Effect of clomiphene citrate and human chorionic gonadotropin (hCG) on ovulation induction in prepubertal Sahiwal heifers

摘要

Objective: To evaluate the ovulation inducing effect of clomiphene citrate along with human chorionic gonadotropin (hCG) in prepubertal Sahiwal heifers. Clomiphene citrate (an anti-estrogen) causes gonadotropin secretion from pituitary gland by removing the negative feedback effect of estrogen. This causes more FSH secretion which ultimately stimulates follicular growth and upon hCG administration (luteinizing hormone activity) ovulation occurs. Methods: Twelve prepubertal Sahiwal heifers were divided into experimental and control groups, with six animals in each group. The grouping of animals was made on the basis of plane ovary. The status of ovarian puberty was checked through rectal palpation and history of previous estrus signs. Experimental heifers were given clomiphene citrate at 300 mg/heifer for 9 d orally, while heifers in control group were given placebo tablets. The dose of clomiphene citrate was selected on the basis of previous literature. On day 10, hCG (IVF-C 5000 iu (hCG) LG Life Sciences, Korea) was given to all heifers of both groups at 2500 IU/heifer through intravenous route. Two base line blood samples were collected before start of the treatment at each rectal palpation examination for selection of animals. Subsequently, during and after treatment three blood samples per week (on alternate days) for 4 weeks were collected for measuring the progesterone (P4) in serum. The concentration of progesterone was measured though enzyme linked immunosorbent assay. For the comparison of variables, student t-test was applied. Results: The P4 concentrations in five heifers (83.3%) in the experimental group with (P4 > 1 ng/mL) and one heifer (16.7%) in the control group along with corpus leuteum on ovary showed ovulation. One heifer in control group ovulated that might be due to hCG. Mean progesterone concentration was significantly higher (P < 0.05) in treated heifers than in control heifers. Conclusion: Administration of clomiphene citrate and hCG can induce ovulation induction in prepubertal Sahiwal heifers.