A genetics company which provided defect bull semen to farmers last year has received a warning from the Commerce Commission about its marketing.
About 900 farmers were affected after they used semen from a bull called Matrix to artificially inseminate their herds.
Matrix, who belonged to Livestock Improvement Corporation (LIC), sired around 6000 calves, of which 1500 heifers were born carrying a genetic defect.
The defect typically caused excessive hairiness and an intolerance to heat, which could affect the animals' ability to produce milk in the future.
A complaint was made to the Commerce Commission in October and the regulator has now served LIC with a compliance advice letter.