Light-induced sexually active rams provoke LH preovulatory surges and enhances LH concentrations in ewes after progestagen treatment

José A Abecia; Matthieu Keller; Philippe Chemineau; José A Delgadillo

doi:10.1016/j.heliyon.2020.e03529

Light-induced sexually active rams provoke LH preovulatory surges and enhances LH concentrations in ewes after progestagen treatment

Heliyon. 2020 Mar 5;6(3):e03529. doi: 10.1016/j.heliyon.2020.e03529. eCollection 2020 Mar.

Authors

José A Abecia¹, Matthieu Keller², Philippe Chemineau², José A Delgadillo³

Affiliations

¹ IUCA. Departamento de Producción Animal y Ciencia de los Alimentos. Universidad de Zaragoza, Zaragoza, Spain.
² Physiologie de la Reproduction et des Comportements, UMR INRA, CNRS, Université de Tours, IFCE, Agreenium, Nouzilly, France.
³ Centro de Investigación en Reproducción Caprina, Universidad Autónoma Agraria Antonio Narro, Torreón, Coahuila, Mexico.

Abstract

The effect of the introduction of sexually active rams in spring on LH secretion in ewes after progestagen treatment has been studied. Two rams were induced into a sexually active state by exposure to 2 months of long days (16 h of light/d) from 1 January (SAR), and another 2 rams were exposed to the natural photoperiod, so that they were not sexually activated in spring (control; C). At the end of the long-day period, rams were returned to natural photoperiod conditions. Fifteen ewes synchronized in estrus by intravaginal sponges were assigned to three groups at sponge withdrawal (hour 0): SAR (n = 5), exposed to SAR rams; C (n = 5), exposed to C rams, and ISO (n = 5), kept isolated from rams. Twenty-four hours after pessary removal (hour 0), rams were introduced into the SAR and C groups. Three SAR ewes presented preovulatory LH surges; the proportion was significantly (P < 0.05) higher in this group (3/5) than in the others (C: 0/5, ISO: 0/5). SAR introduction induced a more marked (P < 0.05) increase in mean LH plasma concentrations (before rams: 1.34 ± 0.19; after rams: 6.94 ± 2.66 ng/ml) than C (before: 0.96 ± 0.29; after: 3.60 ± 1.44) or ISO (before: 1.26 ± 0.42; after: 2.14 ± 1.36) groups, and significantly (P < 0.05) higher plasma LH levels after ram introduction. In conclusion, only light-treated sexually activated rams induced LH preovulatory surges in ewes in the seasonal anestrus, when ewes are synchronized with progestagen treatment in the absence of eCG.

Keywords: Agricultural science; Anestrus; Animal breeding; Animal science; Endocrinology; LH; Physiology; Ram; Reproductive hormone; Sexual behavior; Sheep; Veterinary sciences.