Un excès de leucine aggrave l’effet d’une carence en valine chez le porcelet

The branched‐chain amino acids (BCAA: valine (Val), leucine (Leu), isoleucine) are considered to be among the next‐limiting amino acids for growth in piglets. In earlier studies, we estimated the standardized ileal digestible (SID) Val:Lys requirement at 70%. Because the BCAA partially share a common route of catabolism, the supply of one BCAA may affect the availability of the other BCAA. Two experiments were conducted to determine the response of 6‐week‐old piglets to the Val supply in relation to the excess of Leu. In experiment 1, the interaction between Val and Leu was studied in a 2x2 factorial design (60 and 70% SID Val:Lys, and 111 and 166% SID Leu:Lys). Daily gain decreased and feed conversion ratio increased by 30% and 23% respectively in piglets receiving 60% SID Val:Lys compared with those receiving 70% SID Val:Lys and was lowest in piglets receiving the diet with a low Val and high Leu content. To further evaluate the interaction between Val and Leu, a dose‐response study was carried out in which the response to Val supply was studied in combination with a high Leu content (165% SID Leu:Lys). Using a curvilinear‐plateau model, the average SID Val:Lys requirement was 72%. However, a low Val supply (60% SID Val:Lys) reduced performance by 13 to 38%, which was much greater than what we observed in earlier studies. In conclusion, a large supply of Leu does not affect the Val requirement per se, but may aggravate the consequences of a Val deficiency