Factors Affecting Pregnancy in Ewes Subjected to Estrus Synchronization and Artificial Insemination Under Field and High-Altitude Conditions

Perez-Guerra U.H.; Angel E.-A.; Peña-Hancco R.R.; Manrique-Quispe Y.P.; Natalio L.-M.; Condori-Morales R.M.; Halley R.-H.F.; Amadeus D.-C.E.; Pérez-Durand M.G. · Journal of Animal Health and Production (2025) · DOI: 10.17582/journal.jahp/2025/13.4.1067.1072

Resumen

The objective of this study was to identify factors influencing pregnancy rates in artificial insemination (AI) programs for ewe lambs subjected to estrus synchronization protocols under field and high-altitude conditions. The study was conducted in the Llalli district, Melgar province, involving 120 ewe lambs aged 2 to 4 years with body condition scores between 2.5 and 3.5, all managed by local producers under field conditions. Two estrus synchronization protocols were applied using intravaginal progestogen sponges: 14 days (TI, n=60) and 12 days (TII, n=60). Upon sponge removal, 400 IU of equine chorionic gonadotropin (eCG) was administered intramuscularly, and AI was performed 56 hours later using fresh diluted semen from two proven fertile rams. Ultrasonographic evaluations were used to measure uterine horn diameter on the day of AI and to confirm pregnancy 35 days post-AI. The variables analyzed to identify factors affecting pregnancy included breed, body condition score (BCS), age, breeder (I or II), treatment group (TI or TII), time of AI, and uterine horn diameter. Logistic regression and machine learning analysis identified uterine horn diameter, ewe age, and synchronization protocol as significant predictors of pregnancy. Uterine horn diameter averaged 10.8 mm in TI and 10.1 mm in TII. Younger ewes had a higher pregnancy rate than older ones, and the pregnancy rate in TI (14-day protocol) was significantly higher at 78.3%, compared to 46.7% in TII (12-day protocol) (P < 0.001). In conclusion, under field and high-altitude conditions, key factors influencing pregnancy in ewe lambs subjected to estrus synchronization include uterine horn diameter, age, and the synchronization protocol used. The 14-day protocol yielded a significantly higher pregnancy rate than the 12-day protocol.

Instituciones: Universidad Nacional del Altiplano; Universidad Nacional Amazónica de Madre de Dios