It prevents clear testing cattle from being moved out of the herd at a time when there is a higher risk of the herd losing OTF status in the near future.
Mae'n atal gwartheg sydd wedi cael prawf clir rhag cael eu symud allan o'r fuches ar adeg pan fo mwy o risg i'r fuches golli ei statws OTF yn y dyfodol agos.