Sustainability of Using Cress Seed as a Feed Additive: Effects on In Vitro Gas Production, Methane Emissions, and Rumen Fermentation

This study investigated the sustainable effects of incorporating graded levels of dried cress seeds [Lepidium sativum; 0, 0.5, 1.0, 1.5, and 2.0% dry matter (DM) basis] into a total mixed ration (TMR) containing 500 g concentrate mixture, 400 g berseem hay, and 100 g rice straw on in vitro ruminal gas production (GP), methane (CH4) and carbon dioxide (CO2) kinetics, nutrient degradability, and fermentation characteristics. Gas chromatography–mass spectrometry analysis identified a complex volatile profile in cress seeds dominated by 1,8-cineole (61.8%), estragole (15.1%), fenchone (7.71%), and pinenes, compounds known for antimicrobial and rumen-modulating properties. In vitro fermentation results showed a quadratic increase with cress seeds inclusion (p < 0.01) in GP parameters by 50.2%, from 78.1 to 117.3 mL/g DM, while the GP rate decreased with cress seeds inclusion by 9.2% (p = 0.007). Methane production linearly increased by 38.1% (p = 0.006) but the CH4 production rate declined by 34.3% (p = 0.026), leading to a 20.8% linear reduction (p = 0.002) in CH4 proportion relative to total gas, indicating improved fermentation efficiency and CH4 mitigation. CO2 production parameters quadratically increased, with asymptote rising by 42.2% (p < 0.01) and rate by 50.0% (p = 0.005). Nutrient degradability was markedly enhanced with cress seed inclusion. DM degradability quadratically increased by 38.7% (p = 0.041), neutral detergent fiber (NDF) degradability by 39.9% (p < 0.001), and acid detergent fiber (ADF) degradability by 43.6% (p < 0.001). Total volatile fatty acids (VFAs) linearly increased by 29.5% (p < 0.001), with acetate and propionate concentrations rising linearly by 36.0% (p < 0.001) and 23.9% (p = 0.002), respectively, while the acetate-to-propionate ratio remained stable (p = 0.397). Metabolizable energy (ME) improved quadratically by 18.6% (p = 0.003), and microbial crude protein (MCP) production linearly increased by 36.6% (p < 0.001). Ruminal pH and ammonia nitrogen concentrations remained unaffected. As a conclusion, dietary inclusion of dried cress seeds up to 2% of the diet enhances ruminal fermentation efficiency and nutrient degradability, reduces CH4intensity, and stimulates microbial protein synthesis, highlighting its potential as a natural feed additive to improve ruminant productivity and reduce greenhouse gas emissions.