In Vitro Evaluation of <i>Chenopodium album</i> L. as a Ruminant Feed Ingredient: Influence of Harvest Time and Substitution Levels on Fermentation and Methane Reduction

This study investigated the feasibility of incorporating Chenopodium album L (CAL) into ruminant feed ingredients by evaluating the effects of harvest time and substitution levels on in vitro rumen fermentation. In the first phase, a sole-substrate experiment was conducted using CAL harvested from June to August, analyzing its chemical composition and total saponin content. The impact of harvest time on fermentation parameters was assessed with CAL as the sole substrate. The second phase involved a mixed-substrate experiment using an early-fattening Hanwoo diet (30% rice straw and 70% concentrate), where increasing proportions of CAL (Control: 0%, T1: 5%, T2: 10%, T3: 15%, and T4: 20%) replaced rice straw. Seasonal variations in CAL composition influenced fermentation characteristics, with July-harvested CAL exhibiting higher fermentability, while August-harvested CAL had lower fermentability. However, August-harvested CAL was selected for the second experiment due to its greater availability. We hypothesized that saponins in CAL contribute to methane reduction. Supplementation with 15% of CAL significantly reduced methane production per gram of digested substrate (p &amp;lt; 0.05), likely due to differences in crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and saponin content. However, despite having the lowest fiber content, T4 (20% CAL) exhibited the lowest in vitro dry matter digestibility (IVDMD), suggesting that factors such as saponins, CAL’s chemical composition, or microbial shifts may have hindered digestibility. Fermentation characteristics further revealed that the acetate-to-propionate (A/P) ratio decreased with increasing CAL levels, with T4 showing the lowest ratio (1.55 at 72 hours), confirming a shift toward propionate-based fermentation. Notably, T2 (10% CAL) optimized fermentation efficiency, producing the highest total volatile fatty acid (VFA) concentration at 24 hours (98.28 mM). These findings highlight the potential of CAL as a functional feed ingredient, with moderate substitution levels (10–15%) enhancing fermentation efficiency while reducing methane production.