Influencing the effects of high levels of free amino acids in feed for broiler chickens

• Applicant: Professor Dr. Wolfgang Siegert
• Subject Area: Animal Breeding, Animal Nutrition, Animal Husbandry
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 434519168

Reducing dietary crude protein concentrations with adequate amino acid (AA) supply of animals is desirable because the utilisation efficiency of dietary nitrogen (N) is increased and negative effects of livestock farming on the environment are decreased. The proportion of free AA in diets needed to meet the AA requirement of the animals is higher the lower the crude protein concentration is. Hence, animals ingest more free relative to peptide-bound AA. Absorptive processes are different for free and peptide-bound AA. Beyond that, there are post-absorptive differences caused by feeding free and peptide-bound AA. In the course of the project Si 2258/3-1, further fundamental research questions arose. In the previous project, an upper limit of free AA in the feed was determined upon substituting peptide-bound with free AA with an unchanged dietary concentration of digestible AA. Adaptation processes after a change to diets with high proportions of free AA were investigated. The aim of this follow-up project is to investigate open causes of effects on N utilisation efficiency and the acid-base balance when feeding high proportions of free AA in diets for broiler chickens. Adaptations of the metabolism to high proportions of free AA in diets will be focused in more detail than in the previous project. The main hypotheses to be tested are: a) Influences on the acid-base balance upon feeding high proportions of dietary free AA are less pronounced when the dietary supply with sodium bicarbonate is higher. b) A proteomics study of small intestinal tissues shows a relevant influence of the proportion of free AA in diets and provides information about previously unknown adaptation processes of the tissues. c) It is important to consider asparagine in diet formulation when peptide-bound AA are substituted with free AA, while a relevance of glutamine in this context is not confirmed. d) The fractional protein synthesis rate is lower when dietary peptide-bound are substituted with free AA, particularly when asparagine and glutamine are fed deficiently. The project consists of three consecutive experiments. First, the AA digestibility of diets is determined in order to enable equal dietary concentrations of digestible AA in the following experiments. The second experiment examines whether an influence on the acid-base balance upon substituting peptide-bound with free AA can be alleviated or even eliminated by increasing dietary sodium bicarbonate. Finally, the third experiment examines which effects the supply of the AA glutamic acid, glutamine, aspartic acid and asparagine has when peptide-bound AA are substituted with free AA. Measurements are carried out at close intervals after change from diets with common free AA levels in order to identify metabolic consequences and adjustments of high dietary levels of free AA.

• DFG Programme: Research Grants