The male effect in ungulates: agronomic applications and neuroendocrine mechanisms. – MALE-EFFECT

Behavior, hormonal assay (progesterone, LH), echography.

So far, we have performed task 2 and showed that bucks are able to induce an efficient male effect on 3 successive groups of females. Results, which have been partly obtained in 2011 have been published (Bedos et al., Physiology & Behavior, 2012). We have also performed tasks 1 and 3. Task 1 was dedicated to explore whether only 1h of daily contact with sexually active buck is sufficient to induce a male effect. We have explore the physiological mechanisms involved in task 3 and showed that permanent vs intermittent contact qith the male induces ovulation through different mechanisms. While permanent contact with the male induce ovulation within the 2-3 days of contact, ovulation seems to occur later when females are in intermittent contact with the male (ovulations after day 5, progesterone and LH assays).

From September, we will start tasks 4 (brain imaging) and 5 (activation of kisspeptin cells). These 2 tasks will be more time consuming and will probably conitnue until the end of the project (task 4) or during the next 18 months (task 5). Given the good advance of the project, we intend to add a supplementary experiment depending on the funding available.

BEDOS M., VELAZQUEZ H., FITZ-RODRIGUEZ G., FLORES J.A., HERNANDEZ H., DUARTE G.D., FERNANDEZ I.D., MUNOZ-GUTIERREZ M., RETANA-MARQUEZ S., KELLER M. & DELGADILLO J.A. (2012). Sexually active bucks are able to stimulate three successive groups of females per day with a 4-hour period of contact. Physiology & Behavior, 106, 2, 259-263.

Ungulates (sheep, goats...) have a seasonal breeding characterised by a period of sexual activity (short-dayd period, november-april) followed by a period of sexual rest (or anestrus period, long-days period, may-october). During the season of sexual rest, females are reproductively quiescents and have therefore no ovarian cycle nor ovulation. However, if during this period they are exposed to a male, they will undergo a complete reactivation of their gonadotropic axis measured through LH pulsatility (short-term response) leading to an ovulation (long-term response). This effect is called the "male effect" and is an attractive technique to control ungulate reproduction in a context of clean, green and ethical farm productions development. Indeed, using the male effect is an alternative to the usual administration of exogenous hormones which can act as endocrine disruptors once released in the environment. In addition, this technique is also a low-cost solution to have reproduction during the anestrus season where animal products derived from lambing/kidding (meat, milk...) are present in a limited amount. However, the use of the male effect under breeding conditions is still limited. In this context, our laboratories (Physiologie de la Reproduction et des Comportements, France, Universidad Autonoma Agragrio Antonio Narro, Mexique et Universidad Nacional Autonoma de Mexico) have recently shown (Bedos et al., Hormones & Behavior, accepté) that 4h of daily contact with a sexually active male during 15 days (instead of a permanent contact) is sufficient to induce an efficient male effect, that is a to induce 100% of gestation in female goats. This result opens new perspectives for breeding applications as well as for the neuroendocrine mechanisms involved.This projects is thus dedicated to define the optimal contact parameters (duration of daily contact, number of famels that a male can stimulate...) to perform an efficient male effect in a maximal number of females. In a second part, we want to compare the neuroendocrine mechanisms inducing a whole reactivation of the gonadotropic axis depending on the contact duration (intermittent vs permanent). In this context, we will use different approaches (assay of LH pulsatility, measure of brain activation thourgh functional brain imaging, and neurochemical characterization of neuronal populations by immunocytochemistry).