Assisted Reproductive Technologies in Small Ruminants

Assisted reproductive technologies (ART) have transformed breeding and conservation in small ruminants such as sheep, goats and deer. Key methods include artificial insemination, superovulation, embryo production, cryopreservation and embryo transfer. Artificial insemination permits efficient dissemination of superior genetics across flocks and conservation herds, reducing the need for animal transport. Superovulation protocols using exogenous gonadotrophins yield multiple oocytes per cycle, feeding in vivo or in vitro embryo production pipelines. In vitro production has matured through improved oocyte maturation, fertilisation and blastocyst culture, while cryopreservation techniques such as slow freezing and vitrification support global germplasm exchange and genetic resource banking. Embryo transfer and non-surgical transcervical approaches are becoming increasingly feasible in sheep and goats despite anatomical challenges posed by cervical folds. Recent integration of genome editing via CRISPR/Cas in early embryos enables precise genetic improvement alongside conventional ART. These advances, underpinned by hormonal synchronisation, novel devices and culture platforms, have global significance for sustainable livestock production, biodiversity conservation and biomedical research models. Ongoing efforts focus on optimising protocols for field conditions, minimising invasiveness and enhancing conception and lambing rates across breeds and environments.

Research from Nature Portfolio

Recent studies have demonstrated the effectiveness of transcervical artificial insemination in a small cervid species. By comparing cervical immobilisation and traction techniques with and without oxytocin-induced dilation, researchers achieved rapid cervical passage and semen deposition in 50% of attempts, yielding conception rates of around 50%. Procedures completed in under twenty minutes were deemed satisfactory and are proposed as promising methods for conservation efforts and potential adaptation to other ruminant breeding programmes.

Assisted Reproductive Technologies in Small Ruminants publication trend

The graph below shows the total number of articles in assisted reproductive technologies in small ruminants across all publications each year (not limited to Nature Index journals).

Technical terms

Superovulation: The administration of exogenous hormones to stimulate the development of multiple ovarian follicles within a single reproductive cycle.

Embryo transfer (ET): The placement of embryos, produced in vivo or in vitro, into the uterus of a recipient female to establish pregnancy.

Vitrification: A rapid cryopreservation technique that transforms biological samples into a glass-like state, minimising ice crystal formation and improving post-thaw survival.

Transcervical artificial insemination: A non-surgical method of depositing semen into the uterus through the cervix, often involving cervical dilation aids.

Multiple ovulation and embryo transfer (MOET): A combined protocol of superovulation, embryo collection and transfer to multiple recipients to maximise offspring from superior females.

CRISPR/Cas system: A genome editing platform that utilises RNA-guided nucleases to introduce precise genetic modifications in zygotes and early embryos.

References

1. Transcervical artificial insemination in the brown brocket deer (Subulo gouazoubira): a promising method for assisted reproduction in deer. Scientific Reports (2023).
2. Towards Improving the Outcomes of Multiple Ovulation and Embryo Transfer in Sheep, with Particular Focus on Donor Superovulation. Veterinary Sciences (2022).
3. Induction of cervical dilation for transcervical embryo transfer in ewes. Reproductive Biology and Endocrinology (2014).
4. From reproductive technologies to genome editing in small ruminants: an embryo’s journey. Animal Reproduction (2018).
5. Ovarian response to P4‐PGF‐FSH treatment in Suffolk sheep and P4‐PGF‐PMSG synchronization in cross‐bred ewes, for IVD and ET protocol. Veterinary Medicine and Science (2022).