The effect of DL-, L-isomers and DL-hydroxy analog administered at 2 levels as dietary sources of methionine on the metabolic and antioxidant parameters and growth performance of turkeys.

A hypothesis was verified that dietary methionine (Met) improves the growth and antioxidant status of turkeys, and that its effects depend on dietary inclusion levels and sources. A total of 816 female Hybrid Converter turkeys was fed wheat-soybean meal-based diets supplemented with 3 sources of Met: DL-, L-isomers and DL-hydroxy analog (DLM, LM, and MHA, respectively). In 4 4-week periods (from one to 16 wk of age), dietary Met content corresponded to NRC (1994) recommendations or was increased by approximately 50% (in one to 8 wk by 44 to 46% and in 9 to 16 wk by 55 to 56% vs. the NRC guidelines) to match the recommendations of some breeding companies. Increased Met content resulted in higher final body weights of turkeys (P = 0.002), an improved feed conversion ratio (P = 0.049), increased total glutathione concentration and ferric reducing ability of plasma (FRAP) values, and decreased malondialdehyde (MDA) concentration (all P < 0.001) in the blood plasma of turkeys. In comparison with DLM, LM and MHA contributed to an increase in plasma glutathione concentration (P = 0.001), a decrease in plasma triacylglycerol (P = 0.003) and uric acid (P = 0.001) concentrations, and a decrease in liver MDA (P = 0.001) levels. A decrease in plasma MDA (vs. DLM) and lipid peroxides (LOOH) (vs. DLM and LM) concentrations as well as a decrease in plasma superoxide dismutase (SOD) activity (vs. DLM and LM) also were noted in the MHA treatment (P = 0.016, P = 0.001 and P = 0.011, respectively). In conclusion, the results of the study indicate that the antioxidant status of turkeys could be affected by dietary Met levels and sources. The dietary Met content increased by 50% relative to NRC recommendations, improved the growth performance of turkeys, and strengthened their antioxidant defense system. In comparison with DLM, LM and MHA could be considered positive nutritional factors as manifested by a beneficial decrease in plasma and hepatic MDA concentrations as well as an increase in plasma glutathione levels, and the effect of MHA was more pronounced.

Effect of different dietary methionine levels on the growth performance and tissue redox parameters of turkeys.

A total of 630 8-week-old female Hybrid Converter turkeys were divided (based on their body weights) into 6 groups, with 7 replicates per group and 15 birds per replicate. All birds were fed identical isocaloric and isonitrogenous wheat-soybean meal-based diets without (group 1) or with (groups 2 to 6) increasing levels of supplemental methionine (Met). The total content of Met in diets 1 to 6 was as follows (%): 0.29, 0.32, 0.40, 0.47, 0.56, and 0.61 at 9 to 12 wk of age and 0.24, 0.28, 0.34, 0.42, 0.47, and 0.55 at 13 to 16 wk of age. In both feeding phases, dietary Met levels in group 3 corresponded to those recommended by the National Research Council (NRC) (1994). Different dietary Met concentrations had no influence on feed intake, the final body weights of turkeys or carcass dressing percentage. Only in the first experimental feeding period (9 to 12 wk), the lowest dietary Met content significantly deteriorated the feed conversion ratio (FCR), whereas the highest Met content led to a significant improvement in FCR. After 8 wk of experimental feeding, dietary treatment 1 contributed to a significant increase in the activity of catalase (CAT) (blood and breast muscles) and superoxide dismutase (liver), an increase in lipid peroxides concentrations (blood, breast muscle) and a decrease in total glutathione (GSH+GSSG) content (breast muscles), in comparison to treatment 3 which is comparable to NRC recommendations. The highest level of dietary Met significantly increased blood total antioxidant potential (FRAP) values and glutathione content in the liver. To sum up, in the final feeding period between 9 and 16 wk of age, the growth performance of female turkeys was not deteriorated by dietary Met deficiency or excess (-30% and up to +50% relative to NRC recommendations, respectively). The total antioxidant potential can be effectively increased by dietary Met supplementation, but the highest Met level may lead to unbalanced oxidative changes in the body as indicated by lower FRAP values and a lower GSH/GSSG ratio in the liver.

Tumor necrosis factor-alpha (TNFα) gene polymorphism and expression of membrane-bound TNFα protein on CD11b+ and IgM+ cells in cows naturally infected with bovine leukemia virus.

The aim of this study was to determine whether SNP at position -824 (promoter region) of the TNFα gene significantly differentiates the size of IgM+, CD5+ and CD11b+ cell subpopulations and affects the expression of membrane-bound TNFα protein (mTNFα) on these cells and their susceptibility to BLV infections. In this study, significant differences were determined for the first time between TNFα genotypes and the percentage of cells with the CD11b+TNFα+p24+ immunophenotype. Furthermore, greater expansion of lymphocytes with the IgM+TNFα+p24+ immunophenotype was reported in cows with the G/G genotype than in A/A homozygotes. Cells with the above immunophenotype were more frequently observed in cows with persistent leukocytosis than in aleukemic cattle. Our results suggest that polymorphism of the TNFα-824 A>G gene and mTNFα protein expression play an important role in the pathogenesis of enzootic bovine leukosis.

Biochemical and immunological responses of young turkeys to vaccination against Ornithobacterium rhinotraheale and different levels of dietary methionine.

The objective of this study was to verify the hypothesis that increasing levels of dietary methionine can stimulate the mechanisms of cell-mediated and humoral immunity in young turkeys. The blood and organs involved in cell-mediated and humoral immune responses were analyzed in 8-week-old turkeys that had been vaccinated against Ornithobacterium rhinotraheale (ORT) infection (on days 17 and 48). The birds were fed diets with a low (LM), medium (MM) and high (HM) methionine content (0.45 and 0.40%, 0.60 and 0.51%, 0.71 and 0.57% in weeks 1 - 4 and 5 - 8, respectively). Dietary methionine supplementation led to a significant increase in body weights of turkeys at 56 days of age, from 3532 g in group LM to 3720 g in group MM and 3760 g in group HM (p=0.001). A significant increase in vaccine-induced antibody titers against ORT was noted in group HM relative to group LM (p=0.006). Increasing levels of methionine had no significant effect on total serum IgG nor IgM levels and most serum biochemical parameters, TP, ALB, GLOB, GLU, AST, ALP, P and Ca. In comparison with group LM, group HM turkeys were characterized by a lower percentage of IgM⁺ B cell subpopulation in the blood and bursa of Fabricius. The percentages of CD4⁺ and CD8⁺ T cell subpopulations in the bursa of Fabricius in group HM were significantly different from those found in groups LM and MM. The highest percentages of CD4⁺ T cells and CD8⁺ T cells in the spleen were observed in groups LM (p<0.001) and HM (p=0.04), respectively. The differences were statistically significant relative to the remaining groups. Turkeys of group LM were characterized by a lower CD4⁺ T cell percentage in the thymus (p<0.001) and a lower CD8⁺ T cell percentage in the cecal tonsils (CTs) (p<0.01). Vaccination against ORT resulted in a significant increase in the percentage of CD4⁺CD8⁺ T cell subpopulation and a decrease in the percentage of CD8⁺ T cell subset in the spleen.

Immunological and biochemical indicators in turkeys fed diets with a different Methionine content.

The objective of this study was to determine the effect of different levels of dietary methionine on selected immune parameters of young turkeys. A total of 357 one-day-old female Hybrid Converter turkeys were randomly divided into three groups with low, medium and high level of dietary me- thionine (LM, MM, HM) of seven replicates each. Methionine was added to the basal diet (LM) at 0.16% (MM) and 0.32% (HM). At 17 days of age, seven birds per group were vaccinated against Ornithobacterium rhinotraheale (ORT) infection, with ORNITIN (ABIC) vaccine. At 28 days of age, blood was sampled and the birds were euthanized. The serum concentrations and activity of selected biochemical parameters, total IgY and IgM, and vaccine-induced antibody titers (IgY) against ORT were determined. The percentages of CD4+, CD8+, CD4+/CD8+ T cell subpopulations and IgM+ B cell subpopulation were determined in blood and organs by flow cytometry. Different supplementary levels of methionine had no significant effect on vaccine-induced anti- body titers against ORT or total serum IgM and IgY levels, as well as on the percentages of periph- eral blood T and B cell subsets. Increasing dietary methionine rates decreased the percentage of CD4+ T cell subpopulation, however it has increased the percentage of IgM+ B cell subpopulation in the spleen. Vaccination against ORT resulted in a significant decrease in the percentage of CD4+ T cell subset and an increase in the percentage of CD8+ T cell subset in the spleen. It could be concluded that MM turkeys have developed the most desirable values of immune parameters.