Enhanced ruminant nutrition and greenhouse gas abatement using coensiled corn silage, oilseeds, and spent mushroom substrate

This study aimed to enhance feed efficiency and mitigate greenhouse gas emissions in ruminants by co-ensiling spent mushroom substrate (SMS) and oilseeds (OS; a 1:1 ratio of canola and soybean seeds) with corn silage (CS). Treatments represented varying inclusion levels (%) of CS, SMS, and OS as follows (CS:SMS: OS): Control=100:0:0, T1=90:5:5, T2=80:10:10, T3=70:15:15, T4=60:20:20, and T5=50:25:25. Each treatment was ensiled for 0, 21, 42, or 63 days. A highly significant interaction between treatment and ensiling duration was noted for most chemical components (p<0.001), with crude protein, ether extract, and ash increasing, and neutral detergent fiber (NDF), acid detergent fiber (ADF), and nonfibrous carbohydrates decreasing with increasing SMS and OS levels (p<0.001). Acid detergent lignin (ADL), cellulose, and hemicellulose also varied significantly with treatment-time interactions (p<0.05). Gas production, including methane, carbon dioxide, and hydrogen sulfide (H2S), was influenced by both treatment and ensiling duration, with an interaction effect (p<0.05). At 42 days, H2S increased by 38.3% compared to the control. Methane declined linearly (p<0.001), and H2S followed linear (p=0.016) and quadratic (p=0.001) trends. Total volatile fatty acids were unaffected by treatment (p = 0.123), but ensiling time influenced the proportions of acetate (p=0.002), propionate (p=0.001), butyrate (p<0.001), and valerate (p<0.001). At 42 days, acetate and valerate increased by 3.1% and 8.1%, respectively, while propionate and butyrate decreased by 5.5% and 4.9%, respectively, compared to the control. Nutrient degradability and microbial mass (MM) showed significant treatment and time interactions [p=0.002 for MM, in vitro apparent degradable dry matter (IVADDM), and partitioning factor (PF)], with ADL degradability increasing by 77.7% and DM degradability by 10.7%. In comparison, IVADDM and MM decreased by 6.4% and 70.6%, respectively, in T3 after 42 days. Ensiling time enhanced DM degradability (p<0.001), IVADDM (p<0.001), and MM (p<0.001), while in vitro true degradable DM and PF were not affected (p>0.05). The most favorable balance between digestibility, MM, and reduced emissions was achieved with treatment T3, which was ensiled for 42 days. In conclusion, co-ensiling moderate levels of SMS and OS with CS for 42 days is recommended to improve feed quality and reduce the environmental impact of ruminant production.