Growth rates and patterns of organs and tissues in the bovine fetus.

Ninety-two purebred Jersey fetuses from clinically normal dams derived from a variety of sources but unexposed to experimental infection, were killed between 80 and 260 days after conception and dissected to provide basic parameters of a normal population. Organs and tissues were weighed and measured and the equations for the regression of the values on fetal age evaluated. Growth followed a sigmoid curve with rapid changes in growth rate between 140 and 170 days' gestation. While a few variables increased their growth rate over the late fetal period, the majority maintained a low even rate of growth. Thyroid and cerebellum weights showed a marked reduction in growth rate at this time. Long bone length and crown-anus length were the most predictable parameters for a given gestational age.

Estimation of the developmental age of the bovine fetus and newborn calf.

Jersey cows from several herds provided 97 fetuses and 24 calves at fixed gestational intervals between 80 and 290 days after conception. The fetuses and calves were killed, weighed and measured and, after dissection, the sizes and weights of a range of skeletal and soft tissues were recorded. Six morphological measurements emerged as most suitable for the determination of developmental age in the normal fetus. By plotting their mean values and 95 per cent tolerance limits, the rates of growth and the variability of each measurement were defined. Long bone length was the most useful single measurement for predicting the developmental age of the fetus. Brain weight, bodyweight, crown-anus length and long bone length showed curvilinear growth patterns; age prediction equations derived from these measurements are complicated to use and additional simplified formulae have been derived. The number of appendicular ossification centres also had predictive value, but it could not be used to determine fetal developmental age between 100 and 160 days gestation.

An international collaborative study of an anti-infectious bursal disease virus reference serum.

Fourteen laboratories participated in a collaborative study of a freeze-dried preparation of anti-infectious bursal disease virus serum to assess the suitability of the serum as a standard for use in the infectious bursal disease virus neutralization test. Ten laboratories carried out micro-virus neutralization tests and six carried out plaque reduction tests, two laboratories carrying out both tests. When titres were expressed as a proportion of that obtained for a reference preparation there was a marked reduction in variation between results from different laboratories. The use of a reference preparation was therefore of value when comparing results from different laboratories. It is proposed that the reference preparation used in this study be used as a standard to facilitate the comparison of results from different laboratories. The proposed standard contains by definition 10,000 UK units.

Ovine coccidiosis: studies on the pathogenicity of Eimeria ovinoidalis and E. crandallis in conventionally-reared lambs, including possible effects of passive immunity.

No pathogenic effect was detected in lambs when 10(4) oocyts of each species were inoculated before 72 h of age. At 4 weeks of age the combined inoculum caused diarrhoea and weight loss, the severity being roughly proportional to the size of the inoculum. Even 1000 oocysts of each species caused diarrhoea; the pathogenic effect was attributable mainly to E. ovinoidalis. Hyperimmunization of ewes during pregnancy (by repeated inoculation of massive doses of oocysts) reduced the effects of oocyst inoculation in their progeny. Levamisole administration during pregnancy increased the birthweight of lambs.

Spastic syndrome in a Holstein bull: a histologic study.

A 4-year-old Canadian holstein bull developed the spastic syndrome, an episodic but progressive disorder causing pelvic limb muscular spasms. A post-mortem study, including morphometry of skeletal muscles and teased peripheral nerve fibers of the pelvic limb, revealed mild type II skeletal muscle fiber atrophy and minimal, focal segmental demyelination with remyelination, and axonal degeneration in peripheral nerves. Such alterations are probably incidental or age-associated. Idiopathic muscular cramps is the most probable explanation of the clinical disease and is consistent with the absence of significant morphologic pathologic lesions.

Canine parvovirus serology: a collaborative assay.

Fifteen laboratories were supplied with coded samples of canine sera for testing for the presence of antibodies against canine parvoviruses. One of these sera had been designated as a potential British standard canine parvovirus antiserum. Most of these laboratories were either providing a canine parvovirus serology service, or represented pharmaceutical companies which manufacture canine parvovirus vaccines for the United Kingdom market. No attempt was made to influence the test methods used. Thirteen of the laboratories used a haemagglutination inhibition test, three an enzyme-linked immunosorbent assay (ELISA), and two performed serum neutralisation tests. Three laboratories used two different techniques. Adequate analysis was possible only with the results of the haemagglutination inhibition tests. The variability of the results between laboratories could be partly controlled by the use of the standard serum. Much of the residual variability was associated with particular laboratories. The results from the vaccine manufacturers tended to be less variable than those from the diagnostic laboratories.

Border disease of sheep: spinal cord morphometry.

Semi-automated planimetry was used to determine cross-sectional areas of spinal grey and white matter by direct microscopy of paraffin sections of spinal cord from Border disease (BD) and normal lambs at segments C4, C8, T6 and L4. Spinal cord cross-sectional area was significantly reduced in cases of BD produced by either intramuscular or intranasal inoculation of ewes in the first half of pregnancy with Weybridge strains of BD virus. The reduction was apparent at all 4 levels and in both grey and white matter, though the white matter was the more severely affected. Spinal cord areas tended to be smaller in the progeny of ewes exposed earlier in gestation or to larger doses of virus, but these differences were not statistically significant.

Establishment of a statistical base for use of ELISA in diagnostic serology for infectious bovine rhinotracheitis.

The critical statistical parameters of an enzyme-linked immunosorbent assay were determined to enable quantitation of antibody responses in cattle affected with infectious bovine rhinotracheitis. A system of controlling well-to-well variations in optical density reading across a microtitre plate was evolved and dose--response assays were carried out to determine the dilution of serum which gave the greatest discrimination between acute and convalescent sera from an infected animal. Use of a standard serum was studied in further assays. An increase in optical density value of 0.15 was set as a diagnostic criterion for a significantly rising antibody response. This compared well with the conventional criterion of a fourfold rise in virus neutralizing antibody titre.

Detection of antibodies against infectious bursal disease virus: a comparison of three serological methods.

Four different oil emulsion infectious bursal disease virus (IBDV) vaccines were inoculated into four-week-old specific pathogen-free chickens. At weekly intervals for five weeks, sera were obtained from the vaccinated birds and from uninoculated control birds and examined for antibodies against IBDV by enzyme-linked immunosorbent assay (ELISA), the quantitative agar gel precipitin (QAGP) test and the virus neutralisation (VN) test. There was a highly significant correlation between the mean responses to all tests; the highest correlation (0.818) was between VN and QAGP and the lowest (0.573) between QAGP and ELISA. Generally the ELISA detected positive sera earlier than the VN test which in turn was more sensitive than the QAGP test. The ELISA and QAGP test were less variable, more reproducible and easier to perform than the VN test.

Bovine virus diarrhoea-mucosal disease virus-induced fetopathy in cattle: Efficacy of prophylactic maternal pre-exposure.

Maternal immunity was produced in Jersey heifers by exposing them to bovine virus diarrhoea-mucosal disease virus before conception. In the following pregnancy this immunity protected the fetuses from transplacental infection arising from challenge of the dams at 100 days gestation with homologous virus. Unprotected Jersey heifers showed a high incidence of death and fetal intrauterine growth retardation associated with transplacental viral infection. Functional normality of the locomotor system was assessed retrospectively from ciné films of each calf after birth, and scored for each of an overlapping series of clinical signs. The progeny of non-immune dams scored significantly lower than calves from the vaccinated heifers.

Atrophic rhinitis: snout morphometry for quantitative assessment of conchal atrophy.

Morphometric methods, either point counting or semiautomated planimetry, can be applied to photographic or impression prints of sections of the pig snout to measure the extent of conchal atrophy on a continuous scale as a morphometric index. Though relatively time consuming, the technique yields highly repeatable parametric data which do not depend heavily on expert, subjective judgment. It is therefore particularly suitable for quantitative analysis of the effects of experimental treatments or changes in management.

The use of reference preparations in virus content testing of vaccines.

A series of virus content tests on Newcastle disease, avian infectious bronchitis and Marek's disease vaccines was carried out over a period of several years on commercial products together with a standard preparation of each virus. Analysis of the results of Marek's disease vaccine titrations revealed a good correlation between plaque count and the ratio obtained for the standard vaccine tested in parallel. Expression in relation to a reference preparation is therefore of value to vaccine manufacturers and quality control authorities as a method of reducing variation among assays carried out on different occasions or by different laboratories. For infectious bronchitis vaccines, expression in relation to a standard was of less value and the method was of little help for evaluating Newcastle disease vaccines. However, in each case, the standard preparation was of value in judging the acceptability of assays.

Incidence of hypocupraemia in cattle in the east Midlands.

Serum copper values were determined on composite samples from cattle herds in the Midland counties of Derbyshire, Leicestershire and Nottinghamshire. Sampling took place over a period of 17 months and the results indicate that hypocupraemia existed in many herds. The lowest values were found in heifer group samples and the lowest of these was found in Derbyshire. The geographical and management factors which may affect the copper status of herds in this area are discussed.

Congenital tremor type AI: light and electron microscopical observations on the spinal cords of affected piglets.

The histology and ultrastructure of the spinal white matter from the dorsolateral funiculus of the third cervical segment was studied in normal control pigs and pigs whose dams were inoculated with the Weybridge congenital tremor strain of swine fever virus in early pregnancy. Only inoculated sows produced abnormal piglets. These showed congenital tremors and ataxia. The severity of clinical signs was related to the degree of spinal myelin deficiency. Morphologically this was quantified by determination of the thickness of myelin investing axons classed according to their diameter. In clinically affected pigs fewer axons were myelinated than normal. Though the myelin sheath thickness increased with increasing axon diameter in all pigs whether clinically normal or not, the increase was less in moderately affected and much less in severely affected pigs. The deficiency of spinal myelin was probably due to delayed or sub-normal myelination accompanied by paranodal myelin abnormalities, myelin degeneration and remyelination.