The objective of this experiment was to develop a new computer-controlled simulated digestion system to predict the digestible energy (DE) and metabolizable energy (ME) of unconventional plant protein meals for growing pigs. Nine meals tested included 1 source of rapeseed meal, 4 sources of cottonseed meal, 2 sources of sunflower meal, and 2 sources of peanut meal. Twenty growing pigs (Duroc × [Landrace × Large White]) with an initial body weight (BW) of 41.7 ± 2.6 kg were allotted to a replicated 10 × 3 incomplete Latin square design to determine the DE and ME of 1 basal diet and 9 experimental diets formulated with 9 unconventional plant protein meals. The DE and ME values of unconventional plant protein meals were calculated by the difference method. The in vitro digestible energy (IVDE) of 1 basal diet, 9 experimental diets, and 9 unconventional plant protein meals were determined with 5 replicates of each sample in a complete randomized arrangement. The IVDE/DE or IVDE/ME ranged from 0.96 to 0.98 or 1.00 to 1.01, and the correlation coefficient between IVDE and DE or ME was 0.97 or 0.98 in 10 experimental diets. Accordingly, the IVDE/DE or IVDE/ME ranged from 0.86 to 1.05 or 0.96 to 1.20, and the correlation coefficient between IVDE and DE or ME was 0.92 or 0.91 in 9 unconventional plant protein meals. The coefficient of variation (CV) of IVDE was less than that of DE and ME in the experimental diets (0.43%, 0.80%, and 0.97% for CV of IVDE, DE and ME, respectively) and unconventional plant protein meals (0.92%, 4.84%, and 6.33% for CV of IVDE, DE and ME, respectively). The regression equations to predict DE from IVDE in 10 experimental diets and 9 unconventional plant protein meals were DE = 0.8851 × IVDE +539 (R² = 0.9411, residual standard deviation [RSD] = 23 kcal/kg DM, P < 0.01) and DE = 0.9880 × IVDE + 166 (R² = 0.8428, RSD = 182 kcal/kg DM, P < 0.01), respectively. There was no statistical difference in the slopes (P = 0.82) or intercepts (P = 1.00) of these 2 equations. Thus, 10 diets and 9 unconventional plant protein meals were pooled to establish the regression equation of DE on IVDE as: DE = 0.9813 × IVDE +187 (R² = 0.9120, RSD = 118 kcal/kg DM, P < 0.01). The regression equations to predict ME from IVDE in 10 experimental diets and 9 unconventional plant protein meals were ME = 0.9559 × IVDE +146 (R² = 0.9697, RSD = 18 kcal/kg DM, P < 0.01) and ME = 0.9388 × IVDE + 3 (R² = 0.8282, RSD = 182 kcal/kg DM, P < 0.01), respectively. There was no statistical difference in slopes (P = 0.97) but significant difference between the intercepts (P = 0.02) of these 2 equations. Our results indicate IVDE has similar response to the DE but different response to the ME in 10 experimental diets and 9 unconventional plant protein meals. Therefore, IVDE is more suitable to predict DE than ME of diets and unconventional plant protein meals for growing pigs.

Phytase activity can be impaired during pelleting because of extreme thermal conditions. This study investigated the effects of dose and source of phytase on phytase activity during the conditioning, pelleting, and cooling process. A split-plot design was used in two experiments, with five phytase doses (Exp. 1; 7560, 14310, 33830, 43590 and 61500 FTU/kg) or eight phytase sources (Exp. 2) as the main plot and steam conditioning temperatures (Exp. 1 and 2; 75 and 85 °C) as the subplot. Each treatment processed four batches, one batch per replicate. The results of Exp. 1 showed phytase dose in diets had no effect (p > 0.05) on the recovery rate of phytase activity after the conditioning, pelleting, or cooling process. The recovery rate of phytase activity in each process was higher (p < 0.05) at 75 °C than that at 85 °C for both Exp. 1 and 2. The phytase source significantly affected (p < 0.05) the recovery rate of phytase activity and had varied appearances of structure. In conclusion, the structure, phytase activity, and phytase recovery after steam conditioning–pelleting significantly varied across sources, but the stability of phytase was not affected by dose.

Two experiments were conducted to validate the sensitivity and accuracy of in vitro digestible energy (IVDE) determined with a computer-controlled simulated digestion system (CCSDS) to predict metabolizable energy (ME) of diets for roosters. In experiment 1, soybean hulls were added to a basal diet (calibration diet 1) at 2.06, 4.12, 6.17, 8.23, 10.28, 12.32, or 14.37% of the diets (calibration diets 2–8) to produce an interval of approximately 80 kcal ME/kg. The sensitivity was measured by comparing the determined and actual IVDE of the diets. With these data, a linear model was developed to predict ME from IVDE. In experiment 2, validation diets were identical except they were composed of different cereal ingredients. For each diet, the correlations and ratios between IVDE and ME were analyzed to test the sensitivity of IVDE to predict ME across different ingredients. In experiment 1, a slope of 0.9899 was calculated in a linear regression of determined IVDE on actual IVDE (R2 = 0.9998; P < 0.01). The ratio of determined IVDE to actual IVDE was 0.9878. The ratio of IVDE to apparent metabolizable energy (AME) and to nitrogen-corrected AME (AMEn) was 1.03 and 1.05, respectively. The linear models to predict ME from IVDE were AME = 0.8449 × IVDE + 451 (R2 = 0.9812, residual standard deviation [RSD] = 28 kcal/kg; P < 0.01) and AMEn = 0.8357 × IVDE + 436 (R2 = 0.9821, RSD = 27 kcal/kg; P < 0.01). In experiment 2, a significant simple correlation was observed between the IVDE and AME or AMEn of validation diets (r > 0.97; P < 0.01). The ratio of IVDE to AME and to AMEn was 1.04 and 1.05, respectively. Predicted and determined AME or AMEn of 8 validation diets differed by less than 100 kcal/kg. The regression of determined AME or AMEn against predicted AME or AMEn (R2 ≥ 0.9466; P < 0.01) resulted in an overlapped line where Y = X. These results suggest the IVDE determined with CCSDS is highly sensitive and can be used to accurately predict the ME of diets for roosters across a wide range of cereal grains.

This experiment evaluated the difference between computer-controlled simulated digestion and in vivo stomach-small intestinal or large intestinal digestion for growing pigs. Five diets including a corn-soybean meal basal diet and four experimental diets with rapeseed meal (RSM), cottonseed meal (CSM), sunflower meal (SFM), or peanut meal (PNM) were assigned to each group of five barrows installed terminal ileal cannula or distal cecal cannula in a 5×5 Latin square design. Ileal digesta and feces were collected for the determination of digestibility of dry matter (DM) and gross energy (GE) as well as digestible energy (DE) at terminal ileum and total tract. The large intestinal digestibility and DE were calculated by the difference between measurements obtained at the terminal ileum and those obtained from total tract. In vitro stomach-small intestinal digestibility and DE for diets and plant protein meals were determined by stomach-small intestinal digestion in a computer-controlled simulated digestion system (CCSDS). The in vitro large intestinal digestibility and DE of diets were determined in a CCSDS using ileal digesta and enzymes extracted from cecal digesta of pigs. The in vitro large intestinal digestibility and DE of four plant protein meals were determined by the difference between stomach-small intestinal and total tract digestion in the CCSDS. For the experimental diets, the in vitro ileal digestibility and DE were not different from corresponding in vivo values in basal diet and PNM diet, but greater than corresponding in vivo values for diets with RSM, CSM and SFM (P < 0.05). No difference was observed between in vitro and in vivo large intestinal digestibility and DE in five diets. For the feed ingredients, the in vitro ileal digestibility and DE did not differ from corresponding in vivo ileal values in RSM and PNM but were greater than the in vivo ileal values in CSM and SFM (P < 0.05). The in vitro large intestinal GE digestibility and DE were not different from in vivo large intestinal values in RSM, CSM, and PNM, but lower than in vivo large intestinal values in SFM. This finding may relate to the higher fiber content of plant protein meals resulting in shorter digestion time of in vivo stomach-small intestine thus lower digestibility compared to in vitro, indicating it is necessary to optimize in vitro stomach-small intestinal digestion time.

This study determined metabolizable energy (ME) and developed ME prediction equations for broilers based on chemical composition of soybean meal (SBM) and rapeseed meal (RSM) using a 2 × 10 factorial arrangement of age (11 to 14 or 25 to 28 d of age) and 10 sources of each ingredient. Each treatment contained 6 replicates of 8 broilers. The ME values were determined by total collection of feces and urine. Principal components analysis (PCA) of the chemical composition clearly revealed distinct differences in SBM and RSM based on a principal components (PC) score plot. The nitrogen-corrected apparent metabolizable energy (AMEn) of SBM was higher in broilers from 25 to 28 than 11 to 14 d of age (P = 0.013). Interactions between broiler age and ingredient source affected apparent metabolizable energy (AME) of SBM and ME of RSM (P < 0.05). The ME of SBM in 11 to 14 and 25 to 28-day-old broilers were estimated by crude protein (CP) content (R²≥ 0.782; SEP ≤ 83 kcal/kg DM; P < 0.001). The AME and AMEn of RSM in 11 to 14-day-old broilers were estimated by ether extract (EE), ash and acid detergent fiber (ADF) (R² = 0.897, SEP = 106 kcal/kg DM; P = 0.002), and by EE and ash (R² = 0.885, SEP = 98 kcal/kg DM; P = 0.001), respectively. The AME and AMEn of RSM in 25 to 28-day-old broilers were estimated by ash and ADF (R² = 0.925, SEP = 104 kcal/kg DM; P < 0.001) and by ash and neutral detergent fiber (NDF) (R² = 0.921, SEP = 91 kcal/kg DM; P < 0.001), respectively. These results indicate that ME of these 2 plant protein ingredients are affected interactively by chemical composition and age of broilers. This study developed robust, age-specific prediction equations of ME for broilers based on chemical composition for SBM and RSM. Overall, ME values can be predicted from CP content for SBM, or EE, ash, ADF, and NDF for RSM.

Two experiments were conducted to study the effect of dietary cottonseed meal (CM) and soybean oil (SO) on passage time of digesta and standardized ileal digestibility (SID) of amino acids (AA). The experimental design was a 2 × 2 factorial arrangement evaluating the levels of CM (20 or 40 %) and SO (0 or 10 %). Experiment 1 estimated the effect of CM and SO on the passage time of digesta. Twenty-five Chinese yellow-feathered roosters (BW = 2.61 ± 0.08 kg; 26-wk-old) were individually weighed and allocated to 5 diets in 5 randomized complete blocks by initial BW. Experimental diet 1 contained 20% CM and 0 SO, diet 2 contained 20% CM and 10% SO, diet 3 contained 40% CM and 0% SO, diet 4 contained 40% CM and 10% SO, and a nitrogen-free diet was also fed. Passage time through the total digestive tract was determined by time-relative cumulation of dry excreta. Experiment 2 estimated the effect of CM and SO on SID of AA in CM. Thirty Chinese yellow-feathered roosters (BW = 2.91 ± 0.05 kg; 26-wk-old) were allocated to the 5 experimental diets in 6 randomized complete blocks by initial BW to determine the SID of AA. Increasing CM concentration significantly reduced the time for 50% relative cumulation of dry excreta (P < 0.05). Adding 10% SO tended to increase the time for 50% relative cumulation of dry excreta (0.05 < P < 0.10) relative to diets without SO. Dietary CM and SO did not affect the SID of indispensable AA or dispensable AA of CM significantly, but increasing dietary CM tended to reduce the SID of Lys (0.05 < P < 0.10). Increasing SO tended to reduce the SID of Met (0.05 < P < 0.10). There were no significant interactive effects of SO and CM (P > 0.10). These results suggest passage time is increased with dietary SO, and reduced with dietary CM, but digestibility of AA in CM was not significantly affected by dietary CM and SO.