ABSTRACT

Background and Aim: 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. 

Materials and Methods: 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. 

Results: 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. 

Conclusion: 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. 

Keywords: dairy nutrition, Eucheuma cottonii, feed efficiency, green concentrate, methane mitigation, milk yield, rumen-protected protein, sustainability.