What does estrus indicate?

Estrus is a specific phase in the reproductive cycle of mammals, characterized by the female being sexually receptive and fertile. This period is often referred to as "heat" and is closely linked to ovulation—the release of an egg from the ovary. During estrus, the behavioral signs of receptiveness to mating are noticeable, and the female is capable of conceiving. The hormonal changes that occur during this time prepare the female's body for possible fertilization, making it a crucial time for breeding.

In contrast, ovarian inactivity refers to periods in the reproductive cycle where no significant hormonal activity occurs, and follicle annoyance is not a recognized term in veterinary reproductive biology—it likely refers to discomfort rather than a reproductive phase. The non-breeding season also does not indicate estrus; rather, it describes a time when animals are not in a breeding state, which occurs outside of the estrus periods. Thus, option B accurately reflects the meaning of estrus as it correlates directly with true heat and ovulation in the context of reproduction.