Responses of the blood acid-base balance and blood plasma metabolomics of broiler chickens after change to diets with high free amino acid levels

• Published in: Poultry science 2024-08, Vol.103 (8), p.103956, Article 103956
• Main Authors: Ibrahim, Ahmad, Kenéz, Ákos, Pfannstiel, Jens, Klaiber, Iris, Rodehutscord, Markus, Siegert, Wolfgang
• Format: Article
• Language: English
• Subjects: acid-base balance; Acid-Base Equilibrium; acidosis; Amino Acids - blood; Amino Acids - metabolism; Animal Feed - analysis; Animal Nutritional Physiological Phenomena; Animals; broiler chicken; Chickens - blood; Chickens - physiology; Diet - veterinary; free amino acid; Male; METABOLISM AND NUTRITION; Metabolome; Metabolomics; Random Allocation
• ISSN: 0032-5791; 1525-3171; 1525-3171
• DOI: 10.1016/j.psj.2024.103956

Free amino acids (AA) are needed to fulfill the AA requirements of broiler chickens in diets low in CP. This study investigated whether the acid-base balance and the blood plasma metabolome are affected immediately after a change to diets with high free AA levels. Male broiler chickens received a starter diet with 164 g CP/kg and 80 g soy protein isolate/kg until d 7 post-hatch. From this day on, birds were offered a diet almost identical to the starter diet (0FAA) or 2 diets with 50% (50FAA) or 100% (100FAA) of the digestible AA from soy protein isolate substituted with free AA. Blood was sampled to determine the acid-base status and for untargeted metabolomics analysis on d 0, 1, 2, 4, 7, and 14 and d 1, 7, and 14 after diet change, respectively (n = 14 birds/treatment). Compared to 0FAA, blood pH was decreased on d 4 and 7 for 100FAA and on d 4 for 50FAA (P ≤ 0.019). On d 4, 7, and 14, bicarbonate, base excess, and total carbon dioxide were lower for 100FAA than for 0FAA (P ≤ 0.006). The partial pressure of carbon dioxide was higher for 50FAA than for 0FAA on d 4 (P = 0.047). Compared to 0FAA, chloride was higher for 100FAA on d 1, 2, 4, 7, and 14, and for 50FAA on d 1, 2, and 4 (P ≤ 0.030). In the metabolomics assay, 602, 463, and 302 metabolites were affected by treatment on d 1, 7, and 14, respectively (P < 0.050), but they did not indicate that metabolic pathways were affected. Flavonoids were the most consistently affected category of metabolites. The results indicated a metabolic acidosis for 100FAA from d 4 to 7 and a respiratory acidosis for 50FAA on d 4 after diet change. These types of acidosis were compensated later on in the experiment. The metabolomics analysis did not indicate that high free AA inclusion affected metabolic pathways.