Influência da inclusão de monensina na dieta de ovelhas sobre a composição dos dejetos e potenciais de geração de biogás e metano

Abstract

Monensin is widely used in ruminant feed, but a portion of this ionophore is excreted in feces, potentially disrupting waste treatment processes such as anaerobic digestion by reducing methane (CH4) production. Physical separation of solid-liquid fractions may reduce the fibrous content and monensin concentration in substrates. This research aimed to evaluate the impact of monensin doses in sheep feed on the anaerobic digestion of waste at two hydraulic retention times (HRT). We used waste from Pantaneira sheep fed with 0, 8, 14, and 20 mg of monensin per kg of dry matter. Waste was collected, scraped from stalls, prepared, and sieved (1 mm mesh) to separate the fractions, resulting in non-sieved (NP) and sieved (P) substrates. Digestion times of 20 and 30 days (HRT 20 and 30) were independently evaluated. An initial total solids (TS) concentration of 3% was used, with lower values in sieved substrates. Monensin negatively impacted all evaluated parameters, with effects intensifying at higher doses. TS reduction averaged 48.05% for the control group and 35.06% for the 20 mg group (HRT 30, NP condition), with volatile solids (VS) showing similar trends. Biogas production was highest in the control group, with 173,03 and 239,0 l/kg TS added in both HRTs (20 and 30 days) in the P condition, and decreased with higher monensin inclusion. Maximum methane production was achieved at 0 mg monensin in both HRT and substrate conditions (P and NP), while the lowest was at 20 mg. Neutral detergent fiber (NDF) content increased with higher monensin doses, averaging 54.73% and 56.26% for 0 and 20 mg respectively in the NP condition. Chemical oxygen demand (COD) values were lower with higher monensin presence and longer HRT. These results demonstrate a detrimental effect of monensin on biogas and CH4 production potentials under both conditions (NP and P) and HRTs (20 and 30 days). Fraction separation and a 30-day HRT are crucial for optimizing biogas and methane production during anaerobic digestion, enhancing substrate-to-energy conversion efficiency.