Not sure it matters the colour of the cow but use on cows with NO clubbie blood. We have had 4 calves by him. Three were out of cows that have never had a crippled calf but, one was a Meyer/angus, one a Habanero/angus and cant remeber the other. All three were a reck and bulls. The only good one was a heifer out of a reciep cow and a clean up bull we had . She was and is good and is still sound.