Superovulatory response and embryo yield in pure Friesian, Inyambo, and crossbreed cows under field conditions in Rwanda

The study aimed to investigate the superovulatory responses and embryo yield in pure Friesian, Inyambo, and crossbreed cows in Rwanda. The research was conducted from 2018 to 2019, using 38 breeding donor cows from the Rwanda Agriculture and Animal Resources Development Board cattle research farms. Donor cows represented five breed genotypes: Inyambo, Friesian, and various crossbreeds (Inyambo × Friesian, Inyambo × Jersey and Inyambo × Sahiwal). Superovulation was induced using two commercial preparations of follicle stimulating hormone (FSH): Stimufol and Pluset, with three inseminations at 12-h intervals. Embryo recovery was conducted on day 7 post-insemination. Factors such as FSH types, donor breed, age, parity, body weight, body condition score, interval from last calving, milk yield, and ovary status were analyzed for their impact on superovulatory responses and embryo yield. A total of 181 embryos were collected, yielding 107 transferable embryos, with a recovery rate of 56.9%. The FSH type and donor body weight significantly (p < 0.05) influenced superovulatory responses and embryo yield, the number of developed corpora lutea, total flushed structures (unfertilized ova and embryos), viable embryos, and embryo stages. Stimufol-treated donors contributed 83.8% of viable embryos. Well-conditioned donors weighing 300-400 kg and 500-600 kg yielded higher numbers of viable embryos. This study showed that there is potential application of MOET in Rwanda's dairy genetic improvement and Inyambo local breed genetic conservation through embryo cryopreservation, Furtherresearch is recommended to explore factors influencing bovine embryo recovery rates for sustainable practice.