The objectives were to demonstrate that nitrogen volatilization from pig urine can be inhibited by the addition of acids and to determine a minimum amount of HCl for nitrogen preservation in pig urine. In experiment 1, five urine samples were collected and had nitrogen concentrations of 0.29% to 0.68%. Each sample was divided into 2 groups that were supplemented with 100 mL of distilled water and 100 mL of 6 N HCl, respectively. The samples were placed in open containers at room temperature for 10 d. The nitrogen concentration was determined every 2 d. The amount of nitrogen in urine supplemented with distilled water decreased linearly (P < 0.001) with time, whereas that supplemented with 6 N HCl remained constant. In experiment 2, three urine samples with different nitrogen concentration (0.12%, 0.53%, and 0.94%) were added with different amounts of 6 N HCl used to make varying acidity (pH = 0.6, 1.1, 2.2, 4.7, 7.1, and 9.3). All urine samples were placed at a room temperature for 5 d followed by nitrogen analysis. Based on a linear broken-line analysis, nitrogen was not volatilized at a pH less than 5.12 (SE = 0.71), whereas nitrogen was volatilized at a pH greater than 5.12 (r2 = 0.98). An equation was developed for the minimum amount of 6 N HCl in urine to avoid nitrogen volatilization: 6 N HCl in urine (g/L) = 0.11 × nitrogen in urine (g/L) + 0.2 with r2 = 0.93 and P < 0.01. Assuming that up to 200 gram of nitrogen is excreted for 5 d, the addition of 100 mL of 6 N HCl to the urine collection container can inhibit nitrogen volatilization. Taken together, a minimum of 100 mL of 6 N HCl is recommended for 5 day-total collection of pig urine.

The objectives were to evaluate the nutrient utilization of fish meal, black soldier fly (BSF, Hermetia illucens) larvae, and adult BSF meal and to develop equations for estimating in vitro nutrient disappearance of BSF larvae for pigs. Two-step and 3-step in vitro procedures were used to simulate the digestion and absorption of nutrients in the gastrointestinal tract of pigs. In Exp. 1, defatted BSF larva meal had less (P < 0.05) in vitro ileal disappearance (IVID) of dry matter (DM; 81.2% vs. 91.6% and 61.6%) and crude protein (CP; 81.8% vs. 92.2% and 67.2%) and in vitro total tract disappearance (IVTTD) of DM (82.6% vs. 93.6% and 65.7%) and organic matter (OM; 78.1% vs. 91.5% and 63.2%) than fish meal and greater (P < 0.05) values than adult BSF. In Exp. 2, CP concentrations in BSF larvae were negatively correlated with ether extract (r = −0.91) but positively correlated with acid detergent fiber (ADF; r = 0.98) and chitin (r = 0.95). Acid detergent fiber and chitin concentrations in BSF larvae were negatively correlated with IVID of DM (r = −0.98 and −0.88) and CP (r = −0.87 and −0.84) and IVTTD of DM (r = −1.00 and −0.94) and OM (r = −0.99 and −0.98). Equations for in vitro nutrient disappearance of BSF larvae using ADF (% DM) as an independent variable were developed: IVID of CP, % = −0.95×ADF + 95 (r2 = 0.75 and P = 0.058) and IVTTD of OM, % = −2.60×ADF + 115 (r2 = 0.98 and P < 0.01). In conclusion, in vitro nutrient utilization of defatted BSF larva meal was less compared with fish meal but was greater compared with adult flies and in vitro nutrient utilization of BSF larvae can be predicted using ADF as an independent variable.

The objective of the present study was to determine standardized total tract digestibility of phosphorus (P) in black soldier fly (BSF; Hermetia illucens) larvae fed to pigs. Test ingredients were fish meal (66.2% crude protein, 9.2% ether extract, and 2.63% P), 3 sources of defatted BSF larva meal (43.1 to 59.2% crude protein, 8.6 to 13.2% ether extract, and 0.91 to 1.06% P), and a source of full-fat BSF larva (34.2% crude protein, 36.0% ether extract, and 0.70% P). Six barrows with an initial mean body weight of 78.1 kg (SD = 1.0) were individually housed in metabolism crates. Six diets were assigned to the 6 pigs in a 6 × 7 Latin square design with 7 periods resulting in 7 replicates for each treatment. Five experimental diets contained fish meal, defatted BSF larva meal, or full-fat BSF larva at 25% as the sole source of P. Additionally, a P-free diet mainly based on corn starch, sucrose, and gelatin was also prepared to estimate the basal endogenous losses of P. After a 4-day adaptation period, feces were collected for 4 days according to the marker-to-marker procedure. Apparent total tract digestibility of P in full-fat BSF larva (61.9%) was greater (P < 0.05) than that in 2 sources of defatted BSF larva meal (34.8% and 31.5%). Standardized total tract digestibility of P in full-fat BSF larva (71.8%) was greater (P < 0.05) than that in fish meal (51.0%) or 2 sources of defatted BSF larva meal (41.0% and 38.9%). The basal endogenous losses of P were estimated to be 189 ± 62 mg per kg dry matter intake. In conclusion, P in defatted BSF larva meal was less digestible compared with full-fat BSF larva.

The objective was to investigate the hindgut disappearance of phosphorus (P) in corn-soybean meal-based diets with or without inorganic P sources in pigs. Hindgut disappearance of P was hypothesized to be greater in a diet without inorganic P than in a diet with inorganic P. Barrows (n = 5; initial body weight = 23.5 ± 3.1 kg and final body weight = 33.7 ± 5.5 kg) fitted with a T-cannula in the distal ileum were individually housed in pens equipped with a feeder and a nipple drinker. Two corn-soybean meal-based diets were formulated with or without the inclusion of inorganic P. No phytase was supplemented to the diets. All diets contained 0.5% chromic oxide as an indigestible index. The pigs were allotted to a 2-period crossover design with 2 diets. A diet was fed to 2 pigs and the other diet was fed to 3 pigs in each period. An additional period was conducted after the 2 periods to obtain 2 additional replicates for each treatment. Each period consisted of a 7-d adaptation period, a 2-d fecal collection period, and a 2-d ileal collection period. Apparent ileal (54.7 vs. 35.0%) and total tract (53.7 vs. 34.3%) P digestibility values in the inorganic P-containing diet were greater (P < 0.01) than those in the diet without inorganic P. However, apparent ileal P digestibility values were comparable (P > 0.90) with apparent total tract P digestibility values irrespective of the inclusion of inorganic P in the diets, and thus, a significant amount of hindgut disappearance of P was not observed in both diets. In conclusion, hindgut disappearance of P in a corn-soybean meal-based diet was negligible in 23-kg growing pigs regardless of the inclusion of inorganic P sources.

The objective of the present study was to develop prediction equations for digestible energy (DE) and metabolizable energy (ME) in swine diets based on chemical compositions of feces with no dietary information. A total of 262 fecal samples obtained from growing pigs fed 27 diets from 4 experiments were used. The diets were based mainly on corn, soybean meal, and other plant-originated feed ingredients. In the digestibility experiments, feces and urine were quantitatively collected using the marker-to-marker procedure. The diet and fecal samples were analyzed for dry matter (DM), crude protein, ash, and neutral detergent fiber (NDF). Digestible energy in the 27 diets ranged from 2,907 to 4,374 kcal/kg DM and ME ranged from 2,774 to 3,983 kcal/kg DM. Fecal ash was positively correlated with DE (r = 0.81, P < 0.001) and ME (r = 0.66, P < 0.001) whereas fecal NDF was negatively correlated with DE (r = –0.66, P < 0.001) and ME (r = –0.74, P < 0.001). The energy prediction equations developed using fecal chemical components were: energy digestibility = 88.1 + 0.37 × ash – 0.28 × NDF (R2 = 0.57, P < 0.001); DE (kcal/kg DM) = 3,604 + 32.8 × ash – 11.1 × NDF (R2 = 0.71, P < 0.001); and ME (kcal/kg DM) = 4,077 + 15.7 × ash – 18.1 × NDF (R2 = 0.63, P < 0.001) where chemical components are expressed as % DM. In conclusion, energy digestibility, DE values, and ME values in swine diets are correlated with fecal ash and NDF concentrations and the energy values can be predicted using fecal ash and NDF concentrations without dietary information.