A clinical investigation into the effects of prednisolone treatment on ovarian function in heifers

Four heifers displaying regular oestrus were treated daily with 30 mg prednisolone per 100 kg body weight from day 2 after oestrus (i.e. the day after ovulation) until slaughter. Two of the heifers were slaughtered on day 13 and the remaining two on day 26 after last oestrus. Three heifers that had regular oestrus cycles served as untreated controls. Both the treated and the untreated heifers were inspected and examined by rectal palpation during the period of treatment and the findings were compared. The control heifers had all normal ovarian function. In the prednisolone treated heifers, the corpora lutea were found to be small in size compared to the controls. Follicular activity also seemed to be increased. In spite of small corpora lutea and increased follicular activity, none of the prednisolone treated heifers showed signs of oestrogen influence, and the two animals slaughtered 26 days after the start of treatment, did not ovulate or show signs of oestrus. The effect of long-term treatment with corticosteroids on the development and function of the corpus luteum and on follicular activity, and the importance of corticosteroids in the pathogenesis of anovulatio and follicular cysts are discussed.