Theses and Dissertations Collection

The objectives of the present studies were to determine if chronic administration of a gonadotropin-releasing hormone (GnRH) agonist, Deslorelin, would increase circulating progesterone (P₄) concentrations and subsequently increase pregnancy rates in dairy cattle. Administration of Deslorelin for 12 days increased luteal volume and circulating P₄ concentrations in primiparous dairy cows, but increased only luteal volumes in multiparous cows. Treatment with Deslorelin increased day 45 pregnancy rates in cows compared to untreated controls. Chronic treatment with Deslorelin in dairy cattle; 1) increased luteal volume of the primary CL, 2) induced accessory CL, 3) increased circulating P₄ concentration in primiparous cows only, 4) did not lengthen the estrous cycle, and 5) decreased embryonic death. Although luteal volumes increased in multiparous cows, but not P₄ with Deslorelin treatment, there was an effect on pregnancy rates. This hormonal strategy may represent a suitable model to address local effects of P₄ and GnRH/luteinizing hormone on uterine environment and embryonic survival.