The hormonal profile during the estrous cycle and gestation in Damascus goats

Plasma progesterone, estradiol, LH, FSH and prolactin levels were studied before and during an estrous cycle in 11 Damascus does, exposed to different suckling regimens (Group A: does suckled for 60 days; Group B: does suckled for 120 days; Group C: non-lactating does). In addition, plasma progesterone levels were determined during pregnancy in 10 pregnant does. The mean plasma progesterone levels in the lactating does before the onset of the first postpartum estrus, which included the follicular phase, were significantly lower (0.2 ± 0.1 and 0.1 ± 0.02 ng/ml, respectively), compared to the luteal phase (5.4 ± 0.9 and 2.6 ± 0.3, respectively). The mean plasma progesterone levels in non-lactating does prior to and after the onset of the first seasonal estrus were 0.5 ± 0.1 and 3.3 ± 0.4, respectively. A decline in plasma progesterone concentration was observed 24–72 h before the second postpartum (Groups A and B) and seasonal (Group C) estrus, indicating CL regression occurring in all does. The mean plasma progesterone concentrations in pregnant does reached a value of 4.6 ± 2.8 ng/ml at week 2 of gestation, and increased to a level of 24.5 ± 3.1 ng/ml 12 weeks later. During the luteal phase estradiol levels in the does of Groups A–C were lower (45.7 ± 3.1, 30.8 ± 1.4 and 61.04 ± 6.5 pg/ml, respectively) than the first peak, whether at the onset of postpartum (Groups A and B) seasonal estrus (Group C), or during the estrous period (46.1 ± 5.9, 41.6 ± 5.2 and 93.1 ± 39.5 pg/ml, respectively). The difference in the profiles of plasma estradiol levels at the first and the second postpartum (Groups A and B) seasonal (Group C) estrus may be due to the negative effect of progesterone levels. An LH surge was detected in only two lactating does in Group A (59.3 and 33.6 mIU/ml) 24 and 32 h after the onset of the second postpartum estrus following an increase in plasma estradiol concentration. Plasma FSH levels fluctuated in all groups with no distinct trend during the estrous cycle. Prolactin levels at the onset of the postpartum (Groups A and B)/seasonal (Group C) estrus were higher than levels detected before and during estrous period. The Damascus does manifested great variation in hormonal profiles of the individual animals. All does showed normal cycles, not affected by the different suckling regimens or lactation. © 2004 Elsevier B.V. All rights reserved.