A 4-year old second-lactation Holstein cow that is 150 days in milk has been in anestrus since calving. On palpation of the rectum, a cystic structure that is 3cm in diameter is identified on the left ovary. Administration of which of the following is the most appropriate initial treatment?
a. Follicle-stimulating hormone followed by gonadotropin-releasing hormone in 15 days
b. Gonadotropin-releasing hormone followed by prostaglandin in 15 days
c. Melengesterol acetate followed by prostaglandin in 19 days
d. Prostaglandin followed by melengestrol acetate in 19 days