Cystic ovarian disease (COD) has been recognized as a managerial and financial problem on dairies for almost two centuries. In spite of the large body of literature regarding COD, the etiology of COD is not entirely understood. Additionally, preventive management is not yet perfected.; This dissertation examines the dynamics of spontaneously occurring cystic ovarian disease (COD). Ultrasonography was used to monitor cows with COD on six dairies in western and central Ohio every Monday, Wednesday, and Friday for five weeks. The specific objectives for this study were to determine: (1) if the use of ultrasonography to select a treatment based on cyst type and/or presence of luteal-like tissue (LLT) would increase estrous expression and pregnancy in cows with spontaneously occurring COD, (2) the biochemical profiles of cows with spontaneous COD, (3) the ovarian dynamics and progesterone profiles of cows following treatment for COD, (4) the association between COD and length of the previous dry period and between COD and the number of days open, and (5) if luteal-like structures induced with gonadotropin releasing hormone (GnRH) in cystic cows are steroidogenically and histologically similar to CL induced in cycling cows and to spontaneously occurring CL in cows with normal estrous cycles. The major results of this research were that when luteal cysts and other LLT are identified via ultrasonography, using prostaglandin F as the treatment may allow an earlier opportunity for breeding and thus potential pregnancy. Biochemical profiles of cows for five weeks following treatment were reported and provided an initial assessment of possible associations between concentrations of clinically important metabolites and COD. The dry period after the preceding lactation was longer in cows that had ovarian cysts than those that did not. Cystic cows appeared to achieve pregnancy at a similar rate to non-cystic cows in the early postpartum period. It was observed that 2 cows with follicular cysts became pregnant. Luteal-like structures that were induced by GnRH treatment in cystic cows are structurally similar to GnRH-induced accessory CL in noncystic cows with normal estrous cycles and were steroidogenically active in vivo and in vitro.
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