In vitro ruminal degradation of neutral detergent fiber insoluble protein from tropical pastures fertilized with nitrogen

The objective was to determine in vitro the NDF insoluble protein (NDIP) extension and degradation rate of four tropical grasses by the potential effect of N fertilization. The grasses (Andropogon gayanus, Brachiaria brizantha, Cynodon plectostachyus and Megathyrsus maximus) that grow in Mexico were used. Each grass was grown in four plots (5×5 m), fertilized (relationship equivalent to 0 and 100 kg N/ha) and clipped 35 d after the N fertilization. A complete randomized block design with factorial arrangement 4×2, and two replicates per treatment was used, where the factors were grass species and N fertilization. Non-protein nitrogen (NPN), buffer insoluble protein (IP), NDIP and acid detergent insoluble protein (ADIP) were performed. Freeze-dried samples were incubated at 0, 1.5, 3, 6, 9, 12, 24, 48 and 96 h. After fermentation, the CP content of the NDF residues was determined. An exponential equation was used to determine the rate of the NDIP disappearance. There was no detectable interaction between type of grass and fertilization level. The NDIP (as %CP) averaged 35 % with a range of 10 to 60 %. The NDIP variation was primarily due to species. The extent and rates of degradation of the NDIP were 70.6 % and 7.1 %/h respectively, with no N-fertilization effect. The NDIP was degraded faster (P≤0.05) than NDF (7.7 vs 5.0 %/h). These data show that the NDIP is ruminally degraded and that this fraction significantly contributes to the rumen nitrogen supply

In vitro ruminal degradation of carbohydrate fractions in tropical grasses fertilized with nitrogen

The goal was to determine the digestion rates of carbohydrate fractions A (sugars, oligosaccharides and organic acids), B1 (starch and soluble fiber), NSC (non-structural carbohydrates) and B2 (available NDF) in four tropical grasses using the gas production technique. Samples of whole forage (WF), residue insoluble in 90% ethanol (EIR) and isolated NDF (iNDF) were fermented in vitro and gas production measured. Gas volumes were determined from the following fractions, A = WF minus EIR; B1 = EIR - ND; NSC = WF - iNDF; and B2 = iNDF. Grasses were Andropogon gayanus, Urochloa brizantha, Cynodon plectostachyus, and Megathyrsus maximus each grown in Veracruz, Mexico on four plots (5×5 m), fertilized (relationship equivalent to 0 and 100 kg N/ha) and clipped 35 d after the N fertilization. A complete randomized block design with factorial arrangement 4×2 and two replicates per treatment was used. Factors were grass species and N fertilization. Data were fit using a single-pool exponential model with lag. The volume (mL gas/100 mg OM), rate (%/h) and lag (h) were: WF (22.8; 5.3; 2.1); A (3.2; 15.7; 0.5); B1 (1.5; 15.7; 0.2); and B2 (18.3; 6.6; 5.2). Andropogon and Urochloa had higher NSC content compared to Megathyrsus and Cynodon but lower gas yield per unit of NSC. Rates of digestion for the B2 fraction ranged from 4 to 8 %/h; and NSC digestion rate averaged 15.7 %/h. Nitrogen fertilization reduced carbohydrate pool sizes but did not affect rates of digestion. It is concluded that the rates of digestion of the carbohydrate fractions differs by grass specie.Our goal was to determine the digestion rates of carbohydrate fractions A (sugars, oligosaccharides and organic acids), B1 (starch and soluble fiber), NSC (non-structural carbohydrates) and B2 (available NDF) in four tropical grasses using the gas production technique. Samples of whole forage (WF), residue insoluble in 90% ethanol (EIR) and isolated NDF (ND) were fermented in vitro and gas production measured. Gas volumes determined from the following fractions, A = WF minus EIR; B1 = EIR - ND; NSC = WF - ND; and B2 = ND.  Grasses were Andropogon gayanus, Urochloa brizantha, Cynodon plectostachyus, and Megathyrsus maximum each grown in Veracruz, Mexico on four plots (5×5 m), fertilized (relationship equivalent to 0 and 100 kg N/ha) and clipped 35 d after the N fertilization. A complete randomized block design with factorial arrangement 4×2 and two replicates per treatment was used. Factors were grass species and N fertilization. Data were fit using a single-pool exponential model with lag. The volume (mL gas/100 mg OM), rate (%/h) and lag (h) were: WF (22.8; 5.3; 2.1); A (3.2; 15.7; 0.5); B1 (1.5; 15.7; 0.2); and B2 (18.3; 6.6; 5.2). Andropogon and Urochloa had higher NSC content compared to Megathyrsus and Cynodon but lower gas yield per unit of NSC. Rates of digestion for the B2 fraction ranged from 4 to 8 %/h; and NSC digestion rate averaged 15.7 %/h. Nitrogen fertilization reduced carbohydrate pool sizes but did not affect rates of digestion. It is concluded that ruminally available energy from SC and NSC in tropical forages should be revised more extensively

OVX836 Heptameric Nucleoprotein Vaccine Generates Lung Tissue-Resident Memory CD8+ T-Cells for Cross-Protection Against Influenza

International audienceTissue-resident memory (TRM) CD8+ T-cells play a crucial role in the protection against influenza infection but remain difficult to elicit using recombinant protein vaccines. OVX836 is a recombinant protein vaccine, obtained by the fusion of the DNA sequence of the influenza A nucleoprotein (NP) to the DNA sequence of the OVX313 heptamerization domain. We previously demonstrated that OVX836 provides broad-spectrum protection against influenza viruses. Here, we show that OVX836 intramuscular (IM) immunization induces higher numbers of NP-specific IFNg-producing CD8+ T-cells in the lung, compared to mutant NP (NPm) and wild-type NP (NPwt), which form monomeric and trimeric structures, respectively. OVX836 induces cytotoxic CD8+ T-cells and high frequencies of lung TRM CD8+ T-cells, while inducing solid protection against lethal influenza virus challenges for at least 90 days. Adoptive transfer experiments demonstrated that protection against diverse influenza subtypes is mediated by NPspecific CD8+ T-cells isolated from the lung and spleen following OVX836 vaccination. OVX836 induces a high number of NP-specific lung CD8+ TRM-cells for long-term protection against influenza viruses