Characterization of amniotic fluid of Dohne Merino ewes (Ovis aries) and its possible role in neonatal recognition

Amniotic fluid (AF) was investigated as a possible source of the neonatal recognition cue that plays a crucial role in ewe–lamb bonding in sheep. A total of 70 of the 133 volatile organic compounds (VOCs), previously identified in the cranial wool of neonatal Dohne Merino lambs, was also identified in AF collected individually from neonatal twins. As in the case of the wool of neonatal lambs, the VOC profiles (GC-MS) of the AF of twins were remarkably similar. However, the VOC profiles of the AF differed from that of the wool VOCs of the same lambs. The VOCs that best represent the total variance in the AF and wool of neonatal lambs were not identified as ligands of the AF proteins. These observations suggest that it is unlikely that the neonatal recognition cue of sheep could be a maternal label derived from the AF in which a lamb is born, and that the neonatal recognition cue is probably produced by the lamb. Taking cognizance of the temporal changes that take place in the quantitative composition of the cranial wool VOCs, we hypothesize that components of the neonatal recognition cue are already produced by the lamb well before its birth and that the quantitative composition in which these volatiles are released into the AF does not correspond to the composition of the recognition cue of the lamb at its birth. When grooming the newborn lamb, its mother removes AF containing incorrect chemical information from her lamb’s body and this affords her enough time to learn its personal recognition cue.