PURPOSE: To provide the titled agent comprising L-dopa (derivative) and a specific amino acid.

CONSTITUTION: An animal breeding promoting agent comprising (A) L-dopa or its derivative, e.g. 3,4-dipivalyloxy-N-(1-methyl-2-acetylvinyl)-L-phenylalanine-pival- yloxymethyl ester, (B) pref. an L-dopa-metabolism inhibitor, e.g. L-α-hydrozino-3,4 -dihudroxy-α-methyl-β-phenylpropionic acid, and (C) an amino acid selected from L-arginine, L-ornithine, L-lysine, D-phenylalanine, L-glutamic acid, and γ-aminobutyric acid. The amount of the L-dopa per dose is 0.2W50mg/kg, and the ratios of the L-dopa-metabolism inhibitor and the amino acid to the L-dopa are 0.01W10, respectively.