Follicular dynamics after treatment with hCG for ovulation induction in mares

In this study the use of hCG for induction of ovulation is described. Factors such as follicle diameter at the time of administration of hCG (3000 IE hCG i.v.), follicular growth after hCG and the rate of double ovulations were evaluated. A total of 168 mares presented for artificial insemination were used. In 249 estrous periods hCG was given to mares exhibiting standing estrous when a minimum follicle diameter of 30 mm and a well developed edema of the endometrium could be detected by ultrasonography. In nine estrous periods ovulation occurred within 24 hours after hCG. The majority of mares (216; 86.7%) ovulated 24 to 48 hours after hCG and in 24 cases ovulation was delayed beyond 48 hours. Follicle size at the time of hCG administration (30-34 mm, 35-39 mm, > or = 40 mm) had no influence on the percentage of mares ovulating 24 to 48 hours after hCG (89.2%, 87.9%, and 83.7%, respectively). Double ovulations could be observed in 17.7% of estrous periods. The one cycle pregnancy rate was not influenced by follicle size (small 45.9%; medium 41.6%; large 47.5%). Repeated treatments with hCG during successive estrous cycles within one year did not influence the rate of responding to hCG. Mares in standing estrous respond well to hCG if a minimum follicle size of 30 mm and a well developed endometrial folding is present.     

LRH─A3、hCG和PMSG对体外培养条件下牦牛垂体组织LH和FSH分泌的调节

促卵泡素３号（ＬＲＨ－Ａ３）、人绒毛膜促性腺激素（ｈＣＧ）和孕马血清促性腺激素（ＰＭＳＧ）等３种外源性激素均可增加体外培养条件下牦牛垂体组织分泌ＬＨ和ＦＳＨ的能力。培养液中ＬＨ和ＦＳＨ含量与加入的ＬＲＨ－Ａ３量呈正相关，与加入的ＰＭＳＧ和ｈＣＧ的量无显著关系     

Plasma LH and progesterone levels before and after ovulation and observation of ovarian follicles by ultrasonographic diagnosis system in dogs

Recently, canine frozen semen has been attracting attention for breeding purposes, and methods of judging ovulation and optimum timing for insemination have become important. As methods of predicting the canine ovulation, vaginal smear, plasma sex hormone levels and ultrasonographic diagnosis system (US) have been investigated in combination, but a standard technique has not yet been established. Therefore, we investigated a method of predicting canine ovulation in dogs by US, and by measuring plasma LH and progesterone (P) levels three times a day. Ovulation could be observed by detecting irregularly shaped ovarian follicles by US in six of 11 dogs (54.5%). In these dogs, the time between the LH peak and ovulation was 24-48 hr, 38.0 hr on average. The P level on the ovulation day was 1.88-2.81 ng/ml, 2.34 ng/ml on average. A value of 1.88 ng/ml was detected in one dog, but the other five dogs showed P levels of 2 ng/ml or higher. The P level on the day before ovulation was 0.8-1.56 ng/ml, 1.12 ng/ml on average. Assuming that ovulation occurred two days after the LH peak in the 11 experimental dogs, the P level was 2.12-4.06 ng/ml, 2.78 ng/ml on average. The period of a high LH level, not less than 10 ng/ml, continued for 12 hr around the LH peak. Based on these findings, to predict ovulation using US and LH level, it would be necessary for the tests to be performed several times a day. In contrast, it was shown that the day on which a plasma P level of 2 ng/ml or higher was detected by the test performed once a day corresponded to the ovulation day.     

Effects of plasma progesterone concentrations on LH release and ovulation in beef cattle given GnRH

The effects of plasma progesterone concentrations on LH release and ovulation in beef cattle given 100 microg of GnRH im were determined in three experiments. In Experiment 1, heifers were given GnRH 3, 6 or 9 days after ovulation; 8/9, 5/9 and 2/9 ovulated (P<0.02). Mean plasma concentrations of progesterone were lowest (P<0.01) and of LH were highest (P<0.03) in heifers treated 3 days after ovulation. In Experiment 2, heifers received no treatment (Control) or one or two previously used CIDR inserts (Low-P4 and High-P4 groups, respectively) on Day 4 (estrus=Day 0). On Day 5, the Low-P4 group received prostaglandin F(2alpha) (PGF) twice, 12 h apart and on Day 6, all heifers received GnRH. Compared to heifers in the Control and Low-P4 groups, heifers in the High-P4 group had higher (P<0.01) plasma progesterone concentrations on Day 6 (3.0+/-0.3, 3.0+/-0.3 and 5.7+/-0.4 ng/ml, respectively; mean+/-S.E.M.) and a lower (P<0.01) incidence of GnRH-induced ovulation (10/10, 9/10 and 3/10). In Experiment 3, 4-6 days after ovulation, 20 beef heifers and 20 suckled beef cows were given a once-used CIDR, the two largest follicles were ablated, and the cattle were allocated to receive either PGF (repeated 12h later) or no additional treatment (Low-P4 and High-P4, respectively). All cattle received GnRH 6-8 days after follicular ablation. There was no difference between heifers and cows for ovulatory response (77.7 and 78.9%, P<0.9) or the GnRH-induced LH surge (P<0.3). However, the Low-P4 group had a higher (P<0.01) ovulatory response (94.7% versus 61.1%) and a greater LH surge of longer duration (P<0.001). In conclusion, although high plasma progesterone concentrations reduced both GnRH-induced increases in plasma LH concentrations and ovulatory responses in beef cattle, the hypothesis that heifers were more sensitive than cows to the suppressive effects of progesterone was not supported.     

PMSG和hCG对猪卵母细胞体外成熟的影响

对猪卵母细胞不同发育阶段的激素需要进行了初步探讨。结果表明 :猪卵母细胞体外培养 48h ,前 2 4h在培养液中加入激素 ,后 2 4h不加激素 ,卵母细胞的A级成熟率 (51 73% )和总成熟率 (83 2 5 % )最高 ,极显著高于前 2 4h不加激素 ,后 2 4h添加激素培养的成熟率 (P <0 0 1 ) ;也显著高于不含激素的培养液连续培养 48h的成熟率 (P <0 0 5) ;但与添加激素连续培养 48h组成熟率差异不显著 (P >0 0 5)。     

Evaluation of ovulation rate and ovarian phenotype in puberal heifers from a cattle population selected for increased ovulation rate

Long-term selection for increased ovulation rate (1984 to 2002) has resulted in a unique ovarian phenotype in the MARC Twinner cattle population. Ovulation rate and frequency of bilateral ovulations were examined by rectal palpation in 29,547 estrous cycles for 3,910 heifers (12 to 18 mo of age) in this population. Bilateral ovulations (one corpus lutuem [CL] on each ovary) were of interest because bilateral twin pregnancies result in decreased dystocia and increased calf survival. Ovulation rate increased linearly at a rate of 0.026 CL per year, and it currently averages 1.48 +/- 0.04 CL per estrous cycle. Concurrent with the increase in ovulation rate, the frequency of triplet ovulations increased from 0% to 2.3 +/- 0.8% (P < 0.001). Ovulation rate of both the right and left ovary increased equally at a rate of 0.013 CL per year, and mean ovulation rate of the right ovary remained greater than mean ovulation rate of the left ovary throughout the study (0.66 vs. 0.55 +/- 0.003 CL per estrous cycle; P < 0.001). Although correlations were low, ovulation rate of one ovary was negatively correlated (P < 0.001; r = -0.07) with ovulation rate of the same ovary in the previous estrous cycle, but positively correlated (P < 0.001; r = 0.13) with the contralateral ovary of the previous estrous cycle. The proportion of bilateral ovulations averaged 55.7 +/- 0.7%, a value greater than the predicted 49.5% (P < 0.001). In addition to dystocia and retained placenta, triplet pregnancies increase the incidence of pregnancies gestating fetuses of opposite sexes and subsequent incidence of freemartins; thus, selection pressure on ovulation rate may need to be adjusted in the MARC Twinner population. The proportion of bilateral ovulations in the population is greater than expected, and this may be an economically important trait, which will respond to selection and be beneficial for improving bovine reproductive efficiency. Understanding factors controlling the increased functional activity of the right ovary and bilateral ovulations may provide further insights into the mechanisms controlling follicle selection and methods to improve reproductive management of cattle.     

The influence of exogenous pituitary growth hormone on the ovulatory response to PMSG and hCG and the LH response to estradiol benzoate in prepubertal gilts

Two experiments were performed to examine the influence of exogenous growth hormone on the reproductive axis in gilts. Experiment one employed 26 Yorkshire × Landrace prepubertal gilts, which were selected at 150 d and 86.5 ± 1.5 kg bodyweight (BW) and assigned equally to two treatments. Gilts received injections of either porcine growth hormone at 90 μg/kg BW, or vehicle buffer, from 150 to 159 d. At 154 d gilts received 500 IU PMSG, followed 96 hr later by 250 IU hCG. Gilts were slaughtered at 163 days and their ovaries recovered to determine ovulatory status. In each treatment, gilts failed to show any ovarian response to PMSG/hCG. All remaining control gilts ovulated and their ovaries appeared morphologically normal. In gilts receiving exogenous growth hormone, fewer ovaries (4/11, P<.01) appeared morphologically normal. The ovaries of all other growth hormone injected gilts had very large (12–25 mm) non-luteinized follicles. In experiment two, 20 prepubertal Yorkshire × Landrace gilts were selected at 138 days and 85 kg BW. These gilts received injections of growth hormone at 90 μg/kg BW (n=9) or vehicle (n=11) from 138 to 147 days. At 143 days, all gilts were given an injection of estradiol benzoate (EB) at 15 μg/kg BW. Blood samples were taken at the time of EB injection, at 24 and 36 hr and then at 6 hr intervals until 78 hr. All samples were assayed for serum LH concentrations. The EB induced LH peak height was lower (P<.04) in gilts receiving exogenous growth hormone than in controls. The results presented indicate that the daily injection of growth hormone at 90 μg/kg BW reduced the estradiol-induced release of LH in addition to reducing the number of corpora lutea in gonadotrophin stimulated gilts.     

Dynamics of ovarian follicular development in cattle during the estrous cycle, early pregnancy and in response to PMSG

Ovarian follicular dynamics of cattle were examined during the estrous cycle, early pregnancy and in response to PMSG. Number and size of follicles were monitored by ultrasonographic examinations. During the estrous cycle, distinct periods of follicular dominance (measured by the increase in difference in size between the largest and second largest follicle) occurred in both the luteal (Days 6-8) and proestrus (18-22) phases of the estrous cycle (two follicular waves). Associated with the well timed development of the first dominant follicle was a change in distribution of follicle numbers in small (less than 5 mm; increased on Days 2-4), medium (6-8 mm; increased on Days 3-5) and large (greater than or equal to 9 mm; increased on Days 6-9) follicular size classes. Follicular development was greater on the ovary bearing the CL for the period that the CL was present. The dominant follicle formed during the first follicular wave was capable of ovulating (6 of 8 heifers) following an injection of a synthetic analogue of prostaglandin F-2 alpha on Day 9 of the estrous cycle. During early pregnancy (Days 6-34), follicular development (size of largest follicle, number of follicles and total accumulated size of all follicles) on the ovary bearing the CL was suppressed between Days 24 and 34 of pregnancy. This was a local effect in that follicular development was sustained on the contralateral ovary. Therefore, the CL or conceptus may be regulating follicular development in a manner to help prevent luteolysis. Associated with the injection of PMSG was an initial increase in the number of small follicles followed by their recruitment into medium and large size classes leading to ovulation. Number of follicles greater than 5 mm on the Day of estrus was related (r = .97) to the number of subsequent embryos and oocytes collected. Ultrasonography is a valuable technique to monitor ovarian follicular dynamics in cattle, and can thereby be used to infer changes in physiological and endocrine states.     

FSH and LH concentrations preceding post-partum ovulation in the mare

Equine follicle stimulating hormone (FSH) and luteinizing hormone (LH) were measured in the serum obtained from pregnant mares, bled daily, from up to 17 days before parturition until the first ovulation after parturition. LH was at baseline levels until 2 days before ovulation when it started, and continued, to rise until after ovulation. FSH surges occurred at approximately 24 and 14 days before this post-partum ovulation (12 and 2 days before parturition), thus showing a similar pattern to the cyclic mare, consistent with the hypothesis that 2 surges at these times prepare and prime follicles for subsequent ovulation. The high plasma oestradiol levels that occurred during and immediately before these FSH surges did not show a negative feedback, or the inverse relationship between FSH and oestradiol which occurs in the cyclic mare, and in other species.     

The effect of estradiol cypionate (ECP) on ovarian follicular development and ovulation in dairy cattle.

The efficacy of estradiol cypionate (ECP) for synchronizing ovarian follicular development was determined in lactating Holstein-Friesian cattle. In Experiment 1, 13 cattle were given simultaneous intramuscular (i.m.) injections of 100 mg progesterone and 0 (control), 0.5 or 1.0 mg ECP on Day 3, after a synchronized ovulation (Day 0). Maximum diameter of the dominant follicle of Wave 1 was significantly larger in control cattle than in those given 0.5 or 1.0 mg ECP (means: 15.7, 13.2, and 12.9 mm, respectively). Mean day of emergence of Wave 2 was significantly later in controls than in those given 1.0 mg ECP, with the 0.5 mg group intermediate (Days 10.2, 8.8 and 9.5, respectively). In Experiment 2, 14 cattle were given a CIDR-B and IM injections of 1 mg ECP and 50 mg progesterone without regard to stage of cycle (treatment = Day 0). On Day 8, the CIDR-B was removed and 500 micrograms cloprostenol injected, IM. Mean days of wave emergence (Day 3.4; range: -2 to 7) and ovulation (Day 12.1; range: 10 to 14) indicated that ECP had limited efficacy for synchronizing follicular development and ovulation in dairy cattle when given at random stages of the estrous cycle.