Influência da monensina na dieta de bovinos sobre as características dos dejetos e alternativas de minimizar os impactos no tratamento dos resíduos

Abstract

Chapter 1 - This chapter aims to review the literature on the use of monensin in animal feed and the use of techniques for the degradation of this ionophore before using animal waste as an organic fertilizer. This ionophore is widely used as a rumen modulator in cattle farming due to its action in reducing methanogenesis and energy losses. However, there is still monensin in waste and this can harm waste treatments with anaerobic digestion and composting, such as reducing biogas production or reducing degradation of organic material. With the solid-liquid fraction separation technique, it is possible to reduce amounts of antibiotics in both the solid and liquid fractions, which can be favorable for mitigating losses, in addition to the smaller amount of fibrous material, which can result in greater efficiency in waste treatments. Chapter 2 – Objective: To carry out the characterization and anaerobic digestion of cattle waste fed with monensin inclusions, with separation of the fractions in two hydraulic retention times (HRT). A reduction in ST masses was observed in the waste produced with the increase in monensin levels, with 4.76 kg (control), reaching 4.05 kg (7.2 mg). The masses of SV and FDN also followed the behavior of ST. However, the opposite behavior occurred in the lignin masses, as their levels increased, starting from 4.68% (control), and in the highest dose of monensin, it was 11.36%. The dry matter ingested was not influenced by monensin with an average of 10.713 kg day-1. In anaerobic digestion, separation influenced the reductions of ST, SV, and NDF, achieving greater reductions and increasing the potential to produce biogas, methane, and their concentration, about those without separation. However, with the increase in monensin levels, there was a decrease in the parameters evaluated, in the two HRTs adopted. TRH20 was less efficient compared to TRH30 in solid degradation and biogas production. Therefore, it is recommended for the anaerobic digestion of bovine manure containing monensin to adopt HRT for 30 days, with sieving of substrates for better process efficiency. Chapter 3 – Objective: to compost waste from cattle fed with increasing doses of monensin and separate solid-liquid fractions. The temperature remained in the thermophilic phase for four consecutive weeks, and between the 5th and 9th week, it remained close to the thermophilic range, equaling the ambient temperature in the last weeks of composting, indicating the completion of the process. Most of the parameters evaluated (total and volatile solids, NDF, ADF, C) were initially influenced by monensin (p<0.05), with a tendency for smaller reductions in the initial period. However, with the advancement of composting, it was possible to obtain high reductions even at the maximum dose of monensin used. This behavior occurred regardless of sieving. The initial N reductions were not influenced (p>0.05) by monensin, whereas for total reductions the values obtained were similar with 37.2 and 38.51%, for NP and P, respectively. NPK concentrations (g/kg) were not influenced (p>0.05) by monensin doses in both sievings, with averages of 29.3, 12.9, and 1.2 for non-sieving, and 26.7, 10.4, and 0.9 for sieved, as well as the peaks of the functional groups. It is concluded that the concentrations of monensin used did not influence the quality of the final compound nor was there any influence of sieving on most of the parameters evaluated. Therefore, the waste can be used completely for composting.