Final answer:
Follicular cystic ovary disease in dairy cows, affecting multiple generations, is best described as a hereditary condition because it is passed down genetically.
Step-by-step explanation:
The condition being described is follicular cystic ovary disease in a dairy herd, where several generations have been affected. The correct descriptor for this condition, given its occurrence across generations, is hereditary. This means that the condition is passed down from parent to offspring through their genetic material. A hereditary condition such as this can potentially have a significant impact on the herd's fertility and productivity, making it an important focus of veterinary treatment and genetic management.