Freddy,
If I offer to take back a bull a customer is not satified with for any reason I am the guy taking the risk- NOT the customer. This is particularly true if I don't know my cattle, my customer, or his cattle. By the way I in making recommendations for what bull a customer should buy I am very conservative. If I don't have a bull of the right type i tell him who might. By providing superior customer service and providing an resolution for unhappy customers I would hope to improve the demand and therefor the price of my cattle.
By the way you can get screwed on this deal in the same way Nordstroms fgets a used dress returned to them you can breed someones cows for free by providing a bull. But in the end of the day i would rather have a happy group of customers rather than having them bad mouth me.