Comparison of natural resistance in seven genetic groups of meat-type chicken.

1. Several studies have shown that genetic variation exists in response to various Salmonella strains in mammals and poultry. In the current study immunocompetence traits related to natural resistance to Salmonella were measured in 7 genetic groups of meat-type chickens (in total 296 chickens involved). 2. Variables were measured of both innate (phagocytic activity) and adaptive immune responses that are important after a natural or experimental Salmonella enteritidis infection. Two traditional Old Dutch Breeds (groups 1 and 2), four commercial broiler groups (groups 3 to 6), and one experimental broiler group (group 7) were used. In two periods, birds of each group were killed for examination at ages between 14 and 35 d post hatch. 3. Significant differences between groups were found for most immune variables measured, with significant correlations between several of them. All groups produced an adequate immune response, of either the innate or the adaptive type. 4. In the current study, group 2 showed the highest overall natural resistance, though none of the groups was uniformly superior with respect to all traits measured. 5. In conclusion, for reliable measurements of general immunocompetence or resistance to Salmonella, for example, it is important to measure several aspects of the immune system.

Entry and survival of Salmonella enterica serotype Enteritidis PT4 in chicken macrophage and lymphocyte cell lines.

Various leukocytes are involved in the reaction to counter Salmonella infection in chicken. The various leukocyte types react differently after an infection, since some clear the infection while others may cause dissemination of Salmonella throughout the chicken. Therefore, we investigated in vitro the entry and survival of Salmonella enterica serotype Enteritidis in chicken cell lines of various cell types, including two macrophage cell lines, HD11 and MQ-NCSU (NCSU), two B-cell lines LSCC-1104-X5 (1104) and LSCC-RP9 (RP9), and a T-cell line MDCC-MSB-1 (MSB-1). The macrophages were able to internalize high numbers of S. Enteritidis. In contrast and as expected, cells of the T-cell line MSB-1 and the B-cell line RP9 internalized bacteria at a much lower level. After S. Enteritidis entered the macrophages, the number of intracellular S. Enteritidis decreased over time, so that after 48h no more than 20% of the bacteria, which had entered, survived intracellularly. In contrast to macrophages, the number of S. Enteritidis in cells of the T-cell line MSB-1 and the B-cell line RP9 increased rapidly within 12h post-inoculation. Thereafter the number of intracellular S. Enteritidis decreased only slowly. In conclusion, all three different cell types were able to control and to start clearing S. Enteritidis, although macrophages were far more effective compared to T- and B-cells. However, none of the cell lines were able to clear S. Enteritidis fully within 48h. These results suggest that the three cell types play an important but different role in the dissemination and elimination of S. Enteritidis throughout the animal.

Disease incidence and immunological traits for the selection of healthy pigs. A review.

Disease is a major issue in animal production systems and society demands that the use of medicines and vaccines be reduced. This review describes the breeding approaches that could be used to improve disease resistance and focuses especially on their application to pigs. Disease reduction by genetic means has certain advantages through cumulative and permanent effects, and direct and indirect selection methods are available. Direct selection for disease incidence requires, besides a unique pig identification and disease registration system, challenge routines that are inconvenient in intensive pig production. Indirect selection for the expression of immune capacity may be an alternative but requires detailed knowledge of the different components of the immune system. There is ample opportunity for genetic improvement of the immune capacity because immune traits show substantial genetic variation between pigs. We therefore conclude that indirect selection via immune traits is very interesting, also for practical implementation, and that there is an urgent need for knowledge, within lines, about the genetic relationships between immune capacity traits and resistance to specific diseases or to disease incidence in general. Furthermore, knowledge about the relationship between immune system traits and production traits is needed as well as knowledge about the effect of selection on the epidemiology of disease at a farm/population level and on the host-pathogen interaction and coevolution.

Selection for growth rate or against back fat thickness in pigs is associated with changes in growth hormone axis plasma protein concentration and mRNA level.

Selection for increased growth rate or decreased back fat thickness results in concomitant changes in endocrine and metabolic status. Growth hormone (GH) changes in blood plasma concentration related to selection for growth rate and fat deposition were reported in pigs. The molecular mechanisms regulating selection-induced changes in GH plasma concentration remain largely unknown. We investigated selection-associated changes in GH axis parameters in 2 pig lines selected for increased growth rate (F-line), or decreased back fat thickness (L-line), respectively. First, we investigated selection-associated changes in GH pulse parameters. In both selection lines we found each generation a declining GH peak maximum concentration and area under the GH curve. GH pulse width was not associated with generation number. In both lines generation number was associated with a declined pulse interval, indicating that the number of pulses per day increased on average with 1 pulse per 24 h per generation. Second, plasma concentration of GH axis related Insulin-like growth factor-I (IGF-I) and insulin were investigated. Plasma IGF-I concentration was not associated with generation number in the F-line. Mean plasma insulin concentration declined each generation in both lines. Third, we investigated changes in GH and Pit-1 mRNA levels. In both selection lines GH and Pit-1 mRNA levels increased approximately 50% each generation. The high SD of the GH mRNA levels in both lines may suggest that the GH mRNA levels are pulsatile in vivo. We postulate a molecular mechanism that may explain how selection is associated with increased GH mRNA levels and GH pulse numbers, while lowering GH release per pulse.

Characterization of the innate and adaptive immunity to Salmonella enteritidis PT1 infection in four broiler lines.

Four broiler lines were inoculated orally with Salmonella enteritidis phage type 1 at the age of 7 days (experiment A: lines 1 and 2) and at the age of 1 day (experiment B: lines 3 and 4). At various days post-infection chickens were sacrificed and the number of Salmonella in the caeca, liver, and spleen were determined. Furthermore, phagocytic activity, cellular immune responses, and humoral responses were determined using, respectively, single-cell suspensions of spleen or intestine and serum. In both experiments, similar trends were seen. Increased numbers of S. enteritidis were found in the caeca of lines 1 and 3, whereas at the same time a decreased colonization was found in the spleen and in the liver, as compared to lines 2 and 4. In the latter two lines, the phagocytic activity of the phagocytes was higher and the humoral responses were lower. Observations from this study suggest that lower activity of phagocytes and higher humoral activity prevent systemic S. enteritidis infection.

Genetic regulation of meat production by embryonic muscle formation - a review.

SUMMARY: The biological basis for meat production in livestock animals is localized in the muscles, where lean meat production is under the genetic control of tissue-specific and more ubiquitously operating genes. The muscle tissue-specific MyoD gene family is at the centre of the genetic regulation of myoblast proliferation and differentiation into myofibres. The regulation of embryonic muscle tissue formation (development) by the MyoD genes is duscussed in the context of livestock animals used in meat production. The possibility that the MyoD genes could be useful candidate genes for breeding is discussed. It is concluded that marker assisted selection (MAS) using markers in functional genes is advantageous over MAS using associated markers. ZUSAMMENFASSUNG: Genetische Regulierung der Fleischproduktion bei der embryonalen Muskelbildung - Ein Literaturüberblick Die biologische Grundlage für Fleischproduktion, lokalisiert in den Muskeln, steht unter genetischer Kontrolle durch gewebsspezifische una mehr ubiquitär arbeitende Gene. Die gewebsspezifische MyoD Genfamilie in den Muskeln befindet sich im Zentrum der genetischen Regulierung des Prozesses der Myoblastteilung und Differenzierung zu Myofasern. Die Ubersicht betrifft Regulierung der Bildung des embryonalen Muskelgewebes (Entwicklung) mit Hilfe der MyoD Gene. Die Möglichkeit, daß MyoD Gene erfolgreiche Kandidatengene für Tierzüchtung sein können, wird besprochen. 'Marker-assisted selection' (MAS) mit Hilfe von Markern funktioneller Gene sollte vorteilhafter sein als MAS mit gekoppelten DNA-Sequenzen. RÉSUMÉ: Régulation génétique de la production de viande par la formation embryologique des muscles - un résumé La base biologique de la production de viande dans les animaux d'élevage se situe dans les muscles, là où la production de viande maigre est sous contrôle génétique de gènes générals et tissu-spécifiques. La famille des gènes muscle-spécifiques MyoD forme le centre de la régulation des procès de prolifération des myoblastes et de différenciation vers les myofibres. Le but de cet article rétrospectif est de situer la discussion sur la régulation de la formation embryologique des muscles par les gènes MyoD dans le cadre de l'élevage. La possibilité que les gènes MyoD soient des gènes candidats utiles pour l'élevage sera discutée. La conclusion faite est que 'marker assisted selection' (MAS) en employant des marquers situés dans des gènes fonctionnels a plus d'avantages que MAS avec des marquers associés.

Development of a high capacity radioimmunoassay procedure: ovine follicle stimulating hormone determination in blood plasma as a model.

A sensitive, specific and accurate homologous radioimmunoassay (RIA) for ovine follicle stimulating hormone (oFSH) has been developed, using a [125I]oFSH tracer and a polyclonal rabbit anti-OFSH-serum at a final dilution of 1:224,000. The separation of free and antibody-bound tracer is based on the double antibody solid phase system. The assay was found to be specific for oFSH; cross-reactivity with oLH, oPrl and oGH was lower than 0.2%. The detection limit was 7 pg per tube. Inter- and intra- assay coefficients of variation (CV) were 3.7-8.5% and 6.6%, respectively. The use of a few selfmade appliances in combination with a well-considered time-schedule enabled the processing of three thousand blood plasma samples in triplicate within two weeks. The particular advantage of the method described here is the fast, easy and safe separation of free and antibody-bound tracer with minimal handling of radioactive tubes.

Importance of ewe/lamb relationship and breed in the epidemiology of maedi-visna virus infections.

Sheep from a closed experimental breeding flock containing Finnish Landrace, Ile de France, their F1 crossbreeds, and a new breed were tested for antibodies to maedi-visna virus in 1975 and 1985-86. Over the years, the percentage of seropositive sheep increased: the Ile de France, however, remained virtually negative. Since exposure to the virus was similar, the results indicated a breed-associated difference in susceptibility to maedi-visna virus infection. Analysis of the serological results of 1985-86 yielded a total of 173 dam/progeny pairs. A significant (P less than 0.05) association between the test results of the dams and their progeny was found: seropositive (infected) dams produced 36.6 per cent positive progeny, whereas the seronegative dams had 20.0 per cent positive progeny (odds ratio = 2.3). Further analysis showed that this association was most apparent between dams and their youngest progeny, which is explained by the fact that the chance of infection by horizontal transmission increases with age. These results provide evidence that the ewe/lamb relationship plays a role in the epidemiology of maedi-visna virus infections.