Methane digester effluent from swine excreta as a nutrient and water source for growing and finishing swine

The experimental objective was to evaluate swine methane digester effluent (SMDE) as a water and nutrient source for swine. The mesophilic methane digester was loaded daily with manure from finishing swine fed a corn-soybean meal diet. Dry diet was mixed with SMDE (3.7% DM) and fed twice daily in troughs. Tap water was provided and consumption measured. Barrows were group fed (3 pigs/pen) and adapted to SMDE by increasing SMDE for 7 d, with the full amount fed from d 8 to the end of the feeding phase (d 21, 14, 23, or 37 for Exp. 1 to 4, respectively). Blood samples were collected on d 0, 10, 21, and 31 to determine plasma concentrations of glucose and plasma urea N (PUN). Barrows were placed in individual metabolism cages for a 5-d acclimation and a 5-d fecal and urine collection to determine apparent N and energy utilization. For Exp. 1, 18 pigs averaging 75 kg BW were allotted to diets with 0, 48.6, or 63.7% SMDE, as-fed basis. For Exp. 2 and 3, 12 pigs/experiment averaged 117 and 70 kg, respectively, and were allotted to diets with 0 or 63.7% SMDE, as-fed basis. At the end of Exp. 2 and 3, pigs were sacrificed and liver samples were collected to determine urea cycle enzyme activity, and loin was saved for taste panel evaluation. For Exp. 4, pigs averaged 40 kg and were allotted to diets with 0 or 57.5% SMDE, as-fed basis. The ADFI, ADG, and G:F of finishing swine (Exp. 1 to 3) were not reduced by feeding diets containing 63.7% SMDE (as-fed basis), whereas ADG and G:F of growing swine (Exp. 4) were reduced (P < 0.01) by feeding a diet containing 57.5% SMDE. Pigs fed diets containing SMDE consumed 31 to 56% less (P < 0.05) water and had greater (P < 0.01) PUN concentrations than pigs fed control diets. Pigs fed diets containing SMDE excreted more (g, P < 0.05) fecal N and absorbed and retained less N (%; P < 0.01) and energy (DE and ME) than pigs fed control diets. Treatment had no effect on urea cycle enzyme activity. In conclusion, finishing swine adapted to diets containing 63.7% SMDE (as-fed basis) based on growth performance, whereas growing swine did not adapt to a diet containing 57.5% SMDE because of the large content of nonprotein N in SMDE. Recycling SMDE to swine greatly reduced fresh water consumption, whereas the protein and energy values of SMDE were approximately 0 for swine. Therefore, SMDE is more appropriately recycled as a source of water and N for ruminant nutrition or crop production.