PSXI-3 Mineral changes of stacked, composted and vermicomposted manure from finishing pigs fed diets low in energy, calcium, phosphorus and trace minerals and added with exogenous enzymes

Abstract The objective of the study was to evaluate the changes in the concentration of macro- and micro-minerals of manure left in a manure stack or subjected to composting or vermicomposting excreted by finishing pigs fed diets reduced in metabolizable energy (ME), Ca, P and trace minerals and added with the exogenous enzymes phytase, xylanase and pectinase. Pigs were distributed into 3 treatments: 1) A Sorghum/soybean meal diet formulated to meet all the nutrient requirements, with a mineral premix based on sulfates; 2) Same as 1) but reduced in ME, Ca and P, and with reduction of 33.3% of the mineral premix, added with phytase, xylanase and pectinase; or 3) Same as 2), but with reduction of 66.6% of the mineral premix. The manure was collected every day from the pens and taken to a greenhouse with natural ventilation. One part of the manure was left in stacks, and the other part was subjected to precomposting for 28 d. After that, the precomposted manure was split in two; one part was left on the same trough and the second one was separated and inoculated with Red Californian worms. The composted and vermicomposted manure underwent a humification process for 90 d. At the beginning (fresh and precomposted manure) and end (stacked, composted and vermicomposted manure) of the study, samples were taken for analysis. The dry mater, ashes, total nitrogen, Ca, P, K, Na, Mg, Fe, Zn, Mn and Cu were determined. Results are expressed on a dry matter (DM) basis. There were three replications of manure piles, compost and vermicompost per treatment. Data were analyzed for a completely randomized design using the GLM procedures of SAS. In fresh manure, reduced Zn (1 = 334, 2 = 342 and 3 = 250 mg; P < 0.0456) and Mn (1 = 138, 2 = 135 and 3 = 119 mg; P < 0.050) were found in the manure originated from pigs fed diet 3) with a reduction of 66.6% of the mineral premix. At the end of the study, reduced P (1 = 1.21, 2 = 1.07 and 3 = 1.08%; P < 0.012), Zn (1 = 1103, 2 = 997 and 3 = 865 mg; P < 0.047), Mn (1 = 193, 2 = 167 and 3 = 146 mg; P < 0.019) and Cu (1 = 71, 2 = 53 and 3 = 45 mg; P < 0.003) were observed in the stacked manure originated from pigs fed diet 3). Reduced P (1 = 1.13, 2 = 1.07 and 3 = 0.95%; P < 0.014), Mn (1 = 235, 2 = 201 and 3 = 196 mg; P < 0.017) and Cu (1 = 47, 2 = 40 and 3 = 35 mg; P < 0.006) were found in the composted manure from pigs fed diet 3). In conclusion, in fresh manure from pigs fed reduced ME, Ca, P and mineral premix only Zn and Mn were reduced, whereas reduced P, Zn, Mn and Cu in stacked manure and reduced P, Mn and Cu in composted manure were found.