No description available.

No description available.

M.S.

Chickens from lines selected for high (HA) and low (LA) antibody response to sheep red blood cell (SRBC) antigen were Used to study the role of genetic factors involved in resistance to Eimeria tenella and Newcastle disease virus (NDV). Routes of administration were intravenous for SRBC antigen and intranasal for NDV. Chicks were exposed to E. tenella either through a natural challenge via the litter or a controlled oral administration. Differences between lines were observed in resistance to cecal coccidiosis, with line HA chicks being more resistant than those from line LA. Results were similar. for both natural and controlled exposures, Differences in resistance to E. tenella were found among alleles for the I alloystern with degree of additivity from the I⁴ allele on resistance depending on the background genome. Chicks from line HA exhibited higher antibody titers to SRBC and lower titers to NDV than did those from line LA. This pattern was the same regardless of whether antigens were given together or alone. Correlations within lines for birds which received both antigens were positive and significant in line HA and not different from zero in line LA. When NDV was given at the time birds received a booster dose of SRBC, antibody titers for NDV and for primary and booster SRBC were higher in. line HA than line LA. Correlations between all titers were positive and significant in both lines. The data suggest that relationships between titers for SRBC and NDV are influenced by both genetic and nongenetic factors. / M.S.

Experiments were conducted to study the ontogeny, kinetics, and the influence of aflatoxin B1 on antibody response to sheep erythrocyte (SRBC) antigen in White Leghorn chickens. In the first experiment, chickens from the parental lines and reciprocal crosses between them were fed diets containing graded levels, from 0 to 5697 ppb of aflatoxin B₁. Aflatoxin depressed body weights, feed consumption and feed conversion, with feed conversion being depressed less than either body weight or feed consumption. Although there were no differences among aflatoxin levels for body core temperatures, levels of 1830 ppb and higher caused progressive decreases in surface temperatures. Heterophilia, lymphopenia and reduced liver metabolism were observed at the 5697 ppb level. Although bursa and thymus weights were smaller in the aflatoxin-fed birds, there was no reduction in their SRBC antibody levels. The second experiment was designed to measure primary and secondary antibody response to intravenous immunization of SRBC antigen. Treatments included immunization at the dosage of SRBC antigen under which selection was practiced, and higher and lower concentrations. Although the dosage of primary immunization influenced the magnitude of the secondary response within population-primary dosage correlations between peak primary and secondary antibody response were not different from zero. Differences among populations in antibody levels appeared as early as day 4 and persisted until day 24 post-primary immunization. Yet, the general response patterns were the same for all populations with respective peaks occurring at the same time. The ontogeny of post-hatching production of antibody SRBC antigen and growth of bursa, thymus and spleen were measured in the third experiment. Both parental lines and reciprocal crosses between them reached serological maturity by 14 days of age. By 7 days, there were differences among populations for frequency of responders to SRBC antigen and magnitude of titers, inferring genetic variation for both the event and subsequent levels of antibody production. / Ph. D.

The effects of vitamin E (VE) and Arginine (ARG) on humoral and cellular immunity in chickens were investigated in two experiments. The humoral immunity was measured by antibody responses to sheep red blood cells (SRBC) and maternal antibody titers to the infectious bursal disease virus (IBDV), while the cellular immunity was studied using the cutaneous basophil hypersensitivity test to phytogemagglutinin (PHA) and by counting subpopulations of T-lymphocytes. We used two levels of ARG: normal (NARG, 1.2% in feed) and high ARG (HARG, additional 0.3% in drinking water or 1% in feed in experiments 1 and 2, respectively); and three levels of VE were given: 40, 80, and 400 IU/kg feed in experiment 1, and 40, 80, and 200 in experiment 2. / HARG improved the antibody response to SRBC compared with NARG ( P<0.01 for experiment 1 and P<0.013 for experiment 2) 4 days after injection in both experiments. In experiment 1, the VE80 birds maintained higher antibody titers to SRBC (P<0.001) than the VE40 and VE400 birds 4, 8 and 16 d after inoculation. In experiment 2, the antibody titers to SRBC were higher in the VE80 birds compared with the VE200 birds at days 5, 8, and 12 after inoculation (P<0.001). Maternal antibody titers (log10) to the IBDV were higher in the HARG than in the NARG diet in 17-day-old birds (P<0.001) and higher in the VE80 than in the VE40 birds (P<0.001), yet similar to those of the VE200 birds. No interactions were found between ARG and VE. / Naive birds fed HARG exhibited a higher response than NARG birds (P<0.05) to PHA-P at d 17 and to PHA-M at d 41, but, after a second exposure, high ARG levels did not have an effect. Also, in naive birds, the effects of VE were not significant at d 17, but showed an influence after a second exposure in 41-d-old birds. / The percentage of T-helper (Th) and T-cytotoxic (Tc) cells in the blood of 29-d-old birds were not different between ARG levels (P=0.07 and P=0.06, respectively), but Th cells were higher in the VE80 and VE200 birds than in the VE40 birds, and Tc was higher in the VE80 than in the VE40 birds (P=0.02). The B-cell:T-cell ratio was higher in the HARG than the NARG birds (P=0.01) and in the VE40 compared with the VE80 and VE200 birds (P<0.001). Neither ARG nor VE had an effect on the ratio of Th:Tc cells, nor on the percentage of immature T-lymphocytes. / A combination of high levels of ARG and high levels of VE (80 IU/kg of BW) has an important immunomodulation effect on the cellular and humoral immune responses in broiler chickens, improving both maternal antibody titers against the IBDV and antibody titers against SRBC. A combination of ARG and VE increases the proportions of Th and Tc cells, the B-cell:T-cell ratio, and growth performance. The evidence suggests that ARG and VE play complementary and regulatory role on immune response and may enhance the resistance of broilers to infectious diseases. / Key words. Arginine, vitamin E, humoral immunity, cell-mediated immunity, lymphocyte, ELISA. / L'effet de la vitamine E (VE) et l'arginine (ARG) sur les systèmes hummoraireet cellulaire de l'immunité a était évalué chez la volaille dans deux recherches. Lesystème hummoraire de l'immunité a était évalué en utilisant les paramètres tels que laproduction d'anticorps après une injection des globules rouge provenant des moutons(SRBC) et le niveau d'anticorps maternelle après une infection avec les virus causantla maladie 'infectious bursal disease' (lBDV), tandis que les effets sur le systemcellulaire de l'immunité avaient aussi été évalués en utilisant les paramètres comme'cutaneous basophil hypersensitivity test to phytogemagglutinin (PHA)' et endéterminant la concentration des lymphocytes T. Deux concentrations de ARG avaientété utilisées: normale (NARG, 1.2 % de la diète) et une concentration élevée (HARG,additionel 0.3 % dans l'eau ou 1 % dans les diètes); et 3 concentrations de VE: 40, 80et 400 lU/kg dans les diètes dans la première recherche et 40, 80, et 200 lU/kg dans ladeuxième recherche.

No description available.

Graduation date: 1992

Production traits and disease resistance are believed to be under the control of many genes, i.e. quantitative trait loci (QTL). The objective of the present study was to establish a methodology for identifying DNA markers which are associated with QTL in chickens using an alternative approach to the traditional linkage analysis. A systematic screening approach was designed to search a chicken liver cDNA library for clones which revealed polymorphisms associated with traits. In the first stage of the experiment, a total of 92 cDNA clones were subjected to restriction fragment length polymorphism (RFLP) analysis. About 33% and 22% of the clones revealed DNA polymorphisms at MspI and TaqI restriction sites, respectively. Subsequently, DNA polymorphisms which responded to selection were identified by comparing RFLP frequencies in divergently selected strains of chickens. About 60% of the RFLPs responded to selection for egg production traits and/or Marek's disease (MD) resistance. Trait associations of these RFLPs were then studied by selectively genotyping individuals at the extremes of trait distributions, followed by an analysis of individuals in the entire population and statistical evaluation. Finally, RFLP regions of DNA markers were characterized and PCR assays for rapid RFLP screening were developed. DNA markers in two genes were identified and characterized by this methodology. One was a marker in the chicken mitochondrial genome which arose from a nucleotide substitution (T to C) in the NADH subunit IV gene. Statistical analysis for typing random individual samples from the strains showed that this DNA polymorphism was associated with mature body weight and egg specific gravity which is a strong indicator for egg shell thickness. Other analyzed markers were located in the chicken mitochondrial phospho-enolpyruvate carboxykinase (PEPCK-M). Using the cDNA of this gene as a probe, southern blotting revealed a highly polymorphic band pattern. Statistical analy

Two experiments were conducted to evaluate the effects of arginine, vitamin E, and their combination on cardiopulmonary performance and nitric oxide synthase (NOS) activity in broilers undergoing cold-induced ascites (pulmonary hypertension) after an acute challenge with epinephrine. One day-old male broilers ( n = 25/treatment) were supplemented with arginine (0.3% water supplementation), vitamin E (400 IU/L or kg, water or feed supplementation; experiment 1 and 2 respectively) or both compounds, above NRC (1994) recommendations. From day 28 to 42, a catheterization was performed (n = 8/treatment) to evaluate pulmonary and mean arterial pressures, and heart rate. After recording baseline values, two injections of epinephrine (1 or 0.5 mg/kg body weight, experiment 1 and 2, respectively) were administered in a 20 min interval. The NOS activity was estimated through the conversion of 14C-arginine to 14C-citrulline in isolated pulmonary arteries ( n = 8/treatment). Overall, the time taken for pulmonary arterial pressure to return to values no different from initial baseline levels was longer for the birds consuming high levels of vitamin E (alone or in combination with arginine) compared to birds supplemented only with arginine. Although NOS activity was highly variable, birds fed with high arginine levels tended to have the lowest NOS activity. These results showed that vitamin E supplementation at the levels used in these experiments has detrimental effects on cardiopulmonary performance, and does not improve NOS activity in isolated pulmonary arteries.