Mathematical model of the bovine estrous cycle

Bovine reproduction and fertility is studied extensively, especially because dairy cow fertility has declined during the last decades. The regulation of estrus is controlled by the complex interplay of various organs and hormones. Mathematical modeling of the bovine estrous cycle could help in understanding the dynamics of this complex biological system. We developed a mechanistic model of the bovine estrous cycle that includes the processes of follicle and corpus luteum development and the key hormones that interact to control these processes. The model contains 12 ordinary differential equations and 51 parameters. The model generates estrous cycles of 21 days, with three peaks of follicle stimulating hormone and three corresponding waves of follicular growth. Progesterone, which is high during the first two waves, decreases as the corpus luteum regresses under prostaglandin influence. The third follicular wave results in increasing levels of estradiol. This causes a surge of luteinizing hormone, which triggers ovulation. Simulations show that a set of equations and parameters was obtained that describes the system consistent with empirical data. The model could be used as a basis for more elaborate models, that include parameters in the field of e.g. energy metabolism, stress, and estrous behavior.