Comparison of dot blot hybridization, polymerase chain reaction, and virus isolation for detection of bovine herpesvirus-1 (BHV-1) in artificially infected bovine semen.

Bovine semen samples spiked with bovine herpesvirus 1 (BHV-1) were used to compare dot blot hybridization, polymerase chain reaction (PCR), and virus isolation for detection of BHV-1 in bovine semen. The PCR amplification used primers targeting the BHV-1 thymidine kinase gene and a nucleic acid releasing cocktail (GeneReleaser); the PCR product was used as the DNA probe in dot blot hybridization; virus isolation was done in primary bovine fetal testis (BFT) cell cultures. Semen diluted 1:20 in tissue culture medium had the least cytotoxicity and inhibition of viral cytopathic effects in BFT cells, allowing detection of 1 TCID50/100 microL of BHV-1 suspension by virus isolation. The presence of foreign DNA such as bovine sperm DNA or salmon sperm DNA increased the sensitivity of dot blot hybridization in detecting BHV-1, allowing detection of 20,000 TCID50/100 microL of neat semen. The inhibition of PCR amplification of BHV-1 DNA in bovine semen was eliminated by diluting the samples 1:20 in tissue culture medium. The best PCR amplification was obtained when semen was diluted 1:20 and when a reaction buffer of pH 9.0, with 1.0 mM MgCl2 was used. Under these conditions, the PCR followed by ethidium bromide staining of agarose gels could detect 1 TCID20/100 microL of sample, whereas PCR followed by Southern blot hybridization could detect 0.01 TCID50/100 microL of sample.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of inoculum density of Macrophomina phaseolina on seedling susceptibility of six conifer species

The severity of charcoal root disease of conifer seedlings (Abies concolor, A. magnified, Pinus jeffreyi, P. lambertiana, and Pseudotsuga menziesii) was a power function of the sclerotial density of the fungus (Macrophomina phaseolina) in nursery soil.     

A rapid monoclonal immunofluorescence assay for Chlamydia psittaci in fecal smears from psittacine birds

One hundred two fecal specimens from psittacine birds submitted to Veterinary Laboratory Services of the California Department of Food and Agriculture at Petaluma were screened for Chlamydia psittaci by a direct immunofluorescence assay using a fluorescein-labeled monoclonal antibody conjugate specific for Chlamydia sp. Results were compared with those obtained by isolation of chlamydia in cultures of McCoy mouse cells. The relative specificity of the direct fluorescent antibody test on fecal smears was 98.9% and the relative sensitivity was 62.5%. The results of this study suggested that the direct fluorescent antibody test was highly specific, and it proved to be a useful same-day antemortem diagnostic test for birds with symptomatic chlamydial infection. The use of centrifugation in the cell culture assay was found to significantly enhance the level of chlamydial infection in cell culture.     

Effect of age on absorption and immune responses to weaning or introduction of novel dietary antigens in pigs

Pigs weaned at three weeks old absorb food protein antigens from the intestine. The amount of antigen absorbed declines over the next three weeks, and this decline is associated with an increasing level of serum antibody to the fed proteins. There was no difference in the rate of immune elimination of intravenously injected antigen in fed and unfed controls. The reduction of serum antigen is thus likely to reflect reduced absorption, possibly mediated by locally produced antibody. Pigs weaned at 10 weeks old also absorbed antigens and produced an antibody response when introduced to soya; and after three weeks of feeding soya the absorption of antigen was substantially reduced. This latter exclusion was specific for soya as a second novel protein (ovalbumin) was absorbed when introduced to the diet at this time. At six months, pigs no longer absorbed soya proteins when they were introduced to the diet. Furthermore, pigs of this age had serum 'antibody' to soya and other proteins such as keyhole limpet haemocyanin to which they had never been exposed.     

Comparative virulence of NAD-dependent and NAD-independent Actinobacillus pleuropneumoniae strains.

The virulence of a NAD-independent Actinobacillus pleuropneumoniae serotype 2 strain and NAD-dependent serotype 2, 3 and 9 strains was compared under experimental conditions. Hysterectomy-derived piglets were inoculated endobronchially with 50-500 cfu of these strains. All 23 piglets inoculated with the NAD-dependent strains developed acute disease within 12 hours post inoculation. Twenty-two of these piglets died within 24 hours after the first clinical signs. Three of nine piglets inoculated with the NAD-independent strain did not develop clinical disease. In the other six piglets, disease signs were similar as in the piglets inoculated with the NAD-dependent strains. No differences in clinical disease were observed between colostrum deprived piglets and piglets that obtained colostrum from a SPF sow.     

Destruction of Trichinella spiralis spiralis during the preparation of the "dry cured" pork products proscuitto, proscuittini and Genoa salami

Genoa salami, proscuittini and proscuitto were prepared from pork carcasses that were heavily infected experimentally with Trichinella spiralis spiralis. Genoa salami was prepared with salt concentrations of 2.0%, 2.75% and 3.3%. Proscuitto was prepared by two procedures approved by Agriculture Canada. At various times postpreparation, samples of the various cured products were taken and examined by pepsin digestion and rat bioassay for the presence of viable trichinae. Water activity and pH of the cured meat were also determined. Curing of the various products was shown to destroy the Trichinella larvae. Pepsin digestion revealed that larvae progressively became loosely coiled, uncoiled and more subject to digestion (ghost larvae) during the curing process. Rat bioassay revealed the presence of viable trichinae in the proscuitto prepared using a sodium chloride salt mixture at day 34 but not at day 48 postpreparation. All other bioassays carried out on Genoa salami between 13 and 42 days postpreparation, on proscuittini between days 27 and 69 and on proscuitto between days 34 and 69 were negative for viable trichinae. Under the conditions of this study, preparing Genoa salami with salt concentrations as low as 2% did not appear to affect the destruction of Trichinella larvae.     

In vitro evaluation of protein degradability in the rumen and digestibility of undegraded protein

A three-phase laboratory procedure suitable for predicting protein degradability in the rumen and digestibility of undegraded protein is reported. In the first phase the feed was incubated with starch and buffered rumen fluid. In the incubation mixture the viability of protease-active bacteria was checked by anaerobic culturing, whereas changes in protease activity were monitored by azocasein degradation. In the second and third phase rumen undegradable protein (UDP) was digested with pepsin and pancreatin, respectively. The measurements showed that 63.2, 5.2 and 4.7% of the crude protein of green lucerne was decomposed by rumen fluid, pepsin and pancreatin, respectively. Degradability of the crude protein of extracted sunflower meal was 68.3, 17.7 and 5.5% in the three phases, respectively. Repeated determination yielded crude protein degradabilities of 66.7, 27.1 and 5.1% for the three phases, respectively.     

Influence of age on the febrile response to E. coli and S. typhimurium endotoxins in growing pullets.

1. The effect of bacterial endotoxin injection was studied in growing pullets of different ages. Commercial chicks were divided into 5 groups according to age. Bacterial endotoxins (E. coli and S. typhimurium) were injected intravenously and rectal temperature was measured over a period of 300 min. 2. The results showed no significant effect of age on the febrile response induced by bacterial endotoxins, but a slight tendency towards a reduced fever peak was observed with increasing age. The response latency also increased with age.