The invention relates to a ligand of a luteinizing hormone (LH), characterized in that it comprises the paratope of an ovine anti-LH antibody of which the variable domain of the heavy chain contains the following CDRs: —VH-CDR1, defined by the sequence GYTFTNYW (SEQ ID NO: 13)； —VH-CDR2, defined by the sequence IYPGGGYT (SEQ ID NO: 14)； —VH-CDR3, defined by the sequence ARTPLYGSSYGGFAY (SEQ ID NO: 15)； and the variable domain of the light chain contains the following CDRs: —VL-CDR1, defined by the sequence QGISNY (SEQ ID NO: 16)； —VL-CDR2, defined by the sequence YTS； —VL-CDR3, defined by the sequence QQYSKLPWT (SEQ ID NO: 17). The invention also relates to a ligand-gonadotrophin (LH, hCG, FSH) complex. The ligand or the complex according to the invention can be used to induce ovulation in a female mammal.
