Agroecology 2 min

Variation of ewe olfactory secretome during a ram effect

Exposure of ewes in anoestrus to a sexually active male in a male effect protocol reactivates a O-GlcNAcylation of nasal mucus proteins that exists only in cycled ewes. These modified proteins would allow the female to better detect the male odours responsible for the resumption of their cyclicity.

Published on 24 February 2023

illustration Variation of ewe olfactory secretome during a ram effect

Under temperate latitudes, reproduction in Ovis aries displays a marked seasonality, governed by the photoperiod. In natural conditions, the transition between sexual rest and sexual activity in both sexes is induced by the decrease of daylight. Meanwhile, specific odors emitted by a sexually active male are able to reactivate the gonadotropic axis of anovulatory ewes.

This physiological effect is called a “male effect”, precisely a ram effect in the ovine species. We have previously shown that the secreted proteins, namely Olfactory Binding Proteins (OBP), contained in the nasal mucus constitute the olfactory secretome (OS), the composition of which is determined by the status of oestrus cycle of females and differs between sexual rest and sexual activity periods. The objective of this study was to test the hypothesis that exposure to a sexually active male can also modify the composition of ewes olfactory secretome during a male effect, as well as hormones produced by the reactivation of the oestrus cycle in sexual activity period under natural conditions.

We have set up a new non-invasive protocol of nasal mucus sampling and collected it from 12 ewes at different times during a ram effect. We analyzed the composition of their olfactory secretome by proteomics, mainly SDS-PAGE and MALDI-TOF mass spectrometry. As post-translational modifications of OBPs were a hallmark of ewes’ sexual activity period, we were looking for glycosylation by western-blot and mass spectrometry.

The efficiency of male effect was low in stimulated ewes as only 3 females displayed elevated progesterone levels in their blood. Besides, half of control ewes (non-stimulated ones) were cycled. We noticed a common OS profile in ewes in anoestrus, versus OS of cycled ones. A very clear and important result was the apparition of O-GlcNAcylation, previously detected only in sexual activity, after only 30 min of introducing a male into the flock.

This exploratory study paves the way for further experiments with a larger flock to confirm and reinforce these results, and for eventually exploiting the nasal mucus as an indicator of females’ receptivity to male odors.



scientific contacts

Matthieu Keller Reproductive Physiology and Behavior Unit

Timothée Zidat Reproductive Physiology and Behavior



Learn more


When genetic selection preserves traditions

ARTICLE BY EXPLORER - What would be the Pyrenean cultures and in particular those of the Basque Country and Bearn without sheep? An integral part of traditional agricultural life, they have shaped the landscape for generations on both sides of the border. In 2021, the entire livestock sector, along with researchers, is taking action to preserve these indigenous breeds: the Latxa on the Spanish side and the Manech and Basco-Béarnaise on the French side. In this way, the ARDI project was born, which works for extensive agriculture and optimizes ancestral practices through genetic selection. Meeting with the "Basque, Navarrese and Spanish" agronomist Andrés Legarra, research director at INRAE Occitanie-Toulouse, from the GenPhySE laboratory.

14 June 2021