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One of the bull calves was brown and the other was black and shared similar facial markings.
As it turned out, she had twins last month.
''It is the first set of twins I have seen in 50 years,'' Mr Ridder said.
''They are not really common.''
The couple have Pondora Downs, a 16ha lifestyle block near Alexandra, and run a few Hereford/Angus cattle.
He said the mother was an Angus-cross from a Hereford father.
''She was extra big.
''We thought she had pinched one calf off another cow, but then that one calved as well.''