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

SIMPLE SUMMARY: The economics of livestock production depends upon the feasible feeding resources as feed costs constitute more than 70% of the total expenses of a livestock enterprise. In this regard, searching for alternative and cheaper feeding resources is imperative for economical and sustainable livestock production. Mulberry leaves are an important resource available for feeding livestock, as they possess quite high protein and energy contents as compared to other tree leaves and conventional forages. Moreover, polyphenolic compounds (mainly flavonoids) present in mulberry leaf (ML) possess excellent antioxidant and antimicrobial potential that can beneficially impact animal health and production. Mulberry leaves and its flavonoids have been shown to increase the feed digestibility and milk production in ruminants, while reducing methane emission. Moreover, mulberry flavonoids can positively influence body metabolism and alleviate oxidative stress in animals. This review highlights the importance of this unique feeding resource for ruminants to increase their performance while reducing methane emissions. ABSTRACT: Leaf biomass from the mulberry plant (genus Morus and family Moraceae) 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 (CH(4)) 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 CH(4) emission.