Oestrus synchronization in postpartum autumn-lambing ewes: effect of postpartum time, parity, and early weaning

• Autores: R. Ungerfeld, F. Sánchez Dávila
• Localización: Spanish journal of agricultural research, ISSN-e 2171-9292, ISSN 1695-971X, Vol. 10, Nº. 1, 2012, págs. 62-68
• Idioma: inglés
• Enlaces
  • Texto completo (pdf)
• Resumen

  • Three experiments were performed to determine the effect of postpartum time interval, the influence of parity (primimarous vs multiparous), and lamb weaning on the response of postpartum ewes to oestrus synchronization/induction treatments during the breeding season. In the Experiment 1 ewes were treated with an 8-days medroxyprogesterone priming and 350 IU of eCG, starting 14-18 (EPP), 24-30 (MPP), or 42-48 (LPP) days postpartum. More EPP than LPP ewes were marked by rams (p < 0.05), but conception rate was similar. In Experiment 2, 36 primiparous and 47 multiparous ewes that lambed during autumn received a 12-days medroxyprogesterone treatment followed by the introduction of rams. Ewes that came into oestrus, and that had a corpus luteum on Day 5 was greater in multiparous than in primiparous ewes (p = 0.04 and p = 0.03 respectively). Pregnancy rates on Day 35 and on Day 90 were similar. Experiment 3 was conducted with 26 ewes that remained with their lambs suckling during all the experiment, and 26 that were weaned ~27 days after birth, 3 days before the introduction of the rams. There were no differences on the percentage of ewes that came into oestrus, or the conception rate. We concluded that in postpartum ewes that had lambed during the breeding season: (1) is possible to induce fertile oestrus during early postpartum; (2) the early response was greater in multiparous rather than in primiparous ewes, although after a 35 d-breeding period differences disappeared and (3) weaning lambs early before stimulation did not improve the response.