Comparative Evaluation of Serum and Milk Progesterone and 17β-Estradiol Levels in Artificially Induced and Naturally Lactating Dairy Cattle

The study was conducted on 30 crossbred cattle divided into three groups of 10 animals each. Group I served as the control and consisted of nine crossbred Holstein Friesian (HF) and one Jersey cow without any treatment. Group II and Group III comprised repeat-breeding heifers (nine crossbred HF and one Jersey in each group) and received hormonal treatments. Both treatment groups were administered 17β-estradiol (0.1 mg/kg body weight/day) and progesterone (0.25 mg/kg body weight/day) from day 1 to day 7, given twice daily at 12-hour intervals. Group II additionally received dexamethasone (20 mg/animal/day) on days 18 to 20, while Group III was administered reserpine (5 mg/animal/day) intramuscularly on days 8, 10, 12, and 14. Milk samples were collected from induced animals from day 20 of the experiment on alternate days up to day 21 of lactation. Control milk samples were collected from naturally parturated animals at similar intervals from the day of calving. Samples were preserved using potassium dichromate and sodium chloride. Serum and milk concentrations of 17β-estradiol and progesterone were significantly elevated (P