PSXIV-20 In vivo evaluation of enteric methane production in sheep fed diets composed of agro-industrial by-products.

Abstract Reducing greenhouse gas (GHG) emissions in livestock production is one of the major challenges in tropical animal agriculture. This study evaluated the use of Tithonia diversifolia (TD), a high-nutritional-value forage species with low agronomic requirements, combined with agro-industrial by-products, as a strategy to formulate sustainable diets for sheep. The objective was to investigate the effects of these diets on a sustainable production and enteric methane (CH₄) emissions. Four experimental diets were tested: three containing different combinations of agro-industrial by-products and one control diet composed of conventional ingredients (ground corn and soybean meal). The in vivo experiment was conducted with four Santa Inês rams in a 4×4 Latin square design, with four periods of 21 days each (14 days of diet adaptation and 7 days of data collection). Animals were housed in metabolism cages adapted for gas collection, enabling the evaluation of nutrient digestibility and GHG emissions. Preliminary results showed significant variations in methane emissions among the diets. Diet D2, consisting of TD, Tifton hay, ground corn, soybean meal, cassava bagasse, and sunflower meal, resulted in the highest CH₄ emission (22.87 L/d; 0.932 L/kg⁰·⁷⁵). In contrast, the control diet D0, with no by-products, presented the lowest emission (14.84 L/d; 0.618 L/kg⁰·⁷⁵). Diet D3, which included brewer’s yeast, showed promising results with moderate CH₄ emissions (16.77 L/d; 0.686 L/kg⁰·⁷⁵), suggesting effective fermentation of nutrients without compromising animal performance. These findings suggest that diets formulated with TD and agro-industrial by-products may improve the environmental sustainability of sheep production systems, contributing to the reduction of the carbon footprint.