Serum progesterone and oestradiol–17ß concentration in oestrus-induced prepubertal heifers

Abstract

Prepubertal indigenous heifers (20) were treated for induction of puberty with norgestomet ear implant. Ten prepubertal heifers served as control. All treated heifers exhibited oestrus after 27 to 32 h of implant removal while it was after 5 to 13 months of placebo treatment in control heifers. The mean serum progesterone concentration ranged between 0.16±0.02 and 0.18±0.01 ng/ml and that of oestradiol–17ß was between 12.66±0.75 and 14.33±1.52 pg/ml prior to the treatment. Serum progesterone was significantly higher in treated than in control heifers on day 5 of implantation and day of implant removal. The level declined on the day of oestrus, however, while compared on the basis of subsequent ovulation, the concentration was significantly lower in ovulated than in non-ovulated heifers of both treated and control groups. Thereafter, serum progesterone level showed normal trend being significantly higher in ovulated than in non-ovulated heifers of both the groups. The serum oestradiol–17ß concentration in treatment group increased significantly on day 5 of implantation, day of implant removal and on the day of oestrus in both ovulated and non-ovulated heifers as compared to that of control group. And a significantly lower value was registered on days 9 and 16 post onset of oestrus than that at oestrus in treated heifers, however, in control heifers the decrease was not significant. The serum oestradiol concentration on days 9 and 16 post onset of oestrus increased significantly in non-ovulated as compared to ovulated heifers of treated group.