title: Presence of photoperiod-melatonin-induced, sexually-activated rams in spring advances puberty in autumn-born ewe lambs.
abstract: The objective of this study was to determine the effect of sexually activated (by specific photoperiodic treatments) vasectomized rams on the onset of puberty in autumn-born ewe lambs in spring. Photoperiodic-treated rams were assigned to one of three groups, which were sequentially exposed to two months of long days (16h light/d) and given three melatonin implants at the end of the long days (sexually-activated-rams; SAR): SAR1 (n=5; 1 December-31 January), SAR2 (n=5; 1 Jan-28 February), and SAR3 (n=5; 1 February-31 March). Control rams (CR; n=4) were exposed to the natural photoperiod. On 1 March, 50 ewe lambs born in September were assigned to the SAR rams (SAR-treated; n=25) or the CR rams (CR-treated; n=25). SAR-treated ewe lambs were housed with SAR1 rams from 1 March. SAR2 rams replaced SAR1 rams (14 April), which were replaced by SAR3 rams (22 May) until 30 June. CR-treated ewe lambs were housed with the unstimulated rams. Ovulation was identified by weekly plasma progesterone concentrations and estrous behavior, as indicated by colored rumps. A greater proportion of SAR than CR ewe lambs ovulated in April (52% vs. 0%) and May (68% vs. 0%) (P<0.0001), and were in estrus in May (64% vs. 0%) and June (92% vs. 24%) (P<0.0001). The presence of SAR rams reduced (P<0.0001) mean (±SD) age (d) at first ovulation and estrus (235±28 [7 May] and 257±24 [29 May], respectively), compared to that of CR-treated ewe lambs (277±5 [18 June] and 302±16 [14 July], respectively). In conclusion, the presence of photoperiod-melatonin-induced, sexually activated rams in spring, advanced puberty in autumn-born ewe lambs. Using this technique might provide an effective and sustainable means of increasing the productive life of ewes, while avoiding the use of hormonal treatments.
authors.affiliation: IUCA, Departamento de Producción Animal y Ciencia de los Alimentos, Universidad de Zaragoza, Miguel Servet, 177, 50013 Zaragoza, Spain. Electronic address: alf@unizar.es.
authors.forename: J A
authors.initials: JA
authors.lastname: Abecia
authors.affiliation: Physiologie de la Reproduction et des Comportements, UMR INRA, CNRS, Université de Tours, IFCE, Agreenium, 37380 Nouzilly, France.
authors.forename: P
authors.initials: P
authors.lastname: Chemineau
authors.affiliation: IUCA, Departamento de Producción Animal y Ciencia de los Alimentos, Universidad de Zaragoza, Miguel Servet, 177, 50013 Zaragoza, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Gómez
authors.affiliation: Physiologie de la Reproduction et des Comportements, UMR INRA, CNRS, Université de Tours, IFCE, Agreenium, 37380 Nouzilly, France.
authors.forename: M
authors.initials: M
authors.lastname: Keller
authors.affiliation: IUCA, Departamento de Producción Animal y Ciencia de los Alimentos, Universidad de Zaragoza, Miguel Servet, 177, 50013 Zaragoza, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Forcada
authors.affiliation: 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.
authors.forename: J A
authors.initials: JA
authors.lastname: Delgadillo
mesh_terms: D000375:Aging; D000818:Animals; D004343:Drug Implants; D030762:Estrous Cycle / Q000502:physiology; D005260:Female; D008297:Male; D008550:Melatonin / Q000008:administration & dosage / Q000494:pharmacology*; D017440:Photoperiod; D012741:Sexual Maturation / Q000187:drug effects* / Q000502:physiology; D012756:Sheep / Q000502:physiology*
chemical_list: D004343:Drug Implants; D008550:Melatonin
keywords: Ewe lambs; Melatonin implants; Photoperiod treatment; Puberty; Ram