Interspecies pregnancy of Spanish ibex (Capra pyrenaica) fetus in domestic goat (Capra hircus) recipients induces abnormally high plasmatic levels of pregnancy-associated glycoprotein

Interspecies embryo transfer could be a valuable tool in preservation programs of endangered species. In this work the results of both interspecific-monospecific (ibex-in-goat) and interspecific-bispecific (mixed-species; ibex+goat-in-goat) embryo transfers in the capra genus are reported. The aim of this work was to compare the PAG plasmatic profiles occurring in these interspecific gestations to those encountered in normal (i.e. intraspecies) pregnancies of Spanish ibex and domestic goat. Spanish Ibex females were superovulated with 9 mg NIADDK-oFSH-17 and embryos were surgically collected 5.5 d after estrus. Two embryos were transferred per recipient. Domestic goat recipients were previously mated either to vasectomized domestic bucks (n=17 females; interspecific-monospecific gestations) or to fertile ones (n=9 females; interspecific-bispecific gestations). Intraspecific pregnancies were obtained by natural mating between males and females of the same species (Spanish ibex: n=6; domestic goat: n=1). Pregnancy rate diagnosed by progesterone was low in both interspecific-monospecific (7/17) and interspecific-bispecific (3/9) transfers. None of the monospecific (0/7) and 2 (2/3) of the bispecific established pregnancies developed to term. Ibex-in-ibex PAG profile showed 2 similar peaks of 60 to 70 ng/mL on Days 34 and 153 of pregnancy, while goat-in-goat had the maximum value (60 to 70 ng/mL) at Day 50, decreasing slightly afterwards until parturition. Mixed-species gestations (ibex+goat in goat) showed a first peak of 500 to 1000 ng/mL on Day 70 and a second one (200 to 500 ng/mL) on Day 140 of pregnancy. Four ibex-in-goat gestations that terminated with the expulsion of dead fetuses at Days 110 to 170 had their maximum PAG values (100 to 700 ng/mL) on Days 60 to 90. We conclude that it is possible to achieve pregnancies after transfer of ibex embryos into domestic goats, but this requires a great change of the PAG profiles, which increase significantly. Live ibex kids can be produced when embryos from both species share the uterus. This is the first report of successful interspecific pregnancies in the capra genus.