The objectives were to evaluate previous equations for estimating gross energy (GE) of pig urine using urinary nitrogen (N) and to develop novel equations for estimating GE concentrations of pig urine. A total of 136 urine samples were obtained from pigs fed 18 diets in 2 experiments. The samples were analyzed for GE and N concentrations. The accuracy of previous equations was assessed by regressing the measured values minus the predicted values for urinary GE concentration on the predicted values centered to the mean. Novel equations for estimating the urinary GE concentration were developed using urinary N concentration and body weight (BW) as independent variables. The previous equations overestimated (mean bias; p<0.001) urinary GE concentrations and the overestimation was more pronounced for the low-GE urine samples (linear bias; p<0.001). The novel equations developed in the present work were: urinary GE concentration (kcal/kg) = –7.51+12.83×urinary N (r2 = 0.92 and p<0.001) and –16.33+14.00×urinary N+0.192×BW–0.030×urinary N×BW (R2 = 0.92 and p<0.001) where N as g/kg and BW as kg. Overall, the previous equations overestimate urinary GE, particularly for low-GE urine of pigs. Gross energy concentrations in urine can be fairly accurately estimated using urinary N concentration and BW.

Objective: The present experiment aimed to determine standardized ileal digestibility (SID) of amino acids (AA) and digestible energy (DE) in four bakery byproducts fed to nursery piglets and to develop prediction equations for estimating SID of AA and DE in bakery byproducts.Methods: Five barrows with an initial body weight of 16.6 kg (standard deviation = 1.7) were fitted with a T-cannula at the distal ileum and individually housed in pens. A 5×5 Latin square design was used with 5 treatments, 5 pigs, and 5 periods. Four sources of bakery byproducts containing 9.1% to 38.4% neutral detergent fiber (NDF) were used. Three experimental diets contained each bakery byproduct at 96.6% as the sole source of nitrogen and energy. The fourth experimental diet consisted of a source of bakery byproduct (38.4% NDF) at 70.0% as the sole source of nitrogen. A nitrogen-free diet was prepared to determine the basal endogenous AA losses. Each period consisted of 6 d of adaptation, 1 d of fecal collection, and 3 d of ileal collection.Results: The SID of most AA and DE differed (p<0.05) among 4 bakery byproducts. The NDF concentration was negatively correlated (p<0.05) with the SID of indispensable AA except Lys and DE in bakery byproducts. Prediction equations were developed for estimating SID of AA and DE: SID of Met (%) = 86.7–0.54×NDF (r2 = 0.74 and p<0.001); SID of Thr (%) = 73.4–1.00×NDF (r2 = 0.57 and p<0.001); and DE (kcal/kg as-is) = 4,819– 81.96×NDF (r2 = 0.93 and p<0.001), where NDF is expressed as % as-is.Conclusion: Amino acid digestibility and DE variede among bakery byproducts fed to nursery piglets. Neutral detergent fiber can be used to estimate SID of AA and DE in bakery byproducts for nursery piglets.

Objective: The present study aimed to determine the effects of supplemental 3-phytase, 6-phytase, or both on total tract digestibility of phosphorus (P) and calcium in cornsoybean meal-based diets fed to growing pigs.Methods: Twelve barrows with an initial body weight of 63.1±3.0 kg were allotted to a triplicated 4×3 incomplete Latin square design with 4 diets and 3 periods to obtain 9 observations per diet. The experimental diets comprised 1) a control diet based on 73.3% corn and 23.0% soybean meal without inorganic P source or supplemental phytase, 2) the control diet supplemented with 1,000 phytase unit (FTU)/kg of 3-phytase, 3) the control diet supplemented with 1,000 FTU/kg of 6-phytase, and 4) the control diet supplemented with both 3-phytase at 500 FTU/kg and 6-phytase at 500 FTU/kg.Results: Supplemental phytase reduced (p<0.05) the daily P output from pigs regardless of the phytase source or the combination of the 2 phytase sources. The pigs fed the diet supplemented with 6-phytase or both 3-phytase and 6-phytase had less daily P output compared with those fed the diet supplemented with only 3-phytase (p<0.05). The total tract digestibility of P in pigs fed the diet supplemented with both 3-phytase and 6-phytase was greater (p<0.05) than those fed the control diet or the diet supplemented with only 3-phytase. The apparent total tract digestibility of calcium in pigs fed the diet supplemented with 6-phytase or both 3-phytase and 6-phytase was greater compared with the control group (p<0.05).Conclusion: Taken together, supplemental phytase increased P digestibility in cornsoybean meal-based diets fed to growing pigs regardless of the phytase sources and the effects of supplemental phytase on the P and calcium digestibility were most pronounced in the mixture of 3-phytase and 6-phytase.

The present study aimed to develop equations for estimating the dry matter (DM), nitrogen (N), and gross energy (GE) concentrations in pig urine using Brix values. A total of 96 urine samples were obtained from pigs of 6.0 to 62.2 kg initial body weight fed 12 diets in three experiments. The animals were fed a corn-soybean meal-based diet or a corn diet. The N concentrations in the urine samples ranged from 0.12% to 2.06% and the GE concentrations ranged from 2 to 187 kcal/kg. The urine Brix values were positively correlated with urinary DM, N, and GE concentrations (r = 0.94, 0.87, and 0.93, respectively; p<0.001). The models for estimating urinary DM, N, and GE concentrations were: urinary DM (%) = 0.590×Brix+0.315 (r2 = 0.91; p<0.001); urinary N (%) = 0.0798×Brix+0.148 (r2 = 0.84; p<0.001); urinary GE (kcal/kg) = 11.96×Brix+2.33 (r2 = 0.87; p<0.001), where the Brix value of urine is expressed as %. Overall, the Brix values correlated positively with the DM, N, and GE concentrations in pig urine and can thus be used for estimating the concentrations of these urinary components.

This study aimed to test the additivity of digestible phosphorus (P) in mixed diets fed to pigs and to investigate the effects of P expressions in diet formulations on P excretion from pigs. In experiment 1, eight castrated male pigs (30.5 ± 1.5 kg) were allotted to a replicated 4 × 4 Latin square design. Three experimental diets contained wheat, soybean meal, or both as the sole P source, and a P-free diet was prepared to determine the basal endogenous losses of P. In experiment 2, twenty-four castrated male pigs (18.1 ± 0.7 kg) were allotted to a completely randomized design. Three experimental diets were prepared based on the total, apparent total tract digestible (ATTD), or standardized total tract digestible (STTD) P. In experiment 1, the measured ATTD of P in the mixed diet was greater (p < 0.05) than the predicted values, but no difference was observed in the STTD of P in the mixed diet. In experiment 2, the daily P output of the pigs fed the diet based on ATTD P was greater (p < 0.05) than that based on the total or STTD P. Overall, the STTD P provides a more accurate and additive measure of biologically available P in mixed diets for pigs, and the use of STTD P in formulations may reduce P excretions.