# Comparative Evaluation of Crushed Almonds, Peanut Skins, and Water Hyacinth as Alternative Feed Resources for Ruminants: Fermentation Responses and Methane Mitigation Potential

## TL;DR

This paper evaluates crushed almonds, peanut skins, and water hyacinth as alternative ruminant feeds, finding that peanut skins significantly reduce methane emissions.

## Contribution

The study introduces peanut skins as a promising feed additive for methane mitigation in ruminant diets.

## Key findings

- Peanut skins reduced methane emissions by 57% when replacing grass hay.
- Crushed almonds improved digestibility but increased methane emissions by 12%.
- Water hyacinth showed moderate methane reduction (14%) and low digestibility.

## Abstract

Livestock production systems are under pressure to deliver affordable feeds that sustain productivity while reducing greenhouse gas emissions. This study examined three unconventional feed and food by-products—crushed almonds, peanut skins, and water hyacinth—as feed additives and grass hay substitutes in ruminant diets. Almonds, with high energy and low fiber content, improved digestibility and fermentation but increased methane emissions, indicating both benefits and drawbacks. Peanut skins, a common agricultural by-product, reduced methane emissions by more than half, although digestibility declined at higher inclusion levels. Water hyacinth maintained digestibility similar to that of grass hay but showed comparatively limited fermentation activity. These findings suggest that these agricultural residues, especially peanut skins, could help pastoral farming systems and reduce methane emissions while partially replacing grass hay. Further animal trials and economic evaluations are required to confirm the practical implications; however, these resources hold promise for climate-smart animal agriculture.

Agro-residues and aquatic biomass are potential sustainable ruminant feeds. However, their effects on rumen digestibility, fermentation, and greenhouse gas emissions remain insufficiently characterized. This study used two in vitro batch culture experiments to evaluate crushed almonds, peanut skins, and water hyacinth as feed additives (1–10%) and grass hay replacements (25–100%). Their chemical composition varied significantly. Crushed almonds are rich in crude protein (22.47%) and ether extract (38.38%). Peanut skins contained moderate protein (13.87%) and high fiber and lignin, while water hyacinth had the lowest protein (7.27%) and highest fiber and ash fractions. All ingredients had no effect on fermentation or methane production when used as additives, whereas grass hay replacement induced marked ingredient-specific responses. Crushed almonds showed the highest in vitro dry matter digestibility (IVDMD), increased propionate, and lowered the A:P ratio; however, methane production increased by 12%. Peanut skins sharply reduced IVDMD with increasing inclusion, resulting in the strongest methane mitigation (57% reduction). Water hyacinth displayed a modestly low IVDMD and moderate methane reduction (14%). In conclusion, methane production is closely associated with substrate degradability, and each ingredient exhibits distinct functional tendencies: crushed almonds enhanced energy availability and digestibility, peanut skins showed methane mitigation potential, and water hyacinth functioned primarily as a low-fermentability grass hay substitute.