An unproductive animal permanently removed from a productive stock is said to be

An unproductive animal permanently removed from a productive stock is said to be "culled". Culling is the process of selectively removing animals from a herd or flock based on certain criteria, such as poor productivity, poor health, age, or genetic defects. Culling unproductive animals helps to maintain the health and productivity of the remaining animals in the stock. For example, culling a cow that is not producing enough milk will allow the farmer to focus resources on the more productive cows, leading to better overall milk production. Similarly, culling sick animals can prevent the spread of disease to the rest of the herd.