PS10-20. Effect of Sesame Plant Silage Level on In Vitro Digestibility, Ruminal Fermentation, and Methane Production.

Abstract The objective was to evaluate the inclusion of sesame plant silage (SPS) in a tropical grass-based diet using an in vitro gas production test, determining in vitro dry matter digestibility (IVDMD) and methane gas production. The base diet was Brachiaria sp. hay, with SPS substituted at 0%, 20%, 40%, 60%, 80%, and 100%. 0.5 g of substrate was placed in 4 x 10 cm nylon bags with 24 µm pores. These bags were deposited into 120 mL amber bottles. A completely randomized block design was used, with three flasks (replicates) per experimental treatment and per incubation, over three runs (blocks). Rumen contents were obtained from four Holstein cows and filtered through four layers of gauze. The rumen fluid was mixed with buffer according to the method of Menke and Steingass (1988). The flasks were placed in a 39 °C water bath. Gas production and pressure were recorded at 0, 3, 6, 9, 12, 18, 24, 36, 42, 48, and 72 hours using a digital manometer (Traceable®, Fisher Scientific). Gas samples were collected using a 50 mL syringe and transferred to vacuum flasks for later methane determination using an infrared detector (Gas-Pro Crowcon). Samples were analyzed for NH3-N and volatile fatty acids (VFAs) by gas chromatography. Fermentation kinetics were obtained by converting gas pressure to volume using the equation y = 7.0245x - 1.0849 (R² = 0.989), where y is gas volume and x is gas pressure (PSI). The fractional degradation rate (S, h), lag phase, and maximum gas production volume (Vmax) were calculated. Data were analyzed with a randomized complete block design in SAS MIXED. Mean comparisons used Tukey's test and orthogonal polynomials for the SPS level. For fermentation kinetics and IVDMD (Table 1), increasing SPS inclusion increased IVDMD up to 80% (quadratic effect, p < 0.01), after which it decreased. Vmax decreased (linear effect, P < 0.01) and S increased (linear effect, P < 0.01) as SPS increased. Table 2 shows that increasing SPS resulted in a linear decrease (P < 0.05) in all methane variables, reaching a 50% reduction at 100% SPS. This is mainly due to the sesame plant's oil content of 14% (DB). The IVDMD improves to 80% SPS, resulting in a 32% reduction in methane. Therefore, SPS offers a sustainable alternative in tropical areas for improving dietary digestibility and reducing methane emissions. This study was partially funded by the PAPIIT TA200625 project of the DGAPA, UNAM. For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text.