Advances in Intracytoplasmic Sperm Injection (ICSI) Techniques for Ruminant-Assisted Reproduction

Intracytoplasmic sperm injection (ICSI) represents a highly specialized assisted reproductive technique in which a single spermatozoon is directly injected into a mature oocyte. In ruminants, this method has been increasingly applied as an alternative to conventional in vitro fertilization, particularly in situations involving male subfertility, limited sperm availability, or the need to preserve valuable genetics. Successful ICSI requires advanced micromanipulation systems, rigorous control of laboratory conditions, and a solid understanding of the cellular and molecular mechanisms of oocyte activation and early embryogenesis. Compared with traditional fertilization procedures, ICSI offers several advantages, including reduced dependency on sperm motility, suitability for severely compromised semen, and enhanced opportunities for genetic rescue and conservation. However, the technique also presents challenges in ruminants, such as the frequent requirement for artificial activation, variable sperm nuclear decondensation, species-specific ooplasmic responses, and generally lower developmental rates compared with other livestock species. Optimization of sperm selection methods, micromanipulation tools, and activation protocols has shown potential to improve outcomes, with emerging transcriptomic and proteomic biomarkers providing new strategies for evaluating oocyte competence and guiding embryo development. The aim of this chapter is to present the ICSI technique as applied in ruminant reproductive biotechnology, with emphasis on its practical implementation, technological advancements, and demonstrated impact on reproductive efficiency, genetic preservation, and research applications in cattle, sheep, and goats.