Which condition is likely to increase the value of a herd under a disease control program?

A special disease-free certification is likely to increase the value of a herd under a disease control program because it signifies that the animals have been tested and found to be free of specific diseases that can affect livestock health and productivity. This certification can enhance the marketability of the herd, as buyers are often willing to pay a premium for animals that are certified disease-free. It provides assurance that the livestock are less likely to spread diseases, which can lead to higher profits for producers and more reliable supply chains.

In contrast, high feed costs, low demand for livestock, and frequent disease outbreaks can have negative impacts on the herd's value. High feed costs can erode profit margins, low demand can lead to decreased prices, and frequent disease outbreaks can diminish the health and productivity of the herd, making it less desirable to buyers. Therefore, obtaining a special disease-free certification is a proactive measure that directly contributes to increasing the overall value of the herd within a disease control program.