Champion racehorse Frankel shows signs of being as prolific in the breeding barn as the racetrack with a 95 per cent fertility rate reported for his first season at stud.

In his first northern hemisphere season, Frankel covered 133 mares at his owner Khalid Abdullah's Banstead Manor with 126 scanned in foal.

Of the seven mares not in foal, six were pregnant only to suffer early foetal deaths.

In September, Frankel will serve a limited book of mares to southern hemisphere time with multiple Group One winner More Joyous among them.

The Racing Post reported 24 of the mare's in Frankel's first book belong to Prince Khalid's Juddmonte operation and estimated that at a fee of STG125,000 ($A207,468) the stud could expect a return of STG13,625,000 ($A22.61 million) if all the other mares deliver healthy foals.

Frankel's first book included 38 Group or Grade One winners, among them Alexander Goldrun, Danedream and Midday.

Juddmonte general manager Philip Mitchell said Frankel had been an easy stallion to deal with in his first season.

Frankel retired unbeaten last year as the highest rated horse since the introduction of international thoroughbred rankings.

He was trained by Sir Henry Cecil who died last month after a long illness.

Cecil attributed Frankel with keeping him going over the past few years.