Eucheuma cottonii-enriched legume-based green concentrate improves rumen protein utilization, methane mitigation, and...

Legume-based green concentrate (GC) is a promising, low-cost feeding strategy for dairy systems; however, its high rumen-degradable protein (RDP) fraction limits nitrogen utilization efficiency. This study evaluated the effect of Eucheuma cottonii enrichment as a rumen-protected agent on feed quality, rumen protein utilization, methane mitigation, and lactation performance in Holstein Friesian dairy cows.

The experiment comprised integrated in vitro and in vivo phases. In the in vitro phase, GC was enriched with E. cottonii at 0%, 2.5%, 5%, 7.5%, and 10% and assessed for digestibility, rumen protein utilization (RDP and rumen-undegradable protein [RUP]), gas production, and fermentation characteristics. In the in vivo phase, eighteen postpartum cows were randomly assigned to three dietary treatments: commercial concentrate, GC, and GC enriched with 10% E. cottonii for 60 days. Parameters included milk yield, dry matter intake, feed conversion efficiency (FCE), milk quality, and economic returns.

E. cottonii enrichment significantly improved feed quality and rumen protein utilization. A marked reduction in RDP and a concurrent increase in RUP were observed (p < 0.01), indicating enhanced protein bypass. Digestibility indices, including in vitro dry matter, organic matter, crude protein, and gross energy digestibility, were significantly increased (p ≤ 0.002). Methane production and total gas output were reduced (p ≤ 0.01), reflecting improved rumen fermentation efficiency. In the in vivo trial, cows fed 10% enriched GC exhibited higher milk yield (p = 0.01), improved FCE (p = 0.02), and enhanced milk fat and protein contents (p < 0.01). Economic analysis demonstrated reduced feed costs and increased daily profit. The functional mechanism is attributed to kappa-carrageenan in E. cottonii, which forms a protective matrix limiting microbial proteolysis.

Enrichment of GC with E. cottonii effectively optimizes rumen protein utilization, enhances digestibility, reduces methane emissions, and improves lactation performance and farm profitability. This strategy represents a sustainable, cost-effective innovation for improving dairy productivity and environmental efficiency.