Abstract
The effect of pregnant mare serum gonadotropin (PMSG) on follicle stimulating hormone (FSH) and estradiol concentrations was studied in 14 prepuberal gilts. At 157 ± 3 days of age, gilts were randomly assigned to receive a single subcutaneous injection of either saline (C; n = 7) or 1000 IU of PMSG ( n = 7). Treatments were administered at 08.00 h. Blood was collected on days −2, −1, 0, 1, 2, 3 and 4 (day 0 = day of injection). Samples were taken at 15-min intervals between 08.00 and 12.00 h and 20.00 h and 24.00 h. Additional samples were taken every 2.67 h between 24.00 and 08.00 h and 12.00 and 20.00 h. Concentrations of FSH during the preinjection period were similar ( P < 0.05) between the two treatments (C; 4.4 ± 0.5 vs PMSG; 4.5 ± 0.7 ng/ml). Mean plasma concentrations of FSH post injection were 4.8 ± 0.9 and 3.4 ± 0.8 ng/ml in C and PMSG gilts, respectively, and were not different ( P > 0.05). Mean daily FSH concentrations decreased ( P < 0.06) from 4.4 ± 0.06 ng/ml on day 0 to 2.6 ± 0.7 ng/ml on day 4 in PMSG gilts. Mean daily concentrations of estradiol were higher ( P < 0.05) on days 2, 3 and 4 in gilts receiving PMSG when compared to C females. Laparoscopic examination of the ovaries on day 6 revealed that the PMSG-treated gilts had ovulated while the C gilts did not. These results indicate that PMSG stimulated follicular growth and ovulation in prepuberal gilts with no increase in plasma concentrations of FSH.
Published Version
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