摘要:

In dairy cows, overfeeding during the dry period leads to overcondition at calving and to depression of appetite after calving. As a consequence, at calving overconditioned high‐producing dairy cows inevitably go into a more severe negative energy balance (NEB) postpartum than cows that have a normal appetite. During the period of NEB, the energy requirements of the cow are satisfied by lipolysis and proteolysis. Lipolysis results in an increased concentration of non esterified fatty acids (NEFA) in the blood. In the liver, these NEFA are predominantly esterified to triacylglycerols (TAG) that are secreted in very low density lipoproteins (VLDL). In early lactation in cows with a severe NEB, the capacity of the liver to maintain the export of the TAG in the form of VLDL in balance with the hepatic TAG production is not always adequate. As a result, the excess amount of TAG accumulates in the liver, leading to fatty infiltration of the liver (hepatic lipidosis or fatty liver). The NEB and/or fatty liver postpartum are frequently associated with postparturient problems. In general, a severe NEB induces changes in biochemical, endocrinological, and metabolic pathways that are responsible for production, maintenance of health, and reproduction of the postparturient dairy cow. These changes include a decrease in blood glucose and insulin concentrations, and an increase in blood NEFA concentrations. High NEFA concentrations caused by intensive lipolysis are accompanied by impairment of the immune system, making the cows more vulnerable to infections. Metabolic diseases such as ketosis, milk fever, and displaced abomasum are related to overcondition at calving. The changes in biochemical, endocrinological, and metabolic pathways are associated with delay of the first visible signs of oestrus, an increase in the interval from calving to first ovulation, a decrease in conception rate, and a prolonged calving interval. It is possible that the increased blood NEFA concentration directly impairs ovarian function.

ISSN:0165-2176    

DOI:10.1080/01652176.1999.9694997

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The present paper presents an overview of current knowledge of amyloid arthropathy in chickens, and covers the pathogenesis of amyloidosis in general and in birds, field cases reported, and the studies performed to assess the amyloidogenicity of various agents compared to that ofEnterococcus faecalis. An animal model of amyloid arthropathy is presented, as are studies on the pathogenesis of arthropathic and amyloidogenicE. faecalisinfections in brown layers. The review concludes with a description of the pathology of amyloid arthropathy, the biochemical characterization of the chicken joint amyloid protein as being of the AA type, investigation of the serum amyloid A (SAA) gene involved, and local SAA mRNA expression in joint and liver.

ISSN:0165-2176    

DOI:10.1080/01652176.1999.9694998

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A review of the literature of the functional anatomy and neural regulation of the lower urinary tract is presented. The two main functions of the lower urinary tract are the storage and the periodic elimination of urine. The smooth muscle of the bladder exhibits intermittent contractions as the bladder adapts its capacity to increasing volumes and it exhibits sustained contractions associated with relaxation of the external sphincter to effect micturition. During storage, tension receptors in the bladder wall initiate external sphincter contraction (somatic), internal sphincter contraction (sympathetic), detrusor inhibition, and parasympathetic ganglion inhibition (sympathetic). The storage phase can be switched to the micturition phase either voluntarily or involuntarily. Neuroanatomical and electrophysiological studies reveal that medial and lateral cell groups in the dorsolateral pons may be regarded as micturition and storage control centres, respectively.

ISSN:0165-2176    

DOI:10.1080/01652176.1999.9694999

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The epidemic of bovine spongiform encephalopathy (BSE) has been the most expensive disaster ever to have befallen farming in the UK. It is believed to have led to a new form of spongiform encephalopathy in humans and as yet there is no way of knowing how many people will die of this disease. In order to curtail the BSE epidemic major decisions had to be made, often on the basis of inadequate scientific data. These data may have been derived from experiments using small sample numbers. Here we review some examples of where this has happened, sometimes with a beneficial outcome and sometimes with a misleading outcome. The identification of BSE as a new disease depended on precise neuropathological observation of a small number of cases rather than the obvious occurrence of large numbers of sick animals. Similarly, the recognition that BSE may have led to disease in humans was based on the neuropathological and clinical picture of new variant Creutzfeldt‐Jakob disease (CJD) rather than on an increase in the number of cases of CJD in the UK. Early in the BSE epidemic the possibility that disease could be maternally transmitted from cow to calf was raised, mainly because of a belief that such transmission occurs in scrapie disease of sheep. But, we argue, the evidence for maternal transmission of scrapie, collected in the 1960s, was based on small numbers and is inadequate. Subsequent research has shown a very substantial genetic component in scrapie and epidemiological data show no excess risk in the offspring of affected ewes relative to the risk in the offspring of affected rams. An experiment to determine whether maternal transmission occurs in BSE was flawed and was unable to distinguish between maternal transmission and genetic susceptibility to environmental contamination. An assessment of the risk of BSE to humans depends on determining the levels of infectivity in tissues and transmissibility across species. Data on both of these are deficient, so it is not possible to predict how many people in the UK or elsewhere will become affected with new variant CJD in the next fifty years. The assessment of whether BSE could be transmitted to sheep and whether sheep therefore pose a risk to humans is hampered by a serious lack of evidence about the epidemiology of scrapie in the UK and elsewhere. The UK has paid a heavy price for the BSE epidemic but lessons should be learned from the experience. Every country should have a Specified Offals Ban even if it has no cases of BSE because, by the time it has, it will be too late. Furthermore, the occasional case of BSE should not be regarded as insignificant since it may be the harbinger of an epidemic in the making.

ISSN:0165-2176    

DOI:10.1080/01652176.1999.9695000

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In a controlled field study of three years’ duration we evaluated the effect of cobalt supplementation on pathological changes in cobalt/vitamin B12‐deficient Texel twin lambs grazing the same cobalt‐deficient pasture. Semi‐quantitative evaluation of the histopathology of liver and brain was done on 44 sets of twins. Pathological changes were related to blood concentrations of vitamin B12, methylmalonic acid, and homocysteine.

ISSN:0165-2176    

DOI:10.1080/01652176.1999.9695001

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Recently a commercial computer‐controlled image image analysis system (IAS) was introduced to measure automatically the diameters of inhibition zones in the agar diffusion test. However, there is little information on the precision of this method. In the present study clinical isolates ofSalmonellaspp. (N = 104),Escherichia coli(N = 100),Pasteurellaspp. (N = 99),Actinobacillus pleuropneumoniae(N = 85), porcine streptococci (N = 100), andStaphylococcus aureus(N = 95) were tested in the agar diffusion test, using nineteen different antibiotics in tablets. All inhibition zone diameters were first measured by a laboratory technician and then by the IAS. Although the zone diameters of all bacteria‐antibiotic combinations measured by the IAS and those measured by the laboratory technician showed a significant positive correlation, the size of the inhibition zone diameters measured by the technician and the IAS differed significantly in 59% of the combinations. However, these differences were very small and may have no clinical relevance. The IAS was also used to calculate minimum inhibitory concentrations (MIC values) from the zone diameters. In 82% of the bacteria‐antibiotic combinations MIC values calculated by the IAS showed a significant positive correlation with MIC values obtained with the reference agar dilution test. However, in 92% of the bacteria‐antibiotic combinations, the calculated MIC values differed significantly from the reference values. In some cases these differences were so large that they could be of clinical relevance. The IAS was unable to measure the diameter of inhibition zones of porcine streptococci properly, due to poor contrast. We concluded that when tablets are used as antibiotic carriers the IAS accurately measures the diameter of inhibition zones for bacteria species that give good contrast between the agar and bacterial growth. MIC values determined with the IAS were only indicative of those determined with the reference agar dilution test.

ISSN:0165-2176    

DOI:10.1080/01652176.1999.9695002

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In this study, the efficacy of successive intranasal (IN)/intramuscular (IM) vaccination against Aujeszky's disease virus (ADV) was assessed in experimental pigs. The double deletion‐mutant Kaplan gE‐gI‐was used for IN vaccination at 4 weeks of age and the commercially available Bartha strain, suspended in an oil‐in‐water emulsion, was used for the IM booster vaccination at 10 weeks of age. Efficacy was compared with that of the traditional double IM vaccination with the commercially available Bartha strain at 10 and 14 weeks of age by challenging the pigs at the end of the fattening period.

ISSN:0165-2176    

DOI:10.1080/01652176.1999.9695003

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor