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Vet. Sci. 2017, 4(1), 4; doi:10.3390/vetsci4010004

Exposure to Photoperiod-Melatonin-Induced, Sexually-Activated Rams after Weaning Advances the Resumption of Sexual Activity in Post-Partum Mediterranean Ewes Lambing in January

1
Instituto Universitario de Investigación en Ciencias Ambientales (IUCA), Departamento de Producción Animal y Ciencia de los Alimentos, Universidad de Zaragoza, Miguel Servet, 177, Zaragoza 50013, Spain
2
Physiologie de la Reproduction et des Comportements, Institut National de la Recherche Agronomique, Centre National De La Recherche Scientifique (INRA, CNRS), Université de Tours, Agreenium, Nouzilly 37380, France
3
Departamento de Construcción y Agronomía, Facultad de Ciencias Agrarias y Ambientales, Filiberto Villalobos, Salamanca 37007, Spain
4
Centro de Investigación en Reproducción Caprina, Universidad Autónoma Agraria Antonio Narro, Periférico Raúl López Sánchez y Carretera a Sante Fe, C.P. 27054, Torreón, Coahuila, Mexico
*
Author to whom correspondence should be addressed.
Academic Editor: Patrick Butaye
Received: 12 November 2016 / Revised: 19 December 2016 / Accepted: 18 January 2017 / Published: 21 January 2017
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Abstract

This study was aimed to determine whether the presence of sexually stimulated rams by photoperiodic and melatonin treatments can advance the resumption of post-partum sexual activity in Mediterranean ewes lambing in January and weaned at the end of the breeding season at 41°N, in March. Rams were exposed to two months of long days (16 h light/day) and given three melatonin implants at the end of the long days (sexually-activated rams; SAR). Control rams (CR) were exposed to the natural photoperiod. Thirty-six ewes weaned on 25 February were assigned to one of two groups. From 1 March to 30 June, one group was housed with four SAR males (SAR-treated; n = 18), and the other group (CR-treated; n = 18) was housed with four unstimulated rams. Ovulation was assessed once per week based on plasma progesterone concentrations. Estrus was monitored daily by marks left on ewes by rams’ harnesses. SAR-treated ewes had a shorter (p < 0.01) weaning–first estrus interval than CR-treated ewes (61 ± 17 days vs. 102 ± 47 days; mean date of first estrus after weaning on April 26 and June 6, respectively). The proportion of the ewes ovulating in April or May was higher (p < 0.05) in the SAR-treated group than in the CR-treated group. SAR-treated ewes resumed estrous activity sooner than CR-treated ewes such that, in April, May, and June, the proportion of females that exhibited estrus was higher (p < 0.01) in the SAR-treated group (72%, 89%, and 100%, respectively) than in the CR-treated group (17%, 44%, and 61%, respectively). In conclusion, the introduction at weaning of sexually activated rams advanced the resumption of estrous activity in ewes in spring. The practical implications of this work could be important in ewes adapted for intensive production and accelerated lambing systems. View Full-Text
Keywords: ram; photoperiod treatment; melatonin; anestrus ram; photoperiod treatment; melatonin; anestrus
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Abecia, J.A.; Chemineau, P.; Gómez, A.; Palacios, C.; Keller, M.; Delgadillo, J.A. Exposure to Photoperiod-Melatonin-Induced, Sexually-Activated Rams after Weaning Advances the Resumption of Sexual Activity in Post-Partum Mediterranean Ewes Lambing in January. Vet. Sci. 2017, 4, 4.

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