# Phytochemicals in Ruminant Diets: Mechanistic Insights, Product Quality Enhancement, and Pathways to Sustainable Milk and Meat Production—Invited Review

## TL;DR

This review explores how adding plant-based chemicals to ruminant diets can improve animal health, meat and milk quality, and environmental sustainability.

## Contribution

The paper provides a comprehensive synthesis of the mechanisms and benefits of dietary phytochemicals in sustainable ruminant production.

## Key findings

- Phytochemicals improve feed efficiency and reduce methane and nitrogen emissions in ruminants.
- They enhance milk and meat quality by increasing healthy fats and antioxidants.
- Phytogenic feedstuffs support sustainable livestock systems by reducing reliance on synthetic additives.

## Abstract

Ruminant animals such as cows, goats, and sheep play an important role in providing milk and meat for people around the world. Today, farmers and scientists are looking for natural ways to improve animal health, increase productivity, and reduce environmental problems that are often linked with livestock production systems. Many plants contain phytochemicals that can support these goals. When animals eat herbs, spices, grasses or legumes rich in phytochemicals, their digestion may become efficient, helping them get more nutrients from the same feed. These natural bioactive compounds can also reduce oxidative stress, methane production and nitrogenous emissions in livestock systems. As a result, animals may produce nutritious milk and meat with healthier fats, more antioxidants, and better flavor and shelf life with minimal impact on the environment. Overall, dietary phytochemicals offer a promising sustainable way to improve milk and meat production and quality while supporting animal health and reducing environmental impact.

Dietary phytochemicals, primarily derived from grasses, legumes, and agro-industrial byproducts of plant origin, encompass distinct chemical classes such as polyphenols (including tannins, flavonoids, and other polyphenol compounds), saponins, organosulfur compounds, and essential oils (largely composed of terpenoids and phenylpropanoids). These compounds can function as rumen modifiers, antimethanogenic agents, anthelmintics, growth promoters, stress mitigators, and biopreservatives in ruminant production systems. Thus, they improve feed efficiency, nutrient utilization, and nitrogen retention while mitigating greenhouse gas emissions. In dairy systems specifically, phytogenic feedstuffs enhance milk yield and composition by enriching conjugated linoleic acids (CLAs), omega-3 fatty acids, and antioxidant compounds, leading to superior nutritional and oxidative stability. In meat production systems, they improve tenderness, flavor and shelf life through reduced oxidation and enhanced muscle metabolism. Despite these benefits, dose optimization, bio-efficacy, and species-specific responses remain critical research priorities. Use of phytogenic-based feeding strategies aligns with global sustainability goals by reducing reliance on feed additives, promoting environmentally resilient and circular food systems. This review synthesizes emerging evidence on the mechanisms, production outcomes, and functional benefits of dietary phytochemicals, providing a scientific framework for their strategic application in sustainable ruminant milk and meat production.