Browsing by Subject "Protein utilization efficiency"

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    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.