Abstract

Seaweeds broadly classified as brown, red, and green algae, are rich in proteins, essential amino acids, polyunsaturated fatty acids, vitamins, and minerals, along with bioactive polysaccharides such as laminarin, fucoidan, carrageenan, and ulvan. These compounds exert diverse biological effects, including antioxidant, anti-inflammatory, prebiotic, and immunomodulatory functions, thereby improving gut health, feed efficiency, and overall productivity of ruminants. of particular importance is their ability to mitigate enteric methane emissions. Certain red seaweeds, such as Asparagopsis species, contain halogenated compounds like bromoform, which inhibit methyl-coenzyme M reductase, the key enzyme in methanogenesis, leading to significant reductions in methane output while redirecting hydrogen toward propionate formation, an energetically favorable pathway. This dual role of enhancing nutrient utilization and reducing environmental burden underscores their significance. Despite these advantages, challenges remain, including variability in nutrient composition across species and seasons, presence of recalcitrant polysaccharides that hinder digestibility, risks of heavy metal accumulation, excessive iodine levels, and nutrient instability during processing. Addressing these constraints through standardized harvesting, processing, and supplementation strategies will be critical for large-scale adoption. Overall, macroalgae hold great promise as a renewable, nutrient-dense, and ecofriendly feed additive and their inclusion in ruminant diets can improve animal health and productivity, reduce reliance on conventional feed resources, and contribute to global efforts in climate change mitigation and sustainable livestock production.

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