Sesame seed meal as a partial soybean meal substitute in ruminant diets: effects on rumen fermentation, nutrient...

This study investigated the effects of replacing soybean meal (SBM) with sesame seed meal (SSM) on in vitro ruminal fermentation and methane (CH₄) and carbon dioxide (CO₂) production using the ANKOM RF system for 48 h. Five total mixed rations were formulated, in which SBM was progressively substituted with SSM at 0, 25, 50, 75, and 100% of the concentrate protein, corresponding to dietary SSM inclusions of 0, 3.3, 6.6, 9.8, and 13.1% of DM. Results showed that partial replacement at the 25% level enhanced fermentation efficiency, significantly (P < 0.05) increasing asymptotic gas production, fractional gas production rate, metabolizable energy (ME), and DM degradability compared with the control. Conversely, higher substitution levels progressively reduced fermentation. Fiber degradability was particularly affected, with neutral detergent fiber and acid detergent fiber degradability declining as SSM inclusion increased (P = 0.002). Total volatile fatty acid (VFA) concentrations and individual VFA fractions also decreased significantly at higher SSM levels (P < 0.01), while ammonia nitrogen concentration declined linearly with increasing SSM (P = 0.007). Methane production was slightly elevated at the lowest SSM inclusion but declined substantially at higher substitution levels (P < 0.01). In contrast, the proportion of CO₂ in total gas increased with higher SSM inclusion (P < 0.001). These findings indicate that SSM can partially replace SBM (up to 25% of the concentrate protein) without compromising ruminal fermentation or nutrient degradability. Higher inclusion levels; however, reduce fermentative activity and fiber degradability while lowering CH₄ emissions, highlighting the potential environmental benefits of incorporating this oilseed by-product into ruminant feeding strategies.