Browsing by Subject "Amino acid digestibility"

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Bestimmung präcecaler Verdaulichkeitskoeffizienten für heimische Energie- und Proteinfuttermittel für die Bio-Hühnermast
(2016) Ritteser, Carolin; Grashorn, Michael
To improving the supply of slow growing broiler chicken in organic poultry production with essential amino acids the ileal digestibility (ID) of 15 organically cultivated feedstuffs was determined using a linear regression approach. The ID was determined for three and six week old chickens. The feedstuffs included common cereal species such as wheat, rye, spelt and summer barley, hull-less cereals such as naked barley and naked oats, forgotten cereals or pseudo-cereals such as brown top millet, pearl millet and buckwheat but also corn silage, strip waste of lentils, alfalfa leaves, and clover grass silage (extruded and untreated). The cultivars were added to a basal diet in 3 concentrations in exchange to corn starch. Therefore, the increase for crude protein (CP) and amino acids (AA) resulted from the cultivar only. Titanium dioxide was used as an indigestible marker. Each diet was fed ad libitum between day 15 and 21 d of age to 6 pens of 15 chickens or between day 36 and 42 d of age to 6 pens of 6 chickens, each. On day 21 and/or day 42 birds were killed by carbon dioxide, the chymus was collected and pooled for the 15 or 6 chickens per pen, respectively and analyzed on pen basis. Contents of crude protein, amino acids and titanium dioxide have been determined. The slope of the regression line between the amount of AA intake by feed and the amount of AA digested up to the ileum is considered to be the true ileal digestibility. The crude nutrient contents of the organically grown feedstuffs show different results in comparison to conventionally grown ones. The highest crude protein content was determined for lentils, followed by clover grass silage and dried alfalfa leaves. However, the alfalfa leaves also showed the highest content of crude fiber. Brown top millet, pearl millet, clover grass silage and alfalfa leaves contained the highest amount of methionine. The highest lysine contents were found for lentils, clover grass silage and alfalfa leaves. Values for digestibility of crude protein and amino acids varied strongly among the feedstuffs. Rye, spelt and the clover grass silages were digested only poorly by both, the three and the six week old broilers. This was probably caused by an increased content of antinutritional substances and crude fiber. Extrusion didn´t have any positive effect on the amino acids digestibility of the clover grass silage, it rather impaired digestibility. For buckwheat and clover grass silage the high contents of crude protein and amino acids were compensated by poor digestibility. Brown top millet, pearl millet, strip waste of lentils and especially alfalfa leaves turned out to be appropriate feedstuffs for an adequate protein and amino acids supply in broiler nutrition. Due to the high fiber content alfalfa leaves should be used carefully in the diet. Their high crude fiber content causes an increase in feed volume and this may result in a too low feed intake of broilers to fulfill their nutritional requirements. This again can cause growth disturbances. In general, digestibility values for the organically grown feedstuffs were found to be similar to the values of conventionally grown feedstuffs.
Relevance of amino acid digestibility for the protein utilization efficiency in poultry
(2022) Siegert, Wolfgang; Siegert, Wolfgang
One aim of poultry nutrition research that has been pursued for decades is to decrease the ingested protein relative to the protein accreted in animal body weight or eggs, which is described in the key figure ‘protein utilization efficiency’. Increasing protein utilization efficiency aims to ensure global food and water security and to minimize the effects of excreted nitrogenous compounds on the environment and the health of animals and humans. Protein utilization efficiency can be increased by adjusting the supply of digestible amino acids to animals relative to the requirement for digestible amino acids. The predictability of amino acid digestibility of feed ingredients is a prerequisite to achieve this goal. This habilitation thesis puts knowledge gained from studies on methods of amino acid digestibility determination, influences on amino acid digestibility, and variation in amino acid digestibility within feed ingredients into the context of predictability of amino acid digestibility. Methodological, dietrelated, and animal-related influences that considerably determine amino acid digestibility are presented and evaluated. This includes feed intake, feed provisioning, feed processing, chemical composition of feed ingredients, feed enzymes, and microbiota in the digestive tract. Cropping conditions influencing amino acid digestibility are also addressed. The gained insights may contribute to make amino acid digestibility more predictable in the future. Recent attempts to predict amino acid digestibility, however, have not been sufficiently accurate to fulfill the aim of being able to formulate diets according to the requirement for digestible amino acids in practice. Suggestions for future strategies to work toward a more accurate predictability of amino acid digestibility are included. Model calculations show that increasing amino acid digestibility can considerably raise protein utilization efficiency. When amino acid digestibility is increased by an influence not related to the feed ingredient providing amino acids (e.g., supplemented enzymes), increasing amino acid digestibility by 1 percentage point raises the protein utilization efficiency by ~0.43 percentage points. An increase in protein utilization efficiency of up to 0.5 percentage points can be expected when amino acid digestibility is increased by selecting variants of a feed ingredient for higher amino acid digestibility. The thesis concludes with a critical examination of the general perception that higher amino acid digestibility and maximized protein utilization efficiency are advantageous. Situations in which lower amino acid digestibility and smaller protein utilization efficiency provide benefits are discussed.
Variability of amino acid digestibility of cereal grains in laying hens
(2017) Zuber, Tobias; Rodehutscord, Markus
It was the objective of this doctoral thesis to generate a comprehensive data set of AA digestibility values of cereal grains in laying hens by using a strictly standardized assay procedure. Additionally, the suitability of two approaches to predict AA digestibility was examined. For this purpose, 80 genotypes of triticale, rye, corn, and wheat grains (n = 20 each) were grown as part of the “GrainUp” project. Apart from corn, the cereal species were grown under identical environmental conditions. The grain samples were comprehensively analyzed according to their physical properties, chemical composition, and gross energy concentration. The concentration of crude protein in the grain samples of triticale, rye, corn, and wheat was in the range of 113-138, 108-127, 78-112, and 125-162 g/kg dry matter, respectively. Additionally, the in vitro solubility of nitrogen (N) was determined in the grains after pretreatment with porcine pepsin and pancreatin. The animal trial comprised 16 Latin Squares (6x6), distributed among six subsequent runs. Thus, each run contained two to three Latin Squares. Cecectomized laying hens were individually housed in metabolism cages and fed either on a basal diet containing 500 g/kg cornstarch or one of the 80 cereal diets, with the cornstarch being replaced with a grain sample, for eight days. During the last four days, feed intake was recorded and excreta were collected quantitatively twice daily. After each collection period, the hens were group-housed in a floor pen for two days and offered a conventional layer diet. Amino acid digestibility of the grain samples was calculated using a linear regression approach. Relationships between AA digestibility and single analyzed fractions or the in vitro solubility of N of the cereal grains were examined by calculating Pearson product-moment correlation coefficients. Prediction equations to estimate AA digestibility were calculated by multiple regression analysis using a stepwise selection approach. Therefore, the variables were pooled according to their characteristics, and the prediction equations were calculated for the digestibility of each AA using each pool. The variables were offered in a linear or linear plus quadratic fashion and classified as significant predictors at P<0.10. The equations were assessed based on the adjusted R² and the root-mean-square error. The AA digestibility varied widely within and among the cereal species. The mean digestibility of lysine was 74% (digestibility range: 68-80%), 49% (35-59%), 79% (64-85%), and 80% (69-87%) for triticale, rye, corn, and wheat grains, respectively. A similar ranking was observed for methionine with a mean digestibility of 83% (digestibility range: 77-86%), 67% (57-75%), 91% (86-94%) and 84% (70-93%) for triticale, rye, corn, and wheat grains, respectively. Correlation analysis showed inconsistent results within and across the cereal species. Among the physical characteristics, significant correlations were detected for the thousand seed weight and the digestibility of a few AA in wheat, and for the test weight and the digestibility of a few AA in rye and corn. Significant correlations between NSP fractions and the digestibility of essential AA were detected only for rye grains. In this crop, the concentration of arabinoxylans and total NSP in the grains was negatively correlated with the digestibility of arginine, leucine, phenylalanine, and threonine. The concentration of crude protein in corn grains was positively correlated with the digestibility of essential AA, except isoleucine, tryptophan, and valine. In contrast, only a few significant positive correlations between crude protein concentration and essential AA digestibility were found for triticale and rye grains. No significant correlations were found for wheat grains in this regard. The in vitro solubility of N was negatively and positively correlated with the digestibility of a few AA in triticale and rye grains, respectively. The accuracy of the predictive equations was generally low (adjusted R² below 0.7 in most cases), and varied considerably between both pools of variables for the same AA and the same pool of variables for different AA. Thus, single or several physical or chemical characteristics could not explain the variation in AA digestibility in laying hens and the development of prediction equations sufficiently precise for the practical application was not possible.