For livestock it is the value of the main product (milk, eggs, lamb, pork) plus the value of any secondary product (calf, wool) minus the cost of replacement.
Ar gyfer da byw, mae'n golygu gwerth y prif gynnyrch (llaeth, wyau, cig oen, porc) ynghyd â gwerth unrhyw gynnyrch eilaidd (llo, gwlân) llai y gost amnewid.