Abstract

MEJIA VILLANUEVA, Octavio et al. Progesterone promotes foetal growth in a restricted interspecies gestation (Ovis canadensis × Ovis aries). Veterinaria México OA [online]. 2018, vol.5, n.3. ISSN 2448-6760.  https://doi.org/10.22201/fmvz.24486760e.2018.3.507.

Gestations between bighorn (Ovis canadensis) and domestic sheep (O. aries) can be considered for ex situ conservation of bighorn. In the first experiment, domestic sheep were inseminated with bighorn or domestic semen. Bighorn inseminated sheep showed lower fertility than domestic inseminated sheep (40% vs. 65%, p = 0.11). Bighorn inseminated sheep had longer gestation periods (152.13 days vs. 146.54 days, p < 0.001) and lower progesterone levels during the last third. Hybrid lambs weighed less than domestic lambs (2.46 kg vs. 5.10 kg, p < 0.001). Their placentas were not as long (48.67 cm vs. 72.17 cm, p < 0.001), were less wide (17.83 cm vs. 23.83 cm, p < 0.001), and the weight of cotyledons was lower (1.50 g vs. 3.20 g, p < 0.001). In the second experiment, hybrid embryos (O. canadensis × O. aries) were transferred into domestic recipients, and pregnant ewes were divided into the treated group, which had a progesterone daily dose of 25 mg from weeks 7 to 20, and the non treated group. Gestation in domestic sheep that received one hybrid embryo and progesterone reached 152.60 days, which was similar to the 153.33 days (p = 0.51) in the non treated sheep. Hybrid offspring of the group treated with progesterone were heavier, 3.41 kg, than the control, 2.21 kg (p < 0.001), and their placentas were longer (71.20 vs. 50.83 cm, p = 0.002). Although progesterone levels were lower in domestic females inseminated with bighorn and in the recipients of hybrid embryos, it is possible to establish pregnancies between both species and the birth of viable offspring. The administration of progesterone during gestation increases the length of the placenta and promotes higher birth weights of hybrids.

Keywords : foetal growth; progesterone; Ovis canadensis; Ovis aries; interspecies gestation.