Ovulation induction in pre-pubertal Sahiwal-Friesian cross bred heifers by the use of clomiphene citrate and hCG

In this study, an attempt was made to induce ovulation in crossbred pre-pubertal heifers by the use of clomiphene citrate (an anti-estrogen) and hCG. The hypothesis was that the clomiphene citrate, being anti-estrogen, would remove negative feedback effect of estrogen on the release of pituitary gonadotropins. Elevated gonadotropins would support ovarian follicular growth to a point where hCG would induce ovulation. Six pre-pubertal heifers were given clomiphene citrate orally at 300 mg/heifer for 9 days. At the same time, six control heifers were given placebo tablets. On following day, hCG was given to all heifers at a dose of 2500 IU. Blood was collected before, during and after treatment and plasma was assayed for progesterone (P4) and estradiol (E2) concentrations. Five heifers (83.3%) in the experimental group had E2 concentrations above 10 pg/ml compared to one heifer (16.7%) in control group. Due to a wide variation, mean E2 concentration did not differ significantly between experimental and control heifers. The P4 assays showed that four heifers (66.7%) in the experimental group had ovulated (P4 > 1 ng/ml plasma) compared to one heifer (16.7%) in control group, and mean P4 concentration differed (P < 0.05) when concentrations were greatest in the clomiphene citrate-treated heifers. In conclusion, clomiphene citrate along with hCG can be used to induce ovulation in pre-pubertal heifers.