Comparison of two oestrus synchronization protocols with progestogens and eCG (equine chorionic gonadotropin) in Corriedale ewes under high altitude conditions

Luque-Mamani N.; Suaña-Yana A.; Macedo-Sucari R.; Pérez-Durand M.; Perez-Guerra U.H. · Revista de Investigaciones Veterinarias del Peru (2025) · DOI: 10.15381/rivep.v36i1.30204

Resumen

The aim of this study was to compare two oestrus synchronization protocols with progestogens and eCG in Corriedale ewes under high altitude conditions. In total, 50 ewes with a body condition score (BCS) between 2.5 and 3.0 and two 4-year-old Corriedale rams with BCS 2.5 were used. In both protocols, vaginal sponges with medroxyprogesterone were used for 14 days. In the protocol for treatment I (TI: 25 ewes) eCG (equine chorionic gonadotropin) was applied on day 12 and in treatment II (T2: 25 ewes) eCG was applied on the day of sponge extraction (day 14). The characteristics of the vaginal mucosa were evaluated prior to artificial insemination (AI). Semen was collected by artificial vagina and diluted with Andromed®. AI was performed on day 16. Ultrasonographic evaluation was used to determine the diameter of the uterine horns, the diameter of the dominant follicles (DF), and the growth rate of the uterine horns and DF. A difference was observed in the diameters of the right and left uterine horns in favour of T1 in relation to T2 on day 16, as well as in the growth rates (T1: 0.15 to 0.16; T2: 0.05 and 0.07 mm/day) and DF (T1: 1.54; T2: 0.15 mm/day). The comparison between pregnant and non-pregnant females showed a statistical difference, being greater (diameter of uterine horns and DF) in the pregnant group. Logistic regression showed only statistical difference in pregnancy between treatments, however, the pregnancy rate for T1 was 56% and for T2 48% (p>0.05). In conclusion, the application of eCG 96 hours before AI (T1) produces greater diameters of uterine horns and dominant follicles and higher growth rates that could be related to a higher pregnancy rate compared to T2. © Los autores.

Instituciones: Universidad Nacional de San Antonio Abad del Cusco; Universidad Nacional del Altiplano