# Effects of Chenopodium album L. Substitution Levels and Harvest Time on In Vitro Rumen Fermentation and Methane Production in Early-Fattening Hanwoo Steers

## TL;DR

This study explores how substituting Chenopodium album L. in Hanwoo steer diets affects rumen fermentation and methane production, finding optimal benefits at 10-15% substitution.

## Contribution

The study introduces Chenopodium album L. as a functional feed ingredient that can reduce methane emissions in ruminants when substituted at moderate levels.

## Key findings

- Supplementing diets with 15% Chenopodium album L. significantly reduced methane production.
- A 10% substitution level optimized fermentation efficiency with the highest volatile fatty acid production.
- August-harvested Chenopodium album L. provided a practical balance of biomass yield and saponins content for methane mitigation.

## Abstract

This study investigated the use of Chenopodium album L. (CAL) in ruminant feed ingredients by evaluating the effects of harvest time and substitution levels on in vitro rumen fermentation. In the first phase, CAL samples harvested from June to August were analyzed for their chemical composition and saponins content, and their impact on fermentation was evaluated. In the second phase, CAL replaced rice straw in a Hanwoo diet at substitution levels of 0%, 5%, 10%, 15%, and 20%, and fermentation characteristics were measured. The results indicated that CAL harvested in July exhibited higher fermentability. However, CAL harvested in August was selected for the subsequent experiment, as it provided a more practical balance of sufficient biomass yield and a higher saponins concentration aligned with the study’s methane mitigation objectives, while also exhibiting a fiber composition comparable to that of rice straw. Supplementing the diet with 15% CAL reduced methane production, likely due to its chemical composition. The highest fermentation efficiency and optimal volatile fatty acid production occurred at a 10% substitution level. These findings suggest that the moderate substitution of CAL (10–15%) in ruminant diets could enhance fermentation efficiency and reduce methane production.

This study investigated the feasibility of incorporating Chenopodium album L. (CAL) into ruminant feed ingredients through 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 saponins 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 the fermentation characteristics. CAL harvested in July exhibited higher fermentability, with total volatile fatty acids (TVFAs) reaching 103.87 mM at 72 h. In contrast, CAL harvested in August showed lower fermentability and digestibility. However, August-harvested CAL was selected for the subsequent experiment, as it provided a more practical balance of sufficient biomass yield and a higher saponins concentration, aligned with the study’s methane mitigation objectives, while also exhibiting a fiber composition comparable to that of rice straw. We hypothesized that the saponins in CAL contribute to methane reductions. Supplementation with 15% of CAL significantly reduced methane production per gram of inoculated and digested dry matter (p < 0.05), likely due to differences in crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and saponins 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. Ammonia–nitrogen production increased from 0 to 3 h, but it continuously decreased between 3 and 9 h due to microbial growth and nitrogen assimilation, as microbes incorporate ammonia into their biomass (p < 0.05). 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 h), confirming a shift toward propionate-based fermentation. Notably, T2 (10% CAL) showed an optimized fermentation efficiency, producing the highest TVFA concentration at 24 h (98.28 mM). These findings highlight the potential for using CAL as a functional feed ingredient, with moderate substitution levels (10–15%) enhancing fermentation efficiency while reducing methane production.