Standardized ileal digestibility of amino acids in eight genotypes of barley fed to growing pigs

Prediction of protein and amino acid composition and digestibility in individual feedstuffs and mixed diets for pigs using near-infrared spectroscopy

Knowledge of the amounts and digestibility of amino acids in pig feedstuffs is essential for calculating the appropriate inclusion level in a complete diet. Wet chemical analysis and in vivo digestibility trials are time-consuming and costly and cannot be used for routine assessment. Near-infrared spectroscopy (NIRS) offers a rapid, cost effective and environmentally friendly method for evaluating feedstuffs. Calibrations models were developed using NIRS to predict the content of crude protein and 18 amino acids from a wide range of feedstuffs used in pig production (n = 607). The samples ranged from single feed ingredients (containing amino acids from 0.3 to 129.8 g/kg of dry matter) to feed mixtures (containing amino acids from 1.2 to 53.2 g/kg of dry matter). The predictive ability of the calibrations was tested with an independent dataset (n = 150) and with cross-validation. Furthermore, we compare these calibrations with calibrations developed on more narrowly defined groups of samples and with predictions from regression analysis of crude protein. The models were able to predict the concentrations of crude protein and 18 amino acids with good levels of precision and high coefficients of determination for calibration (RSQ ^CAL) from 0.91 to 0.99 and validation (RSQ^VAL) from 0.87 to 0.97. Calibration models were able to predict all amino acids except tryptophan and valine with greater accuracy than those from protein regression. We also developed calibration models to predict the apparent ileal and total tract digestibility of protein and amino acids. With the exception of tryptophan, RSQ values (>0.7) and standard error of cross validation (SECV) values (<5%) were obtained for the digestibility of most of the amino acids. In conclusion, NIRS can be used to predict crude protein and amino acid concentrations from a wide range of single ingredients and feed mixtures used for pig diets without separate models for each feedstuff. The digestibility of protein and amino acids can be predicted with an acceptable accuracy to be useful in formulating pig diets.

Comprehensive overview of the quality of plant- And animal-sourced proteins based on the digestible indispensable amino acid score

Indispensable amino acid (IAA) composition and standardized ileal digestibility (SID) of five animal- and 12 plant-based proteins were used to calculate their respective Digestible Indispensable Amino Score (DIAAS) according to the three age categories defined by the Food and Agriculture Organization (FAO). Mean IAA content and mean SID obtained from each protein dataset were subsequently used to simulate optimal nutritional quality of protein mixtures. Datasets revealed considerable variation in DIAAS within the same protein source and among different protein sources. Among the selected protein sources, and based on the 0.5- to 3-year-old reference pattern, pork meat, casein, egg, and potato proteins are classified as excellent quality proteins with an average DIAAS above 100. Whey and soy proteins are classified as high-quality protein with an average DIAAS ≥75. Gelatin, rapeseed, lupin, canola, corn, hemp, fava bean, oat, pea, and rice proteins are classified in the no quality claim category (DIAAS <75). Potato, soy, and pea proteins can complement a broad range of plant proteins, leading to higher DIAAS when supplied in the form of protein mixtures and at specific ratios. Such complementarity highlights the potential to achieve an optimal nutritional efficiency with plant proteins alone.

Evaluation of analytical and statistical approaches for predicting in vitro nitrogen solubility and in vivo pre-caecal crude protein digestibility of cereal grains in growing pigs

Different analytical (enzyme system and near-infrared spectroscopy (NIRS)) and statistical (single and multiple regressions) approaches were used to predict in vivo standardized pre-caecal digestibility (PCD) of crude protein (CP) and amino acids (AA) in cereal grains for growing pigs as well as in vitro nitrogen (N) solubility. Furthermore, different chemical and physical characteristics were categorized (e.g. crude nutrients, AA, minerals, fibre components or combinations of these) and used for generating prediction equations. There were strong linear relationships (p < .05) between in vivo PCD of CP and essential AA and in vitro N solubility when grain species was considered as covariate in the model. Predicting in vivo PCD values using various chemical and physical characteristics produced inconsistent results among different grain species and AA and could therefore not be used for predicting PCD. It is possible to predict in vitro N solubility from chemical and physical characteristics for some grain species. However, the relationships between some of these categories and the in vitro N solubility were not consistent and not always causative or physiologically explainable. The R² of NIRS for predicting in vitro N solubility was at a relatively high level (up to R²  = 0.80). This level of R² indicates that a classification of the grain samples in, for example, high, medium and low in vitro N solubility levels is possible, but it does not allow for a quantitative prediction of the in vitro N solubility. In conclusion, the present database can be used for establishing a ranking of different cereal grain species for PCD of CP and essential AA values. However, it was not possible to create clear prediction equations for in vivo or in vitro digestibility values. Therefore, greater variation within grain species, for example due to different growing and harvesting conditions, is warranted for predicting PCD values of individual grain samples.

Ileal starch digestibility of different cereal grains fed to growing pigs

The objective of the present study was to determine, in growing pigs, the ileal starch digestibility and ileal digestible starch content of 8 different genotypes of barley, rye, triticale, and wheat each. Therefore, 4 experiments were conducted with 34 ileally cannulated growing pigs (initial BW of 24 to 32 kg) in total. The experimental diets were formulated to contain 1 of the 8 genotypes of each cereal grain at an inclusion level of 95%. Cereal grains were ground through a 2-mm sieve and were the sole dietary source of starch. All diets were supplemented with plant oil, minerals and vitamins, and titanium dioxide as an indigestible marker. The experiments were arranged either as a row-column design with 8 periods of 6 d each and 9 pigs (for barley and wheat) or according to an 8 × 8 Latin square design with 8 periods of 6 (rye) or 7 d (triticale) and 8 pigs. Experimental periods comprised 4 (barley, rye, and wheat) or 5 d (triticale) for adaptation followed by 2 d for ileal digesta collection. The daily feed intake amounted to 4% of pigs' average BW, corresponding to about 3 times the animals' energy requirement for maintenance (106 kcal of ME [as-fed basis]/kg of metabolic BW). Ileal starch digestibility was different ( < 0.05) within barley and triticale genotypes, with values ranging between 90.1 and 95.0% for barley and between 96.5 and 98.1% for triticale and tended to differ within rye genotypes ( < 0.1). Ileal digestible starch content was different ( < 0.05) within all cereal grains. On average, ileal starch digestibility amounted to 92.7, 95.0, 97.3, and 92.2% for barley, rye, triticale, and wheat, respectively, and was different among cereal grains ( < 0.001). Average ileal digestible starch content was greatest ( < 0.001) in triticale (68.3%, DM basis) followed by wheat (66.1%, DM basis), rye (61.1%, DM basis), and barley (57.6%, DM basis). Differences in ileal starch digestibility and ileal digestible starch content within and among grain genotypes may reflect variations in contents of several fiber fractions such as NDF, ADF, and nonstarch polysaccharides (NSP). For most cereal grains, ileal starch digestibility and ileal digestible starch content decreased ( < 0.05) with increasing contents of soluble, insoluble, and total NSP. In conclusion, in the present study, triticale is superior when compared with the other cereal grains due to its relatively low fiber and high starch content and its high ileal starch digestibility values.

Variations in the chemical composition and standardized ileal digestibility of amino acids in eight genotypes of triticale fed to growing pigs

The study was conducted to determine the chemical composition, physical characteristics, and standardized ileal digestibility (SID) of CP and AA of 8 currently available genotypes of triticale fed to growing pigs. The genotypes included Grenado, Cando, Agostino, Massimo, Tarzan, HYT Prime, SW Talentro, and Cultivo. Eight barrows with an initial BW of 31 ± 2 kg were fitted with simple T-cannulas at the distal ileum and allotted to an 8 × 8 Latin square design with 8 periods of 7 d each and 8 assay diets. The N-free method was used to determine basal ileal endogenous CP and AA losses. The 8 assay diets contained 1 of 8 triticale genotypes as the sole source of CP and AA. The triticale genotypes were grown under identical environmental conditions on the same site. Among the 8 genotypes, contents of CP ranged from 104.7 to 118.1 g/kg (as-fed basis). The content of total nonstarch polysaccharides and NDF ranged, on an as-fed basis, from 84.6 to 99.5 g/kg and from 88.4 to 149.0 g/kg, respectively. Among the 8 genotypes, SID of CP ranged from 81% in Grenado to 85% in Massimo and Tarzan. The SID of CP and AA did not differ among triticale genotypes except for SID of Arg, Glu, and Gly ( < 0.05). The mean SID of CP, Lys, Met, and Trp was 4, 4, 4, and 1 percantage units less and SID of Trp was 5 percantage units greater compared with values in current feed tables. Among the 8 triticale genotypes, standardized ileal digestible content (cSID) of CP followed total CP content and ranged from 84.8 to 98.7 g/kg (as-fed basis), with the lowest ( < 0.001) values for Grenado and the greatest ( < 0.001) values for SW Talentro and Cultivo. For CP and most AA, cSID linearly decreased as the content of total, soluble, and insoluble β-glucans increased ( < 0.05) in the 8 genotypes of triticale. There was a positive correlation between thousand seed weight and cSID of CP and most AA ( < 0.01). These variables may help to predict cSID in triticale batches, whereas other nutrients are not suitable due to their low variation among the 8 genotypes. The present study provides data on chemical composition, physical characteristics, and SID of CP and AA of 8 triticale genotypes grown under similar conditions. However, as most of the present SID values are less than those in feed tables, future research is warranted to elaborate whether these differences are caused by experimental conditions or reflect a consistent decrease that needs to be accounted for in feed tables.

Determination of basal ileal endogenous losses and standardized ileal digestibility of amino acids in barley fed to growing pigs

BACKGROUND

Basal ileal endogenous amino acid (AA) losses (IAA_end) and standardized ileal digestibility (SID) values of cereal grains, such as barley, are apparently underestimated when determined according to the nitrogen (N)-free method. Regression analysis between the dietary apparent ileal digestible content (cAID) and total crude protein (CP) and AA can be considered as alternative approach to obtain more accurate values for IAA_end and SID of AA in cereal grains.

METHODS

Eight hulled barley genotypes were used, with barley being the only source of CP and AA in the assay diets. The diets contained 95 % as-fed of these eight barley genotypes each, ranging in CP content between 109.1 and 123.8 g/kg dry matter (DM). Nine ileally T-cannulated barrows, average body weight (BW) 30 ± 2 kg, were allotted to a row-column design comprising eight periods with 6 d each and nine pigs. On d 5 and the night of d 6 of every period, ileal digesta were collected for a total of 12 h. The IAAend and the SID were determined by linear regression analysis between cAID and total dietary CP and AA.

RESULTS

There exist linear relationships between cAID and total CP and AA (P < 0.001). The IAAend of CP, Lys, Met, Thr and Trp amounted to 35.34, 1.08, 0.25, 1.02 and 0.38 g/kg DM intake (DMI), respectively, which are greater compared to average IAAend determined previously under N-free feeding conditions. The SID of CP, Lys, Met, Thr and Trp was 90, 79, 85, 79 and 86 %, respectively, and was greater when compared to tabulated values. Moreover, these SID values were greater than those reported in literature, based on correction of apparent ileal digestibility (AID) of CP and AA for their IAA_end values. Summarized, the results of the present regression analysis indicate greater IAA_end in barley-based diets compared to those obtained by N-free feeding.

CONCLUSIONS

For low-protein feed ingredients like barley the regression method may be preferred over correction of AID values for their IAA_end determined under N-free feeding conditions, as intercepts and slopes of the linear regression equations between cAID and total dietary CP and AA provide direct estimates of IAA_end and SID of CP and AA in the presence of the assay feed ingredient.

Amino acid digestibility of different rye genotypes in caecectomised laying hens

This study investigated the variability of amino acid (AA) digestibility of rye grains in laying hens. Relationships between AA digestibility and physical properties (thousand seed weight, test weight, falling number, and extract viscoelasticity), chemical composition (proximate nutrients, non-starch polysaccharides, AA, minerals, and inositol phosphates), gross energy concentration, and in vitro solubility of nitrogen (N) of the grains were also examined. Twenty rye genotypes were grown under standardised agronomic and environmental conditions as part of a collaborative research project known as "GrainUp". Each genotype was added to a basal diet at 500 g/kg at the expense of maize starch to produce 20 rye diets. The experimental design comprised four Latin Squares (6 × 6) distributed over two runs, resulting in 12 experimental periods. Caecectomised laying hens (LSL-Classic) were individually kept in metabolism cages. Excreta were collected quantitatively for 4 d, and AA digestibility of the rye genotypes was determined using a regression approach. The digestibility of AA was generally low but varied significantly among the 20 rye genotypes, especially for Lys (digestibility range 35-59%), Met (57-75%), Thr (34-54%), and Trp (36-71%). Nevertheless, physical and chemical characteristics as well as the in vitro solubility of N correlated in only a few cases with AA digestibility. Multiple linear regression was used to calculate equations to predict AA digestibility based on the analysed characteristics. However, their explanatory power, as judged by the adjusted R(2), was not sufficiently precise for practical application (below 0.6 for most AA). In conclusion, the AA digestibility of rye grain is generally low and varies significantly between crop genotypes. Equations based on its physical and chemical characteristics are not sufficiently precise to be useful for feed formulation.