行为是雄性动物在求偶时向求偶对象奉献食物礼品的现象,这种行为在昆虫、蜘蛛和鸟类中最为常见。介绍了求偶喂食行为的概念,列举了一些实例,并讨论了这种行为的生物学功能和进化过程。     

Lightning safety of animals

This paper addresses a concurrent multidisciplinary problem: animal safety against lightning hazards. In regions where lightning is prevalent, either seasonally or throughout the year, a considerable number of wild, captive and tame animals are injured due to lightning generated effects. The paper discusses all possible injury mechanisms, focusing mainly on animals with commercial value. A large number of cases from several countries have been analyzed. Economically and practically viable engineering solutions are proposed to address the issues related to the lightning threats discussed.     

Anthrax in animals

Anthrax is the archetype zoonosis; no other infectious disease affects such a wide range of species, including humans, although most susceptible are herbivorous mammals. Although the disease appears to have been recognized for centuries, it has yet to be established scientifically how animals contract it. While primarily a disease of warmer regions, it has long been spread to cooler zones through the trade of infected animals or contaminated animal products. Today it is still endemic in many countries of Africa and Asia and non-endemic countries must remain alert to the possibility of imports from such endemic areas resulting in outbreaks in their own livestock. The epidemiology of anthrax is becoming understood better with new systems coming on stream for distinguishing different genotypes and this is covered in detail. Clinical signs and pathology in animals are described.     

Clostridium difficile in young farm animals and slaughter animals in Belgium

Faecal carriage of Clostridium difficile in healthy animals has been reported recently, especially in piglets and calves. However there is limited data about carriage in animals just prior to slaughter in Europe. The main objective of this study was to determine the presence of C. difficile in pigs and cattle at the slaughterhouse. C. difficile was isolated in 6.9% of the cattle at the slaughterhouse. None of the pig slaughter samples were positive for C. difficile after an enrichment time of 72 h. For complementary data, a short study was conducted in piglets and calves at farms. C. difficile was more prevalent in piglets (78.3%) than in calves (22.2%) on the farms. Regarding the piglet samples, 27.8% of the positive samples were detected without enrichment of stools. The PCR ribotype 078 was predominant in farm animals. Samples isolated from slaughter cattle presented the widest range in PCR-ribotype variety, and the most prevalent PCR ribotype was 118a UCL. The results of this study confirm that C. difficile is present in slaughter animals in Belgium with a large percentage of toxigenic strains also commonly found in humans.     

Spatial distribution of dispersing animals

Summary A mathematical model for the dispersal of an animal population is presented for a system in which animals are initially released in the central region of a uniform field and migrate randomly, exerting mutually repulsive influences (population pressure) until they eventually become sedentary. The effect of the population pressure, which acts to enhance the dispersal of animals as their density becomes high, is modeled in terms of a nonlinear-diffusion equation. From this model, the density distribution of animals is obtained as a function of time and the initial number of released animals. The analysis of this function shows that the population ultimately reaches a nonzero stationary distribution which is confined to a finite region if both the sedentary effect and the population pressure are present. Our results are in good agreement with the experimental data on ant lions reported by Morisita, and we can also interpret some general features known for the spatial distribution of dispersing insects.