Nutrient utilisation and metabolic adaptations to high proportions 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 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 amino acids in diets needed to meet the amino acid requirement of the animals is increased the lower the crude protein concentration is. Animals therefore ingest more free relative to peptide-bound amino acids. Absorptive processes are different for free and peptide-bound amino acids. Beyond that, there are post-absorptive differences caused by feeding free and peptide-bound amino acids. Some of these post-absorptive differences hitherto are theoretically derived. Their actual relevance for the utilisation of amino acids, however, is unclear.The aim of this project is to investigate the relevance of asparagine and glutamine supply as well as a challenged acid-bases in broiler chickens as possible causes for reduced nutrient utilisation when high proportions of free amino acids are fed. Metabolic adaptations to high proportions of free amino acids in diets are to be determined and adaptation limits are to be identified. Conclusions on adaption periods and a potentially existing highest possible proportion of free amino acids in diets without affected N utilisation efficiency and growth are to be drawn.The main hypotheses to be tested in this project are:a) There is a maximum level to which peptide-bound amino acids can be replaced with free amino acids without affecting N utilisation efficiency because adaptive processes are limited. This maximum level is higher when diets with high proportions of free amino acids contain asparagine and glutamine.b) The acid-base balance of animals is affected towards acidity when dietary proportions of free amino acids are high. This effect is less pronounced when diets with high proportions of free amino acids contain asparagine and glutamine.c) Blood metabolites give information which adaptive processes to high proportions of free amino acids in diets are active and point to adaptive processes which are unknown by now. This project comprises three consecutive trials. Amino acid digestibility of diets and ingredients is determined in the first trial to allow for identical digestible amino acid concentrations in the following trials. In the second trial, the maximum level to which peptide-bound amino acids can be replaced with free amino acids without affecting N utilisation efficiency is determined. On this basis, a maximum replacement level without affected N utilisation efficiency is compared to a higher replacement level in the third trial. Measurements are made in close time sequence after changeover from a diet containing ordinary proportions of free amino acids to identify metabolic adaptations and causes for undesirable consequences of high dietary proportions of free amino acids.

• DFG Programme: Research Grants