Olfactory cue mediated neonatal recognition in sheep, Ovis aries.

The strong bond between ewe and lamb formed shortly after parturition is an important factor in lamb survival. Evidence exists that a ewe can distinguish her lamb by its unique smell, but the constituents of such a putative olfactory cue have not yet been identified. We have now identified 133 volatile organic compounds associated with the wool of Döhne Merino lambs that we presume may be involved in neonatal recognition. Quantitative analysis and comparison of odor profiles of the twins of 16 ewes (9.69% sample group) of a flock of 165 twin-bearing ewes revealed that the wool volatiles of twins are qualitatively and quantitatively similar, but differ from those of other twins or non-twin lambs in the flock. The 88 constituents present in at least 20% of the analyzed wool samples were considered as variables for multivariate analysis. A P-value < 0.001 was calculated, indicating that the pairing of twins according to the qualitative and quantitative composition of the wool was significant. Bioassays carried out during the lambing seasons of 2009 and 2010 confirmed the previously established role of lamb odor in ewe-lamb recognition. However, when alien lambs were dressed in jackets sprayed with synthetic mixtures formulated to match the chemical composition of the effluvia of the ewes' own lambs, ewes rejected the aliens. This is possibly because the VOCs were not released in quantitative ratios sufficiently accurate to emulate the odor of the ewes' own lambs.