Manipulating odor cues facilitates add-on fostering in sheep

Manipulating the odor of a ewe's own and alien lambs has been used to facilitate fostering a second lamb on ewes with a single offspring (add-on fostering). Previous research has demonstrated that familiar odor cues must be present on the own and alien young to achieve successful and rapid adoptions. Familiar odors may consist of natural own-lamb odors or artificial odors previously applied to the lambs involved. In the present study (Exp. 1), an artificial odorant (neatsfoot oil) was applied to the own and alien lambs shortly after birth to establish a common familiar odor. Acceptance tests were conducted daily over a 72 h period. In Exp. 2, neatsfoot oil was again used as a common artificial odorant to facilitate add-on fostering, but, in addition, the natural odors of own and alien lambs were transposed by exchanging cloth stockinette jackets worn by the lambs. In Exp. 1, 9 of 18 ewes (50%) met the criteria for accepting their own and alien lambs within 72 h. Seven of these nine ewes (78%) accepted the alien lamb immediately. In Exp. 2, 24 of 30 ewes (80%) accepted their own and alien young, and 20 of the 24 acceptances (83%) were immediate. We conclude that add-on fostering may be limited only by our inability to properly match familiar-odor cues on own and alien lambs.