The 15N-leucine single-injection method allows for determining endogenous losses and true digestibility of amino acids in cecectomized roosters

Abstract

This study was conducted to assess the influence of dietary protein content in poultry when using the 15N-leucine single-injection method to determine endogenous amino acid losses (EAALs) in poultry. Forty-eight cecectomized roosters (2.39 ± 0.23 kg) were randomly allocated to eight dietary treatments containing protein levels of 0, 3%, 6%, 9%, 12%, 15%, 18% and 21%. Each bird was precisely fed an experimental diet of 25 g/kg of body weight. After feeding, all roosters were subcutaneously injected with a 15N-leucine solution at a dose of 20 mg/kg of body weight. Blood was sampled 23 h after the injection, and excreta samples were continuously collected during the course of the 48-h experiment. The ratio of 15N-enrichment of leucine in crude mucin to free leucine in plasma ranged from 0.664 to 0.763 and remained relatively consistent (P > 0.05) across all treatments. The amino acid (AA) profiles of total endogenous AAs, except isoleucine, alanine, aspartic acid, cysteine, proline and serine, were not influenced (P > 0.05) by dietary protein contents. The predominant endogenous AAs in the excreta were glutamic acid, aspartic acid, threonine, serine and proline. The order of the relative proportions of these predominant AAs also remained relatively constant (P > 0.05). The endogenous losses of total AAs determined with the 15N-leucine single-injection method increased curvilinearly with the dietary protein contents. The true digestibility of most AAs and total AAs was independent of their respective dietary protein levels. Collectively, the 15N-leucine single-injection method is appropriate for determining EAALs and the true digestibility of AAs in poultry fed varying levels of protein-containing ingredients.

Comparative Study of Endogenous Ileal Amino Acid Flow and Digestive Physiology to Nitrogen-Free Diets with Differing Ratios of Dextrose to Corn Starch in Broiler Chickens

“…Some reports in broiler chickens identi ed that total IEAAs were signi cantly higher when dextrose was used as a sole source of energy in NFD compared with corn starch (17544 vs. 12779 mg/kg of dry matter intake) 9 . Similar ndings were reported in broilers study, wherein the IEAAs loss in NFD containing only glucose was signi cantly higher than that in NFD containing only corn starch (11080 vs. 6038 mg/kg of dry matter intake) 10 .These studies clearly indicated the in uence of the varying ratios of corn starch and dextrose on IEAAs losses, thereby affecting the accuracy of the SID. Arguably, these studies did not present the possible explanation for the difference in IEAAs loss brought in by the ratio of starch to dextrose.…”

Comparison of endogenous amino acid losses in broilers when offered nitrogen-free diets with differing ratios of dextrose to corn starch

“…There are many methods to determine the IEAAs losses in broiler chickens, such as the regression method, the enzymatically hydrolyzed casein method, the NFD method, and the 15 N-leucine single-injection method 7 , 13 . Among these various methods, the NFD method is most widely used for its simplicity, convenience, and low cost.…”

High amylose to amylopectin ratios in nitrogen-free diets decrease the ileal endogenous amino acid losses of broiler chickens

“…In broiler chickens, several approaches have been used to determine IEAA losses ( Golian et al., 2008 ; Hu et al., 2017 ), but the nitrogen-free diet (NFD) method is currently considered the best strategy among available techniques because of its simplicity, convenience, and cost-effectiveness ( Ravindran, 2021 ). Mostly NFD consist of corn starch and dextrose or sucrose as the main components.…”