Seasonal variation in the reproductive hormones of male goats

The aim of this work was to study the circannual plasma profiles of LH, PRL, testosterone (T) and estrone sulfate (E1S) in different periods of the year and to characterize the possible variations in LH and PRL release patterns. We also tried to verify a possible relationship between plasma PRL fluctuations and ambient temperature, as well as the influence of an acute stress condition on levels of plasma PRL. Six adult male goats of the Ionica and Alpine breed reared in Southern Italy (40 degrees N lat.) were subjected to frequent samplings (every 15 min for 6 h) once a month for a whole year. The blood samples were assayed for plasma concentrations of E1S, LH and PRL by radioimmunoassay, and for T by enzymeimmunoassay. The ambient temperature was recorded on each day of bleeding. Sex steroids and PRL showed marked circannual variations, with the highest levels during the summer (July) and the lowest during the winter-early spring (March). The concentrations of plasma LH did not indicate significant seasonal variations. A positive relationship was observed between plasma levels of PRL and E1S and ambient temperature. The patterns of LH release seemed to change depending on season, but this was not an obvious and common feature in all bucks. The hormone concentrations for plasma PRL profiles seemed to be influenced by an acute stress condition (associated with cannula insertion and handling procedures), with the variations more marked when the plasma levels of PRL were low.

Progesterone does not inhibit the increase in pituitary content of luteinizing hormone after removal of estradiol in the ewe

During late gestation in the ewe, the pituitary content of LH is reduced by about 95%, presumably due to the presence of high concentrations of ovarian steroids. The aim of this study was to determine whether the pituitary content of LH in the ewe can increase after long-term administration of ovarian steroids, when only estradiol (E) is removed or if both E and progesterone (P) must be withdrawn to allow synthesis of LH to occur. Ten ovariectomized ewes were treated with implants containing E and P. After 3 weeks of treatment, the E implants were removed from 5 ewes (-E+P) and both steroid implants were removed from the remaining 5 ewes (-E-P). Five ovariectomized ewes received P implants at the beginning of the experiment and these implants were left in place for the duration of the study; 5 ovariectomized ewes served as controls (C). All animals were injected with 100 micrograms GnRH iv 3, 6 and 9 weeks after the initiation of treatment. The area under the LH-response curve was used as an indication of the pituitary content of LH. All steroid treatments markedly reduced basal levels of LH. LH levels increased only in -E-P ewes, beginning 6 weeks after initiation of the study. After 3 weeks, -E+P and -E-P ewes released less LH (P less than 0.05) in response to GnRH than did C ewes, whereas P animals did not differ from controls. LH release in response to GnRH in -E+P and -E-P groups had increased by 6 and 9 weeks and was not different from that of C ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproductive performance of female goats given progestagen associated with PMSG and/or HMG in deep anestrus

During deep anestrus and after a 21-day fluorogestone acetate (FGA) treatment, 200 pluriparous lactating Alpine goats were given randomly one of four treatments: (A) 500 IU of pregnant mare serum gonadotropin (PMSG) 48 h before sponge removal; (B) 500 IU of PMSG 48 h before sponge removal and an ampoule of human menopausal gonadotropin (HMG) at sponge removal; (C) two ampoules of HMG at sponge removal; (D) four ampoules of HMG at sponge removal. All the goats were mated naturally during estrus. The percentage of goats kidding (fertility rate) was 6, 34, 40 and 36% for groups A, B, C, and D, respectively; the number of kids/pregnant female (prolificacy) averaged between 1.33 and 1.72. The accuracy of pregnancy diagnosis on the basis of plasma progesterone concentration 20 to 22 days after mating was not particularly satisfactory, mainly because many pregnant goats, and especially group A goats, showed abnormally prolonged luteal activity. The determination of total estrone 60 days after mating gave almost 100% overall accuracy.

Effects of oestradiol and progesterone on pulsatile secretion of luteinizing hormone in ovariectomized ewes

The effect of treatment with oestradiol, progesterone, a combination of the two steroids or no steroids on pulsatile release of luteinizing hormone (LH) was examined in ovariectomized ewes. Beginning 3 days after ovariectomy, 5 ewes were assigned to each of the following treatment groups: 0.7 mg oestradiol, 16 mg progesterone, 0.7 mg oestradiol plus 16 mg progesterone or no steroid. All treatments were administered twice daily for 3 weeks in a 0.5 ml injection of ethanol given sc. After 2 weeks of treatment and 1, 4, 8, 16 and 32 days after the treatment period ended, blood samples were obtained from all ewes at 10-min intervals for a 6-h period. At the end of the 6-h period, 100 micrograms gonadotrophin-releasing hormone (GnRH) was injected iv and blood samples were collected at 15 min intervals for an additional 5 h to estimate the relative pituitary content of LH. Ovariectomized ewes receiving no steroid presented regular pulses of LH at frequency of four to five pulses during a 6-h sampling period. Treatment with progesterone alone decreased the frequency of pulsatile release of LH to approximately 1 pulse/6 h, but did not affect the amplitudes of the pulses of LH. Recovery of pulsatile release of LH to a frequency of four or five pulses of LH in a 6-h period was complete between 16 ewes. Oestradiol, administered alone or with progesterone, resulted in a decrease in both the frequency and the amplitude of pulses of LH compared to control ewes and a decrease in GnRH-induced release of LH.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma cortisol variations induced in the stallion by mating

Plasma cortisol variations have been determined by radioimmunoassay in 5 stallions during mating and in 2 teasers during oestrous female exposure. In all the animals, cortisol plasma levels consistently increase (71.1 ng/ml vs 44.0 and 63.0 ng/ml vs 35.1, in the stallions and in the teasers, respectively) 7-30 min after female exposure; 120 min after exposure, cortisol concentrations are again low.

Progesterone, estrogen, LH, FSH and PRL concentrations in plasma during the estrous cycle in goat

Progesterone, estrogen, LH, FSH and PRL variations in plasma were measured in 7 goats by RIA. Mean progesterone level was 0.0-0.8 ng/ml in estrus and 1-4 ng/ml in diestrus. Estrogen levels ranged from 10 to 20 pg/ml in diestrus; around estrus, a peak of 26.9 +/- 3.18 pg/ml was observed. LH values were 0.5-3.0 ng/ml with a preovulatory peak (40.7 +/- 10.12 ng/ml) 8 to 24 h after the onset of estrus. Except for a peak (14.0 +/- 3.09 ng/ml) coincident with LH surge, plasma FSH level ranged between 2 and 4 ng/ml. PRL level averaged 2-5 ng/ml in diestrus but high concentrations of this hormone were seen around estrus.

Concentrations of progesterone, 17 alpha-hydroxyprogesterone and 20 alpha-dihydroprogesterone in the plasma of mares during pregnancy and at parturition

Plasma concentrations of progesterone and 17 alpha-hydroxyprogesterone were high in the 2nd and 3rd months of gestation, but 20 alpha-dihydroprogesterone increased from a level of 2 ng/ml, during the first 3 months, to 10-15 ng/ml during months 5-10, to reach 80-120 ng/ml during the last 30 days before foaling.