There was a surprise for Jim and Grainne Kirwan from Shannon Harbour, Offaly, last night when one of their cows gave birth to twins from different sires.

At 12.30am this morning the cow, a three-year-old second calver, gave birth to a Hereford bull and a Friesian heifer with minimal assistance.

On Jim's farm, a Hereford bull and a Friesian bull run with the 80-cow herd. He sourced both bulls from Trevor Dudley in Thurles, Tipperary.

Jim told the Farmers Journal that both calves are doing well and the cow has taken to them both.

Dr. Alan Kelly, a lecturer in UCD in Animal Science, says this is an extremely rare event.

“Twin births in itself is rare - around 2% or a one in 50 chance of having a twins.

A twin is generally a double ovulation instead of a single ovulation, i.e. two eggs fertilised instead of one. That is the case here as the calves obviously have a different sire. What is extremely strange here is that this happened through natural service (not artificial insemination)."

"So both bulls must have inseminated that cow at nearly the same time; but strangely the semen of either only fertilized one egg, not both. That would be quite rare especially in natural breeding”.