2.2. Sample Collection and Chemical Analysis Program

All experiments consisted of a 5 d diet adaptation followed by a 5 d period of total collection of feces and urine. During the 5 d collection period, feces were collected into a plastic bag every 4 h from 0800 to 2200 h and then stored at −20 °C. At the end of the experiment, the 5 d of collected feces from each pig were pooled, mixed, and weighed; an 800 g subsample was taken and dried in a forced-draft oven at 65 °C for 72 h. After drying and grinding through a 1 mm screen, fecal subsamples were stored at −20 °C for further chemical analysis. Total urine was collected in plastic buckets attached to funnels located under the metabolism cages at the same time as the fecal collection. Approximately 50 mL of 6 N HCl was added to each bucket to limit microbial growth and reduce the loss of ammonia. Urine volume was recorded daily and a subsample of 10% was collected and stored at −20 °C. At the end of the collection period, urine samples were pooled within each pig and a subsample (about 100 mL) was stored at −20 °C for further analysis.

The chemical analysis of all samples was tested in duplicate. Samples were analyzed for dry matter (DM) (procedure 934.01), crude protein (CP) (procedure 990.03), ether extract (EE; procedure 920.39), and ash (procedure, 942.05) by Association of Official Analytical Chemists (AOAC) methods [10]. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were determined using fiber bags (Model F57, Ankom Technology, Macedon, NY, USA) and a fiber analyzer (ANKOM200 Fiber Analyzer, Ankom Technology, Macedon, NY, USA) after adaptation of the procedure described by Van Soest et al. [11]. The ADF fraction was analyzed in a separate sample. The gross energy (GE) of corn, SBM and WB, diets, feces, and urine samples were analyzed using an adiabatic oxygen bomb calorimeter (Parr Instruments Co., Moline, IL, USA). Soluble carbohydrates (SCHO) were calculated from analyzed nutrient values as 100 − (protein + fat + ash + NDF) [12,13].