Oven drying of ileal digesta from growing pigs reduces the concentration of AA compared with freeze drying and results in reduced calculated values for endogenous losses and elevated estimates for ileal digestibility of AA

The pig is an excellent model to determine amino acid digestibility of human foods and to generate data needed to meet human amino acid requirements

The protein value of any food item is determined by the quantity and ileal digestibility of indispensable amino acids in that food. To determine the ileal digestibility of amino acids, an animal model needs to be used, and the pig is the preferred model because values for ileal digestibility obtained in pigs are representative of values obtained in humans. In addition, pigs are omnivorous animals like humans, they are meal eaters, they consume most diets that humans consume, they are easy to work with, and they can be used for repeated determinations of digestibility in many foods. It is, therefore, possible to use pigs to establish a database with digestibility values for human foods and by correcting digestibility values obtained in pigs for the basal endogenous losses of amino acids, it is possible to calculate true ileal digestibility values that are additive in mixed meals. As a consequence, the protein quality of a meal consisting of several food items can be calculated based on digestibility values obtained in pigs. Future work needs to focus on expanding existing databases for amino acid digestibility in foods to include more food items, which will make it possible to estimate the amino acid value of more mixed meals. It is also necessary that the amino acid values in mixed meals be related to requirements for digestible indispensable amino acids in the individuals consuming the meals. The current contribution describes the basic steps in determining amino acid digestibility in human foods using the pig as a model and also outlines future steps needed to further improve amino acid nutrition in humans.

Apparent digestibility of energy and nutrients and efficiency of microbial phytase is influenced by body weight of pigs

An experiment was conducted to test the hypothesis that regardless of pig body weight (BW), increasing dietary phytase results in increased phytate degradation and improved digestibility of minerals, amino acids (AA), and gross energy (GE). Eighteen pigs were equipped with a T-cannula in the distal ileum and allotted to a triplicated 6 × 3 Youden square design with six diets and three collection periods of 7 d, for a total of nine replicate pigs per diet. This design was repeated four times to simulate four production phases, and there was a 7-d resting period before each collection phase started (BW at start of collections: 29.3, 53.6, 85.1, and 114.4 kg for phases 1, 2, 3, and 4, respectively). Six corn-soybean meal diets were formulated by including 0, 250, 500, 1,000, 2,000, or 4,000 phytase units/kg feed (FTU). The six diets were used throughout the experiment. Samples of feces and ileal digesta were collected in each period. Results indicated that regardless of pig BW, increasing inclusion of phytase increased (quadratic; P < 0.05) apparent ileal digestibility (AID) of crude protein (CP) and most AA, increased apparent total tract digestibility (ATTD) of Ca, P, K, Mg (linear and quadratic; P < 0.05), and Na (linear; P < 0.05), but decreased (linear and quadratic; P < 0.05) AID and ATTD of GE. In all phases, ileal concentrations of inositol phosphate (IP) 6, IP5, IP4, and IP3 decreased (linear and quadratic; P < 0.05), whereas ileal inositol increased (linear and quadratic; P < 0.05) with increasing dietary phytase. However, as pig BW increased, AID of GE, CP, and AA increased (linear, P < 0.05), and the AID of a few AA (Met, Phe, Thr, Trp, Ala, Asp, Gly, and Ser) also increased quadratically (P < 0.05). The ATTD of GE, K, and Mg increased (linear and quadratic; P < 0.05), but ATTD of Ca and Na (linear; P < 0.05) and of P (linear and quadratic; P < 0.05) decreased as pig BW increased. Ileal IP6 and IP3 (linear and quadratic; P < 0.05) and ileal IP5 and IP4 (linear; P < 0.05) increased, whereas ileal inositol decreased (linear; P < 0.05) as pig BW increased. In conclusion, regardless of pig BW, increasing dietary phytase increased phytate degradation and inositol release in the small intestine, and consequently increased mineral and AA digestibility. Older pigs have reduced Ca, P, and Na digestibility, but increased K, Mg, AA, and GE digestibility compared with younger pigs. The efficiency of dietary phytase to degrade phytate appears to decrease as pigs get older.

Lack of interactive effects between diet composition and acid addition with drying method on amino acid digestibility values in porcine ileal digesta

Two experiments were conducted to determine the effect of oven drying (OD) or freeze drying (FD) on apparent ileal digestibility (AID) of AA in diets fed to pigs. In experiment 1, 15 barrows (88.4 ± 6.4 kg) were allotted to either a corn starch-soybean meal (CST), potato starch-soybean meal (PST), or corn-soybean meal (CSBM) diet, over 2 collection periods. Following collection, samples were pooled within pig and subdivided into either OD or FD, resulting in 10 observations per diet by drying-method combination. In experiment 2, 11 barrows (63.3 ± 3.8 kg) were fed a CST diet, and, following collection, samples were pooled within pig and subdivided and either adjusted to pH 4 or remain unadjusted. Subsets of these samples were then subdivided to be either FD or OD, resulting in 11 observations per pH level by drying-method combination. OD was accomplished by drying samples in a forced air oven at either 100 °C (experiment 1) or 75 °C (experiment 2). In experiment 1, there was no diet type by drying-method interactions noted for any of the AA (P > 0.10).OD resulted in a higher AID of AA compared with samples which were FD (P ≤ 0.10), for all AA except for Gly and Tyr. Averaged across all AA, AID of AA was 3.3% greater if the sample was OD compared with FD. Differences in AID of AA among the 3 diets were noted for all AA (P ≤ 0.07), except for Cys (P = 0.33), due to the fact that CST and PST diets only contained soybean meal (SBM) as an AA-providing ingredient while the CSBM diet contained both corn and SBM. Pigs fed the PST diet had greater SID for all AA compared with pigs fed the CST diet (P ≤ 0.05), except for His, Lys, Cys, and Glu. In experiment 2, there were no pH-adjustment by drying-method interactions noted on AID for any of the AA (P > 0.10). Adjusting ileal digesta to a pH of 4.0 had little effect on AID for most of the AA, except for a lowered AID of Arg, His, Lys, Trp, and Ser (P ≤ 0.10). OD resulted in a higher AID for all AA (P ≤ 0.09) except for Ile, Thr, Val, Ala, Asp, Glu, and Gly. Averaged across all AA, the increase in AID of AA was 1.7% greater if the sample was OD compared with FD. On average, OD of ileal digesta resulted in a 2.5% greater estimate of AID of AA compared with samples that were FD, and was not diet-, pH-, or AA-dependent. Because the majority of the data on AA digestibility are based on FD, a bias factor may be necessary to adjust AA digestibility data obtained on an OD-basis relative to an FD-basis for use in feed formulation.

Amino acid composition and digestible amino acid content in animal protein by-product meals fed to growing pigs1

An industry survey and animal experiment were conducted to evaluate the amino acid (AA) compositional variability and standardized ileal digestibility (SID) of AA in animal protein by-products fed to growing pigs. Animal protein by-product meals (212) were categorized into 8 groupings (blood meal, chicken by-product meal, chicken meal, feather meal, meat and bone meal, meat meal, poultry by-product meal, and poultry meal) and analyzed for total AA. Amino acid analysis among (e.g., Lys in blood meal averaged 9.20% compared with 2.31% for feather meal, DM basis) and within (e.g., Lys range of 1.54% in blood meal and 1.44% in feather meal, DM basis) the by-product classifications varied as expected, but on average the total AA values were similar to that reported in the literature. For the determination of the SID of AA, 15 barrows (average initial and final BW of 31.6 and 78.7 kg, respectively) were fitted with a T-cannula in the distal ileum and allotted to 15 diets over nine 7-d periods, resulting in 9 replications per diet. Pigs were fed a basal diet based on soybean meal and dehulled-degermed corn, 13 diets containing 17.5% animal protein by-product meal to partially replace a portion of the soybean meal and dehulled-degermed corn in the basal diet, or a N-free diet. Pigs were re-allotted to diets based on minimizing the number to times that the N-free diet would precede or follow feeding either of the blood or feather meal diets because of concern with inadequate diet consumption, as well as to prevent diets from being re-fed to the same pig during the next or subsequent periods. Values for the apparent ileal AA digestibility of each diet were determined, adjusted to SID based upon the endogenous AA losses determined by feeding the N-free diet, and the SID of AA in each animal protein by-product meal calculated using the difference procedure. The SID of AA varied among (e.g., SID of Lys averaged 91% in chicken meal but 47% in feather meal) and within (e.g., SID of Lys in three meat and bone meals was 80%, 71%, and 54%) the animal protein by-product meals, as would be expected and are consistent with variation reported in the literature. Overall, the data provide total AA composition for 212 samples and SID of AA for 13 samples of animal protein by-product meals, including data on their variability, which is critical for their use in feed formulation programs.

Torula yeast has greater digestibility of amino acids and phosphorus, but not energy, compared with a commercial source of fish meal fed to weanling pigs

Three experiments were conducted to test the hypothesis that the standardized ileal digestibility (SID) of AA, concentrations of DE and ME, and the standardized total tract digestibility (STTD) of P in a source of torula yeast are not different from values obtained in Menhaden fish meal. In experiment 1, six weanling barrows (initial BW: 11.7 ± 0.4 kg) were prepared with a T-cannula in the distal ileum and allotted to a replicated 3 × 3 Latin square design with 3 diets and 3 periods. In each period, there were 5 d of adaptation and 2 d of collection. Two cornstarch-based diets using the torula yeast or fish meal as the sole source of AA and a N-free diet were formulated. The SID of CP and all AA was greater (P < 0.05) in torula yeast than in fish meal. In experiment 2, 24 weanling barrows (initial BW: 14.4 ± 1.1 kg) were individually housed in metabolism crates and allotted to a corn-based diet or 2 diets based on a mixture of corn and torula yeast or corn and fish meal. Feces and urine samples were collected for 4 d following a 5-d adaptation period. There were 8 replicate pigs per diet and fecal and urine materials were collected. Results of this experiment indicated that there were no differences in the concentration of DE and ME (DM basis) between torula yeast and fish meal. In experiment 3, a total of 32 weanling barrows (initial BW: 11.9 ± 1.1 kg) were allotted to 4 diets and 8 replicate pigs per diet. Pigs were placed in individual metabolism crates. The torula yeast or fish meal were used in 2 diets containing either 0 or 500 units of microbial phytase. Feces samples were collected as described for experiment 2. The STTD of P in torula yeast was greater (P < 0.05) than in fish meal, but regardless of ingredient, there was no effect of the inclusion of phytase in the diets. In conclusion, the SID of AA and the STTD of P in torula yeast is greater than in fish meal, but values for the concentration of DE and ME in torula yeast are not different from those in fish meal. Therefore, the torula yeast that was used in the present experiments may be included at the expense of fish meal in diets fed to weanling pigs if the concentration of standardized ileal digestible AA is considered in the formulation.