Abstract
Progesterone promotes foetal growth in a restricted interspecies gestation (Ovis canadensis × Ovis aries). Veterinaria México OA. 2018;5(3).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.Figure 1. Progesterone (ng/mL) in interspecies gestations (O. c. mexicana × O. aries, n = 6) and intraspecies gestations (O. aries × O. aries, n = 6).*Statistically different values (p < 0.01).
Highlights
Bighorn sheep is one of 14 species of Mexican fauna considered a priority under special protection status by NOM-059-ECOL-2010,1,2 and only the bighorn sheep of México is still in Appendix II of the Convention on International Trade of Wild Fauna and Flora Endangered Species.[3]
Domestic sheep inseminated with frozen bighorn semen had reduced fertility, 40% (8/20), when compared to those inseminated with domestic semen, 65% (13/20), (x2(1) = 2.50, p = 0.11)
Progesterone levels were lower during the final third of interspecies gestations (O. c. mexicana × O. aries) when compared to the levels determined from domestic sheep gestations (O. aries × O. aries), (F(33, 170) = 9.35, p < 0.001, partial η2 = 0.64)
Summary
Bighorn sheep is one of 14 species of Mexican fauna considered a priority under special protection status by NOM-059-ECOL-2010,1,2 and only the bighorn sheep of México is still in Appendix II of the Convention on International Trade of Wild Fauna and Flora Endangered Species.[3]. Assisted reproduction techniques in wild animal practice as a tool for conservation have been widely discussed by several authors,[10,11] but there has been little progress in terms of the possible value of interspecies gestations. This is because there are important knowledge voids on the phylogenetic closeness, differences in oestrous cycle and gestation length, differences in placenta formation, and in the immunological gestation that have sparked conflicts.[12]. This work sought to confirm if the production of hybrids is viable, despite the phylogenetic distance between bighorn and domestic sheep, and if the administering of progesterone throughout these gestations could favour placental development and promote foetal growth
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