Superovulation, fertilization and embryo recovery in gonadotropin treated prepubertal calves

Abstract

Prepubertal Angus calves between 4 and 7 months of age, weighing 135 to 180 kg, were randomly assigned to one of four superovulation treatments with seven calves per treatment group. Group I calves were injected intramuscularly (im) with 1200 I.U. of pregnant mare's serum gonadotropin (PMSG). Group II calves were injected with 1200 I.U. PMSG followed in 72 hrs with 50 mg luteinizing hormone (LH) given intravenously (iv). Group III calves were injected (im) twice daily for five days with 5, 4, 3, 2, and 1 mg of follicle stimulating hormone (FSH) respectively, for a total of 30 mg of FSH. Group IV calves were given 30 mg FSH, as in Group III, followed by 50 mg LH (iv) 96 hrs after the first FSH injection. All calves were inseminated by the rectal fixation method with multiple doses of frozen semen. Embryos were recovered surgically or after slaughter 48 to 72 hrs following the last insemination. The ovulation rate was 2.0, 11.3, 2.0 and 21.9 for Groups I, II, III and IV, respectively. Recovery and fertilization rates were 1.1 and 0.3, 8.0 and 5.6, 1.4 and 0.3, and 10.9 and 3.6 embryos for Groups I–IV, respectively. In this study, treatment with LH increased the ovulation, fertilization and embryo recovery rates in calves treated with PMSG or FSH.