C. Pedersen

Amino acid digestibility of distillers dried grains with solubles, produced from sorghum, a sorghum-corn blend, and corn fed to growing pigs.

The objective of this experiment was to measure the concentration and digestibility of CP and AA in distillers dried grains with solubles (DDGS) produced from sorghum (S-DDGS) or a blend of sorghum and corn grains (SC-DDGS), and to compare these values with the digestibility of CP and AA in corn-based DDGS (C-DDGS). Eleven growing barrows (initial BW = 44.6 +/- 6.5 kg) were surgically fitted with a T-cannula in the distal ileum and allotted to a Youden square design with 11 diets and 8 periods. One diet contained 66.7% S-DDGS, 1 diet contained 66.7% SC-DDGS, 8 diets contained 66.7% C-DDGS, and 1 diet was N-free. Chromic oxide (0.3%) was used in all diets as an indigestible marker. The direct procedure was used to measure apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of CP and AA in the 10 sources of DDGS. Results of the experiment showed that the AID of Lys was not different among S-DDGS, SC-DDGS, and C-DDGS. The mean SID of CP, Arg, and Lys in C-DDGS were not different from values obtained in S-DDGS and SC-DDGS. The SID of Trp in S-DDGS (72.0%) was greater (P < 0.01) than in C-DDGS (64.9%), but there was no difference between C-DDGS and SC-DDGS (62.4%). The SID of CP and all AA were different among the 8 sources of C-DDGS (P < 0.01). Among the indispensable AA, Lys had the greatest variation and the SID ranged from 55.7 to 68.7%. The concentration of total and digestible AA was highly correlated (r(2)) for Arg (0.88), Ile (0.85), Leu (0.82), Phe (0.84), and Trp (0.84), but reduced r(2) values were observed for Lys (0.66) and Thr (0.39). A low correlation between the concentration and digestibility of AA indicates that it is desirable to develop in vitro procedures to predict digestible AA concentration in DDGS. In conclusion, SID values for CP and Lys in S-DDGS and SC-DDGS are within the range of values obtained in C-DDGS, but for many other AA, SID values in S-DDGS and in SC-DDGS are less than in C-DDGS.

Factors affecting the variability in ileal amino acid digestibility in corn distillers dried grains with solubles fed to growing pigs.

Two experiments were conducted to compare the ileal digestibility of AA in distillers dried grains with solubles (DDGS) sourced from different regions (IL, MN, KY), to compare AA digestibility in DDGS and in distillers dried grains (DDG) and to compare AA digestibility in DDGS from ethanol production (DDGS(ethanol)) and DDGS from beverage production (DDGS(beverage)). In Exp. 1, five samples of DDGS(ethanol) were sourced from Minnesota (MN1, MN2), Illinois (IL1, IL2), and from Kentucky (KY). In Exp. 2, six samples of DDGS(ethanol), 1 sample of DDG, and 1 sample of DDGS(beverage) were used to compare values for apparent ileal digestibility and standardized ileal digestibility (SID) of AA between DDGS(ethanol) and DDGS(beverage) and between DDG and DDGS(ethanol). Results of Exp. 1 showed that the SID of Lys in DDGS from MN2 (72.8%) was greater (P < 0.01) than in DDGS from MN1 (66.8%), IL1 (66.8%), and KY (65.8%) but not different from IL2 (70.1%). Except for Leu and Glu, no differences in SID for any of the other AA were observed among the 5 sources of DDGS. In Exp. 2, the SID for Lys in DDGS(beverage) was greater (P < 0.01) than in DDGS(ethanol) (69.3 vs. 64.8%), but for CP and all other AA except His, no differences between the 2 types of DDGS were observed. The SID for most AA in DDG were greater (P < 0.05) than in DDGS(ethanol), which suggests that the AA in the solubles that are added to DDGS may be less digestible than the AA in DDG. In conclusion, results of these experiments confirm that the digestibility of Lys is more variable among sources of DDGS than the digestibility of other AA. However, the SID of AA among DDGS sources within a region can vary as much as among DDGS sources from different regions, and AA in DDGS(beverage) may be as digestible as AA in DDGS(ethanol). The digestibility of AA in DDG is greater than in DDGS, which indicates that AA in the solubles have a lower digestibility than AA in DDG.

Application of the Reactive Lysine Procedure To Estimate Lysine Digestibility in Distillers Dried Grains with Solubles Fed to Growing Pigs

Two experiments were conducted to measure the reactive Lys concentration in corn distillers dried grains with solubles (DDGS). In expt 1, reactive Lys was measured in 33 sources of DDGS using two procedures: the homoarginine procedure and the furosine procedure. The concentration of reactive Lys in DDGS was then correlated with the concentration of standardized ileal digestible (SID) Lys in DDGS fed to growing pigs. In expt 2, a factorial experiment was conducted using four ratios of condensed distillers solubles (CDS) and wet distillers grain (WDG). The ratios (wt/wt) of CDS to WDG were 0:100, 20:80, 40:60, and 100:0, and four subsamples from each combination were freeze-dried or oven-dried at 50, 75, or 100 degrees C. The dried samples were designated DDG, DDGS 20, DDGS 40, and CDS, respectively. All subsamples were analyzed for total Lys and for reactive Lys using the homoarginine procedure. Results of expt 1 showed that only 74.1% of total Lys was reactive if measured by the homoarginine procedure and 83.5% was reactive if measured by the furosine procedure. The concentration of SID Lys in DDGS was correlated with the concentration of reactive Lys measured by the homoarginine procedure ( r (2) = 0.70, P < 0.05) and by the furosine procedure ( r (2) = 0.66, P < 0.05). In expt 2, the concentrations of total Lys and reactive Lys were reduced ( P < 0.05) when addition of CDS or drying temperature of the samples was increased, but the reduction was greater ( P < 0.05) when both CDS addition and drying temperature were increased at the same time. After oven-drying at 100 degrees C, 75.7% of total Lys was reactive in DDG, but only 27.6 and 10.2% were reactive in DDGS 20 and DDGS 40, respectively. In conclusion, reactive Lys is correlated with the concentration of SID Lys in DDGS, and addition of CDS exacerbates the negative effects of heating on the concentration of total Lys and reactive Lys in DDGS.

Apparent and true total tract digestibility of phosphorus in field peas (Pisum sativum L.) by growing pigs

The apparent (ATTD) and true (TTTD) total tract digestibility of P in field peas were measured using growing pigs. Two diets based on field peas without or with microbial phytase were formulated. A P-free diet was also formulated to measure endogenous losses of P. Results of the experiment showed that the ATTD and TTTD of P in field peas with microbial phytase (65.9 and 72.3%, respectively) were greater (P < 0.01) than in field peas without microbial phytase (55.0 and 60.8%, respectively). The addition of microbial phytase to field peas also reduced (P < 0.01) the excretion of P in the feces (from 5.77 to 4.09 g/5 d). Key words: Digestibility, endogenous losses, field peas, phosphorus, pig

Standardized ileal digestibility of reactive lysine in distillers dried grains with solubles fed to growing pigs.

The Maillard reaction can occur during the production of distillers dried grains with solubles (DDGS) as a result of the addition of condensed solubles to the wet distillers cake during drying. The Maillard reaction can lead to the formation of unavailable or unreactive lysine as a result of binding of reducing sugars to the epsilon-NH(2) group of Lys. The Lys that remains unbound is called reactive Lys. The conventional procedure to measure the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of total Lys in DDGS may overestimate the amount of digestible Lys in DDGS because this procedure does not discount the unreactive Lys in DDGS, although only the reactive Lys is available for use by animals. By measuring the ileal digestibility of only the reactive Lys, it is expected that estimation of the amount of bioavailable Lys in DDGS will be more accurate. The objective of this experiment, therefore, was to test the hypothesis that the concentrations of AID and SID of reactive Lys are lower than the concentrations of AID and SID of total Lys in DDGS. Twelve DDGS sources, diets containing each of these 12 DDGS sources, and ileal digesta from pigs fed these diets were obtained from two previous experiments. Samples were guanidinated with O-methylisourea and analyzed for the concentration of homoarginine. It was assumed that only the reactive Lys, but not the unreactive Lys, would be transformed to homoarginine. This procedure, therefore, allows the separate measurement of reactive and unreactive Lys in DDGS-containing diets and ileal digesta. Subsequently, the ileal digestibility of reactive Lys can be calculated. The AID and SID of reactive Lys (percent) and the concentration of apparent ileal and standardized ileal digestible reactive Lys (g/kg) were then calculated and compared with the previously calculated values for total Lys. Results showed that only 76% of the total Lys in DDGS is reactive. The AID and SID of reactive Lys in DDGS (average = 60.1 and 66.9%, respectively) were similar to the AID and SID of total Lys (60.9 and 66.5%, respectively). When calculated as grams per kilogram, the concentration of standardized ileal digestible reactive Lys (3.9 g/kg) was lower (P < 0.05) than the concentration of standardized ileal digestible total Lys (5.1 g/kg). Thus, 24% of the concentration of standardized ileal digestible total Lys that was calculated using the conventional ileal AA digestibility procedure was unreactive Lys. The implication of these results is that the conventional AA digestibility procedure overestimates the concentration of digestible Lys in DDGS, and measurement of the concentration of digestible reactive Lys may more accurately estimate the amount of Lys in DDGS that is bioavailable to the pig.

Relative bioavailability of phosphorus in inorganic phosphorus sources fed to growing pigs

The relative bioavailability of P in 5 sources of inorganic P was determined using growing pigs. The 5 sources of inorganic P were dicalcium phosphate (DCP), monocalcium phosphate (MCP) containing 50% MCP (MCP50), MCP containing 70% MCP (MCP70), MCP containing 100% MCP (MCP100), and monosodium phosphate (MSP). A total of 11 diets were formulated. The basal diet was formulated to contain 0.10% P, and 10 additional diets were formulated by adding 0.07 or 0.14% P from each of the 5 P sources to the basal diet. Growing pigs (n = 44; initial BW: 16.8 ± 4.3 kg) were individually housed and randomly allotted to the 11 experimental diets. Feed was provided on an ad libitum basis throughout the 28-d experimental period. At the conclusion of the experiment, all pigs were killed, and 4 bones (i.e., the third and fourth metacarpals on both front feet) were harvested. Bone-breaking strength, bone ash, and Ca and P concentrations were determined. The concentration of bone ash increased (P < 0.05) as MCP50, MCP70, MCP100, or MSP were added to the basal diet, and the concentration of bone P also increased (P < 0.05) as MCP70, MCP100, or MSP were added to the basal diet. The relative bioavailability of P in each of the feed phosphates was determined using slope ratio methodologies based on breaking strength, and expressed relative to MSP. The slope of the regression line for diets containing MSP or MCP100 was steeper (P < 0.05) than the slope for pigs fed the diet containing DCP, but not different (P > 0.05) from that of pigs fed diets supplemented with MCP50 or MCP70. In conclusion, P in MSP and MCP100 is more bioavailable than P in DCP, but there were no differences within MCP sources.

Evaluation of the furosine and homoarginine methods for determining reactive lysine in rumen-undegraded protein

Three samples of soybean meal (SBM), 3 samples of expeller SBM (SoyPlus, West Central Cooperative, Ralston, IA), 5 samples of distillers dried grains with solubles (DDGS), and 5 samples of fish meal were used to evaluate the furosine and homoarginine procedures to estimate reactive Lys in the rumen-undegraded protein fraction (RUP-Lys). One sample each of SBM, expeller SBM, and DDGS were subjected to additional heat treatment in the lab to ensure there was a wide range in reactive RUP-Lys content among the samples. Furosine is a secondary product of the initial stages of the Maillard reaction and can be used to calculate blocked Lys. Homoarginine is formed via the reaction of reactive Lys with O-methylisourea and can be used to calculate the concentration of reactive Lys. In previous experiments, each sample was ruminally incubated in situ for 16 h, and standardized RUP-Lys digestibility of the samples was determined in cecectomized roosters. All rumen-undegraded residue (RUR) samples were analyzed for furosine and Lys; however, only 9 of the 16 samples contained furosine, and only the 4 unheated DDGS samples contained appreciable amounts of furosine. Blocked RUP-Lys was calculated from the furosine and Lys concentrations of the RUR. Both the intact feed and RUR samples were evaluated using the homoarginine method. All samples were incubated with an O-methylisourea/BaOH solution for 72 h and analyzed for Lys and homoarginine concentrations. Reactive Lys concentrations of the intact feeds and RUR were calculated. Results of the experiment indicate that blocked RUP-Lys determined via the furosine method was negatively correlated with standardized RUP-Lys digestibility, and reactive RUP-Lys determined via the guanidination method was positively correlated with standardized RUP-Lys digestibility. Reactive Lys concentrations of the intact samples were also highly correlated with RUP-Lys digestibility. In conclusion, the furosine assay is useful in predicting RUP-Lys digestibility of DDGS samples, and the guanidination procedure can be used to predict RUP-Lys digestibility of SBM, expeller SBM, DDGS, and fish meal samples.

Evaluation of corn grain with the genetically modified input trait DAS-59122-7 fed to growing-finishing pigs.

A growth performance experiment was conducted to assess the feeding value of a double-stacked transgenic corn grain for growing-finishing pigs. The genetically modified corn grain contained event DAS-59122-7, which expresses the Cry34/35Ab1 binary insecticidal protein for the control of corn rootworm. This modified transgenic grain is resistant to western corn rootworm and is also tolerant to herbicides containing the active ingredient glufosinate-ammonium. The modified grain (59122), a nontransgenic near-isoline grain (control corn), and a commercial corn (Pioneer brand hybrid 35P12) were grown in a 2005 production trial in individually isolated plots that were located 201 m apart. A total of 108 pigs were allotted to corn-soybean meal diets containing 1 of the 3 grains as the sole source of corn. There were 3 pigs per pen and 12 replicate pens per treatment. Pigs were fed grower diets from 37 to 60 kg, early finisher diets from 60 to 90 kg, and late finisher diets from 90 to 127 kg. Within each phase, data for ADG, ADFI, and G:F were calculated. At the conclusion of the experiment, pigs were slaughtered and data for carcass quality were collected. Differences between 59122 and the control corn were evaluated, with statistical significance at P<0.05. No differences in ADG, ADFI, or G:F between pigs fed the control corn and pigs fed the modified corn were observed during the grower, early finisher, or late finisher phases. For the entire experimental period, no difference between pigs fed the control and the 59122 corn were observed for final BW (128.9 vs. 127.1 kg), ADG (1.02 vs. 1.00 kg), ADFI (2.88 vs. 2.80 kg), or G:F (0.356 vs. 0.345 kg/kg). Likewise, no differences in dressing percentage (76.48 vs. 76.30%), LM area (49.8 vs. 50.4 cm(2)), 10th-rib back fat (2.20 vs. 2.12 cm), and carcass lean content (52.9 vs. 53.4%) were observed between pigs fed the control and the 59122 corn grain. It was concluded that the nutritional value of the modified transgenic corn grain containing event DAS-59122-7 was similar to that of the nontransgenic near-isoline control.