Potential of Mulberry Leaf Biomass and Its Flavonoids to Improve Production and Health in Ruminants: Mechanistic Insights and Prospects

Leaf biomass from the mulberry plant (genus <i>Morus</i> and family <i>Moraceae</i>) is considered a potential resource for livestock feeding. Mulberry leaves (MLs) contain high protein (14.0-34.2%) and metabolizable energy (1130-2240 kcal/kg) with high dry matter (DM) digestibility (75-85%) and palatability. Flavonoid contents of MLs confer unique antioxidant properties and can potentially help alleviate oxidative stress in animals during stressful periods, such as neonatal, weaning, and periparturient periods. In addition, mulberry leaf flavonoids (MLFs) possess antimicrobial properties and can effectively decrease the population of ruminal methanogens and protozoa to reduce enteric methane (CH₄) production. Owing to its rich flavonoid content, feeding MLs increases fiber digestion and utilization leading to enhanced milk production in ruminants. Dietary supplementation with MLFs alters ruminal fermentation kinetics by increasing total volatile fatty acids, propionate, and ammonia concentrations. Furthermore, they can substantially increase the population of specific cellulolytic bacteria in the rumen. Owing to their structural homology with steroid hormones, the MLFs can potentially modulate different metabolic pathways particularly those linked with energy homeostasis. This review aims to highlight the potential of ML and its flavonoids to modulate the ruminal microbiome, fermentation, and metabolic status to enhance productive performance and health in ruminants while reducing CH₄ emission.