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Endogenous amino acid flow in the avian ileum: quantification using three techniques
V Ravindran1, L I Hew, G Ravindran
1Department of Animal Science, The University of Sydney, Camden, NSW 2570, Australia. V.Ravindran@massay.ac.nz
The British Journal of Nutrition
|August 31, 2004
Summary
Comparing protein-free, guanidinated casein (GuC), and enzyme hydrolyzed casein (EHC) diets for measuring endogenous amino acid (AA) flow in chickens, this study found GuC and EHC methods yield significantly higher AA flows than protein-free diets. These methods better reflect normal physiological conditions for ileal endogenous AA losses.
Area of Science:
- Animal Nutrition
- Digestive Physiology
- Nutrient Metabolism
Background:
- Accurate quantification of endogenous amino acid (AA) flow in the avian ileum is crucial for precise nutrient utilization studies.
- Traditional protein-free diet methods may underestimate ileal endogenous AA losses.
- Novel methods using specific protein sources are needed to better reflect physiological conditions.
Purpose of the Study:
- To compare the efficacy of three methods—protein-free diet, guanidinated casein (GuC), and enzyme hydrolyzed casein (EHC)—for quantifying endogenous amino acid (AA) flow in broiler chickens.
- To determine which method best represents endogenous AA losses under normal physiological conditions.
Main Methods:
- Growing broiler chickens (5 weeks old) were fed three distinct assay diets: a protein-free diet, a diet with GuC as the sole nitrogen source, and a diet with EHC as the sole nitrogen source.
- Ileal digesta were collected and analyzed for endogenous amino acid (AA) flow using each of the three dietary treatments.
Main Results:
- Endogenous AA flows determined by GuC and EHC methods were significantly higher (approximately 3-fold) than those determined by the protein-free diet.
- GuC and EHC methods yielded similar total endogenous AA flows, with the exception of arginine, which was lower with EHC.
- Dietary method influenced the AA composition of endogenous protein, notably affecting threonine, glutamic acid, lysine, arginine, and cystine concentrations.
Conclusions:
- Ileal endogenous nitrogen and amino acid flows are significantly enhanced by the presence of protein and peptides compared to protein-free conditions.
- Enzyme hydrolyzed casein (EHC) and guanidinated casein (GuC) methods provide a more accurate measurement of ileal endogenous losses in chickens under physiological conditions than protein-free diets.