Optimizing Cichorium intybus var. Chico cutting age for biomass production, greenhouse gas emissions flux, and improved performance of thin-tailed sheep

<title>Abstract</title> <p> Forage harvest management shapes productivity and the environmental cost of ruminant systems, yet emissions from growing the forage are seldom measured alongside its feeding value. This study examined how the cutting age of <italic>Cichorium intybus</italic> var. Chico ( <italic>Cichorium intybus</italic> var. Chico) governs biomass yield, greenhouse gas (GHG) emissions, and downstream performance of thin-tailed sheep. A field experiment compared two cutting ages (40 and 60 days after regrowth) for biomass and in situ CO₂, CH₄, and N₂O fluxes measured by a static closed chamber. A separate feeding trial offered 20 thin-tailed sheep four diets in which <italic>C. intybus</italic> var. Chico replaced concentrate at 15, 25, 35, and 45% of dry matter (G1 to G4), recording intake, nutrient digestibility, and growth. Cutting at 40 days nearly doubled CO₂ flux (164.22 vs 84.52 mg/m²/day; P &lt; 0.01), whereas N₂O and CH₄ fluxes, fresh biomass (4.39 vs 4.91 ton/ha), and all yield-scaled emission intensities did not differ between ages. In sheep, higher <italic>C. intybus</italic> var. Chico inclusion kept dry matter intake stable while increasing crude protein intake (P &lt; 0.001). Dry matter digestibility, organic matter, crude fiber, and crude protein increase with <italic>C. intybus</italic> var. Chico level, peaking at 35–45% inclusion. Average daily gain increased from 94.57 g (G1) to 129.76 g (G4), and feed conversion ratio improved from 6.37 to 4.58 (P &lt; 0.001). Harvesting at 40 days delivers comparable biomass and emission intensity, and <italic>C. intybus</italic> var. Chico can replace up to 45% of concentrate while improving sheep performance, supporting sustainable tropical sheep production. </p>