ICSI: miracle tool or misunderstood risk?

As ICSI becomes routine in sport horse breeding, Oscar Williams examines the science, the performance data and the myths that refuse to fade

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INTRACYTOPLASMIC sperm injection – better known as ICSI – was once a niche technique in sport horse breeding. Now it is increasingly routine, producing foals long after a stallion’s death and from mares still competing at the highest level.

Yet hesitation persists. In some breeding circles – and under plenty of social media posts – ICSI-born horses are still dismissed as “less robust” or “test tube horses”.

The unease is not entirely surprising. When ICSI entered equine reproduction in the late 1990s, there were no mature competition horses to assess and no long-term data to reassure sceptics. The technique also arrived in the shadow of wider assisted-reproduction debates in humans, where science often advanced faster than public understanding.

“In the early years, there was a natural degree of caution,” says Lorna Wilson of Elite Stallions, whose team were the first to offer commercial ICSI services in the UK. “It was new, and people didn’t fully understand the process. When that’s the case, assumptions can fill the gap.”

Some of that hesitation was instinctive rather than evidence-based. During a 2023 British Equine Veterinary Association debate, Professor Madeleine Campbell described the “yuck factor” – a general unease around technologies perceived to interfere with nature. Confusion with cloning, a separate and more invasive procedure associated with documented complications, has also contributed to lingering concern.

Over time, “we don’t yet know” in some quarters evolved into “there must be a problem”. Anecdote travels faster than data, and isolated disappointments – inevitable in any programme – were sometimes attributed to conception method rather than genetics or management.