Vouchers (other than the vouchers received when registering and verifying) can now be used to breed. Click on Stables->My Account->Vouchers to redeem. When using a voucher to breed you will receive $10 towards the breeding. If the total of the breeding is less than $10 the remaining amount will be credited to you in the form of voucher credits. Currently voucher credits can only be used to purchase new autogens but that is likely going to be changing.