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Intestinal colonization and shedding of pathogenic bacteria in animal feces is an important factor in both human food safety and animal health. The effect of broiler feed additives flavophospholipol (FPL; Flavomycin, bambermycins) and salinomycin sodium (SAL; Sacox) given singly on the excretion of Salmonella enteritidis, Campylobacter jejuni, and Clostridium perfringens was studied following controlled infection. The incidence of shedding (number of birds with positive fecal cultures) and the degree of shedding (cfu per gram of feces in positive birds) were measured to determine the influence of these two common feed additive antibiotics on shedding rates of potential pathogens. A total of 216 Ross broiler chickens, housed in battery cages, were fed either an unmedicated feed (controls), feed containing FPL, or feed containing SAL. Feed treatment groups were subdivided into three bacterial challenge groups of 24 chicks, each receiving only one of the pathogens. Bacterial challenge was administered orally on Days 11 and 12 for Salmonella and Campylobacter and on Days 2 and 3 for Clostridium. Fecal samples were collected weekly up to 6 wk of age and cultured for presence of the target organism. The shedding rate was determined by decimal dilutions of the fecal samples. Feeding FPL resulted in a reduced (P < or = 0.05) degree and incidence of Salmonella and Clostridium shedding at 6 wk. Feeding SAL reduced (P < or = 0.05) the incidence of Salmonella shedding at 6 wk. Neither feed additive affected the incidence nor the degree of Campylobacter shedding. The results of this study indicate that these feed additives may reduce the incidence of these potential human and animal pathogens in preslaughter broilers.

We have developed an assay for the detection of pathogenic Leptospira that is based on the polymerase chain reaction. With the combination of agarose gel electrophoresis and blotting, pathogenic Leptospira can be discriminated specifically from nonpathogenic Leptospira and other bacterial species. This method, based on the amplification of 16S ribosomal RNA sequences, is able to detect 10 leptospiral cells/mL in cattle urine samples and 100 leptospiral cells/mL in pig urine samples. Using this assay leptospires were detected in urine samples from cattle that were experimentally infected with Leptospira interrogans serovar hardjo type hardjobovis.

The polymerase chain reaction (PCR) is a technique that enables us to prepare in a test tube billions of copies of a specific piece of DNA. The principles and practical aspects of the PCR are exposed. Within veterinary medicine the most important applications are expected to be i) the diagnostics of infectious diseases and ii) the detection of genetic disorders or desired genetic traits. The PCR can be carried out on a multitude of samples ranging from mummies to paraffin-embedded tissue specimens. However, inhibitors present in e.g. serum, urine and faeces have to be removed.

In 6 days' chick embryos, an electronmicroscopical study was made of the fusion of the endocardial ridges of the truncus arteriosus. It could be demonstrated that in this fusion process not only the endothelial cells are involved, but also cells of the condensed mesenchyme of the parietal ridge. The endothelial cells form protrusions which interdigitate and show endocytosis whereas the cells of the condensed mesenchyme produce long, blunt pseudopodia containing filaments and microtubules.

A comparative study was made of the relative position of the outflow tracts of chicken and rat hearts with respect to the ventricles during septation. For this purpose the position of the left and right ventricular outlet including the aortic and pulmonary valve primordia and the left and right ventricle were established with respect to the midsagittal plane of the embryo, using reconstructions of serial sections of chicken (stage 28-30) and rat (stage 28-30) embryos. In the chicken embryo no rotation of the outflow tract occurs, i.e. the position of the aortic and pulmonary valve primordia with respect to the left and right ventricle remains the same. In the rat embryo a clockwise rotation of the aortic and pulmonary valve primordia with respect to the ventricles does occur. This is in fact a detorsion. The left and right ventricle and the left ventricular outlet do not show change in position with regard to the midsagittal plane. The left ventricular outlet always straddles the interventricular septum, both lying in the midsagittal plane. These interspecies differences in the degree of detorsion of the outflow channels before septation may explain the differences in the extent of the region of contact between the endocardial outflow tract ridges.