Ruderal Tithonia diversifolia inclusion in sheep diets: impacts on digestibility and greenhouse gas emissions

Emissions from ruminant livestock represent an important component of agricultural greenhouse gas output. The sector, however, has substantial potential for emission reduction through improved practices. Tithonia diversifolia (TD), a shrub that thrives in low-fertility soils, offers promise as a sustainable feed alternative. This study explores whether ruderal TD, accessible but with variable nutritional quality, can be used to reduce enteric methane (CH4) emissions and nitrogen (N) excretion in sheep, offering a low-input strategy for enhancing ruminant sustainability. Eight adult rams were used to evaluate diets with 4 increasing levels of TD hay on carbon dioxide (CO2), CH4, nitrous oxide (N2O) and ammonia (NH3) emissions, apparent digestibility, and fermentation parameters. The animals received four increasing levels of TD hay (0, 90, 270, 450 g kg-1 DM) in a diet based on Tifton 85 hay, soybean meal, and ground corn. Feeding sheep with ruderal TD had no effects on intake and N balance but reduced digestibility of dry matter, organic matter, neutral and acid detergent fiber, while crude protein digestibility remained unaffected. There was also a decrease in acetate and ruminal N-NH3 concentrations, alongside an increase in iso-acid proportions. CO2, CH4, N2O and NH3 emissions were consistent across diets, averaging 98.05 gCO2 kg-1 DMI, 9.3 gCH4 kg-1 DMI, 2.62 gN2O kg-1 excreted N, and 37.8 gNH3 kg-1 excreted N. In conclusion, incorporating ruderal TD into sheep diets reduced nutrient digestibility and ruminal fermentation but did not impact feed intake, protein digestibility, or greenhouse gas emissions.