Cristina Castaño

Background: Immunocontraception is a population management strategy based on vaccines that induce an immune response against reproductive targets such as GnRH. Objectives: This study aimed to investigate spermatogenic activity in adult baboons and adult dwarf bucks subject to repeated immunisation against GnRH for extended periods. Methods: In Experiment 1, histological findings in untreated dwarf bucks (CONTROL‐1) ( n =  10) were compared with those found in males repeatedly immunised against GnRH (Improvac) during 5 years (RI‐1; n =  15). In Experiment 2, one group of baboons received immunocontraceptive treatment against GnRH during 5–10 years until death (RI‑2; n =  6). The second group received the same treatment for 10 years before discontinuation, with the interval between treatment withdrawal and death ranging from 10 to 27 months (RI‑2+S; n =  19). As in Experiment 1, testicular tissue was collected post‐mortem and processed histologically. Results: In both species, the testicular tissue of animals treated with repeated immunisation against GnRH showed an absence of active spermatogenesis. The mean seminiferous tubule diameter in bucks was smaller in the RI‐1 group than in the CONTROL‐1 group (108.69 ± 13.17 µm vs. 187.35 ± 14.38 µm; p  < 0.05). In baboons, morphometric analysis showed similar seminiferous tubule diameters in the RI‐2 (82.63 ± 4.47 µm) and RI‐2+S (79.23 ± 5.89 µm) groups. Conclusions: In bucks and in more than 70% of baboons, the severity of degenerative changes in the germinal epithelium suggests that long‐term repeated immunisation against GnRH may lead to irreversible infertility.

The present study compares two protocols for the cryopreservation of chicken semen. Both protocols had an initial low cooling rate in the first step, followed by higher cooling rates around ice nucleation (Protocol 1) or following the dissipation of the latent heat of fusion (Protocol 2) in the second step. Semen ejaculates obtained from 12 roosters were diluted with Rootex with 6% dimethylformamide and frozen following either Protocol 1 (from +5°C to −10°C at 5°C/min and from −10°C to −130°C at 60°C/min) or Protocol 2 (from +5°C to −35°C at 7°C/min and from −35°C to −140°C at 60°C/min). Compared with fresh semen, following both protocols, cryopreservation resulted in reduced post‐thaw sperm quality (p < .001). Post‐thaw percentage of sperm with an intact plasma membrane was greater using Protocol 2 than Protocol 1 (p < .05). The results suggest that high cooling rates around the time of ice nucleation are not recommendable.

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).