Evaluation of compound-specific N isotopes analysis in key amino acids to predict feed efficiency in growing lambs

Cantalapiedra-Hijar, Gonzalo; Prache, Sophie; Tea, Illa; Faure, Sandrine; Chantelauze, Céline; Ortigues Marty, Isabelle

Evaluation of compound-specific N isotopes analysis in key amino acids to predict feed efficiency in growing lambs

2016

AbstractTo measure feed efficiency in growing ruminants we proposed an improved isotopic method basedon natural 15N abundance (δ15N). Individual feed conversion efficiency (FCE) was measured for 75days in 48 growing lambs fed diets based on Lucerne and supplemented with either a high or lowamount of barley. The δ15N analysis was conducted in bulk N from feed ingredients and animalmuscle to calculate the isotopic N fractionation (Δ15Nanimal-diet, δ15Nanimal - δ15Ndiet) and by compoundspecificisotopic analysis on amino acids to obtain the δ15N of transaminating amino acids(δ15NTAAs). Isotopic values obtained with both approaches (Δ15Nanimal-diet and δ15NTAAs) were regressedagainst the observed FCE. We show an improvement in FCE prediction when analysis of 15N naturalabundances is conducted on transaminating amino acids rather than on bulk N.

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