Annales de recherches veterinaires. Annals of veterinary research最新文献

Forty-eight heifers were given selenium and/or vitamin E or no supplementation from age of weaning (8 months) for 6 months prior to breeding. Blood plasma levels were monitored and some reproductive traits were assessed. The overall pregnancy rate (33%) in the control group was significantly (P less than 0.05) lower than in the vitamin E-supplemented groups (58-83%). Age of first heat, breeding and calving were unaffected by vitamin E and/or selenium supplementation.

Two rabies virus strains collected from naturally infected foxes in France in 1976 and 1986 were inoculated in 2 groups each consisting of 10 foxes (approximately 50 lethal doses50 mouse intracerebral per fox). Another 20 healthy foxes were kept in the same cages as the inoculated animals in order to study the transmission of both strains. All the inoculated foxes became rabid and transmitted rabies to their cage companion. The intervals between death of the inoculated foxes and death of the cage companion were significantly more variable (P less than 0.001) with the earlier strain, from 1 to 33 days compared to the range obtained with the later strain, 10-14 days. However, the mean intervals did not differ. Epidemiological consequences of such a decrease in variability, if confirmed in the field could decrease the epidemiological extent of rabies. Viremia was demonstrated in 2 foxes inoculated with the later strain but we cannot assume this to be a characteristic of this strain compared with the earlier strain. Rabies virus (both strains) was isolated from the saliva of foxes 29 days or less before the onset of clinical symptoms. This last result raises the question of the time limit as regards security before onset of clinical symptoms in animals involved in human contamination.

The virus isolated from young dromedaries during a poxvirus infection, was cultivated on Vero cells. The infection of egg chorio-allantoic membrane caused pustulous lesions (pocks). When inoculated in newborn mice, adult mice or guinea pigs the virus had no pathogenic effect. The virus presented all the characteristics of a poxvirus when observed under the electronic microscope.

Xiphophorine fish from wild populations are insusceptible of developing neoplasia. In contrast, certain backcrosses of Xiphophorus maculatus (platyfish) with Xiphophorus helleri (swordtail) as the recurrent parent produce offspring that develop neoplasia in a Mendelian fashion. We concentrated our research on melanoma. To construct a fish strain which is highly susceptible to mutagenic carcinogens, a particular regulatory gene, ie an oncosuppressor gene (Bs), was introduced into the fish developing the Mendelian inherited melanoma by introgression. Bs prevents the progeny from developing melanoma. However, Bs can be impaired by carcinogen-induced somatic mutation which gives rise to the development of clonal melanoma. Activity of the oncogene x-src (measured on pp60x-src kinase activity) and inositol lipid turnover is elevated in the tumor but, in contrast to the animals bearing the inherited melanoma, not in the brain. Tumor promoters do not induce melanoma in this strain. Similarly, in order to breed a fish strain which is highly susceptible to tumor promoters we introduced a regulatory gene, for instance an oncostatic gene (g) coding for a pretransformational arrest of pigment cell differentiation in the stem cell stage of the fish that develop the Mendelian inherited melanoma. The new strain is incapable of developing melanoma. Its x-src kinase activity and inositol lipid turnover is elevated in the brain, indicating that the biochemical processes which were found to be correlated with the hereditary melanoma formation, operate without the occurrence of melanoma. Following treatment of these animals with tumor promoters, melanoma develops within a very short latent period. Our tester strain can discriminate between tumor-initiating and tumor-promoting activities of agents of unknown carcinogenic potential.

In the United States, the Food and Drug Administration has developed a scientifically sound and rational approach to assure human safety from both naturally occurring and synthetically-derived hormones used in animal production. On this basis, estradiol, progesterone, androsterone, zeranol and trenbolone have been registered. For trenbolone a maximal residue limit of 50 ppb for meat has been accepted.

Besides the 3 aspects of drug safety, ie stability, efficacy and harmlessness, a fourth hurdle for veterinary drug licensing is discussed: socio-economic criteria. These criteria have not yet been established and the scientific aspects are difficult to define. After discussion of the advantages and disadvantages of the fourth hurdle, the conclusion is that there is no need to introduce a fourth criterion into the admission procedure for veterinary drugs, feed additives or any other chemicals which increase animal health or promote their growth.

Bacterial enterotoxins, produced by some pathogenic bacteria, induce diarrhoea during human or animal digestive infections; most of them act via membrane receptors and are specifically recognized on the enterocyte brush border. These receptors differ in number (which probably determines the degree of enterotoxin toxicity, nature, structure, and specificity. The receptors, ie glycolipids (GM1) or glycoproteins, are well represented on the surface of the enterocyte, and/or in various vertebrate cell types. The enterotoxins bind to the receptor glucoside chains, in which sequences have sometimes been determined. In most cases irreversible binding occurs due to enterotoxin internalization.

Fauna-free wethers were fed bi-hourly a corn silage diet containing casein or soybean meal as a protein supplement. The wethers were inoculated via rumen cannula with a mixed population of ruminal ciliate protozoa. Ruminal fluid was sampled daily for 4 d before and for 13 d (and on d 28) after inoculation. Protozoal populations reached peak numbers on d 8 and decreased to new levels after d 9 for wethers on both supplements. Protozoa decreased (P less than 0.01) the concentrations of total volatile fatty acids, increased (P less than 0.01) the pH and decreased (P less than 0.01) he concentrations of total and non-ammonia nitrogen in ruminal fluid. The concentrations of ammonia nitrogen increased with increasing numbers of protozoa for wethers on both supplements, but the concentrations decreased after d 7 to approximately pre-inoculation levels for the casein-supplemented diet. The increasing numbers of protozoa were associated with the increased concentrations of total and free alpha-amino nitrogen (P less than 0.01) and sulfide (P less than 0.05) and with the decreased concentrations of soluble Cu (P less than 0.05) in the ruminal fluid in soybean meal-supplemented wethers but not in those receiving casein. It was concluded that dietary proteins with differing physical characteristics are metabolized to a different extent by ruminal ciliate protozoa, which in turn can affect the metabolism of other dietary nutrients such as nitrogen and sulfur and contribute to copper-sulfur interaction.

Immunological parameters of porcine peripheral blood mononuclear cells after in vivo injections of recombinant porcine interferon gamma (rPoIFN gamma) were studied in pigs immunosuppressed by dexamethasone (6 mg/kg body weight in a single injection). A 2-d period of rPoIFN gamma injected alone and intramuscularly at a dose of 1 microgram/kg body weight increased interleukin 1 (IL1) production (P less than 0.05). Recombinant porcine IFN gamma also reversed the immunosuppressive effects of dexamethasone on: i), lymphocyte responsiveness to mitogens: PHA (P less than 0.03), ConA (P less than 0.053); ii), IL1 production; and iii), IL2 production (P less than 0.05). However, rPoIFN gamma had no effect on neutrophilia induced by dexamethasone. These data show that rPoIFN gamma modulates leukocyte functions of pigs in vivo.

In the dairy cow, a statistical association between milk fever (MF) and placental retention (PR) has been observed in epidemiological studies. In order to prevent both diseases, an understanding of their common aetiological mechanism is necessary. In this paper, a new causal hypothesis concerning the nutrition-induced association between PR and MF has been put forward. This hypothesis integrates the aetiological concepts arising from the studies carried out by the authors of this paper, and those reviewed from the literature. The aetiological pathway leading to associated MF and PR in the dairy cow appears to include 3 main interrelated mechanisms: 1), decreased synthesis of cyclooxygenase products (mainly PgF2 alpha) via precalving linolenic acid-rich diets; 2), lack of calcium availability at calving via calcium-rich diets before calving; 3), intensive lipomobilization around calving due to a lack of energy supply. The risk for both MF and PR appears to be maximum with old cows fed diets rich in green fodder (fresh or ensiled) and in calcium, and poor in cereals in the prepartum period.