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PubMed2004

Treatment of suckling beef cattle with a progestagen sponge and oestradiol benzoate or equine chorionic gonadotrophin.

The ovarian responses of anoestrus beef cows to a combined treatment with medroxy-progesterone acetate (MAP) sponges and oestradiol benzoate or equine chorionic gonadotrophin (eCG) were evaluated. Forty-five suckling Hereford cows were allocated to three equal groups. Group 1 received a MAP sponge for seven days plus an injection of 2 mg oestradiol benzoate when the sponge was inserted (day 0) and 1 mg when the sponge was withdrawn; group 2 received identical treatment until day 7, when a dose of 400 iu of eCG was administered, and group 3 were left untreated as control animals. From day 0 to day 11 the cows' ovaries were examined daily by transrectal ultrasonography, and their oestrous behaviour was observed from 24 hours to 96 hours after the sponge was removed. Data from cows that had a corpus luteum present before the sponge was withdrawn were not used in subsequent analyses; there were four in group 1, five in group 2 and four in group 3. In 19 of the 21 cows in groups 1 and 2 a new follicular wave was observed to emerge at a mean (sd) interval of 3.9 (0.3) days after the insertion of the sponge, whereas in group 3 it occurred in all 11 cows after 3.4 (0.6) days. Only the six cows that had a follicle of 9 mm or larger in diameter ovulated (P < or = 0.001). Nine of the 11 cows in group 1 came into oestrus, compared with two of the 10 in group 2 and none of the control cows (P < or = 0.001). Ovulation was observed in four, two and none of the cows in groups 1, 2 and 3, respectively.

Administration, Intravaginal↗
PubMed2004

Effects of a synthetic progestogen, altrenogest, on oestrus synchronisation and fertility in miniature pigs.

Groups of six, six and eight miniature gilts, respectively, received 5, 10 or 15 mg/day of altrenogest for 18 days, and the numbers of corpora lutea and residual follicles were counted approximately 14 days after the treatment by an exploratory laparotomy. They were compared with the numbers in a control group of eight gilts which were examined six to eight days after oestrus. The interval between the last dose of altrenogest and the onset of oestrus increased with the dose of altrenogest, and was significantly longer after the treatments with 10 or 15 mg/day than after 5 mg/day (P < 0.01). Significantly more corpora lutea were observed in the gilts receiving 5 or 10 mg/day of altrenogest than in the control gilts (P < 0.1). Groups of six, seven and six miniature gilts that had respectively received 5, 10 or 15 mg/day of altrenogest were artificially inseminated; four, six and five of the gilts in these groups farrowed, and their mean (sd) litter sizes were 5.5 (2.4), 6.8 (1.2) and 5.0 (2.3), respectively. All six of a group of control gilts farrowed and their mean litter size was 5.8 (1.2).

Animals↗
PubMed2004

Effect of teasing, mechanical stimulation and the intrauterine infusion of saline on uterine contractions in mares.

Uterine motility may have significance for the transportation of spermatozoa and the elimination of the ejaculate and inflammatory products after mares have been covered. The effect of some of the component stimuli of coitus on uterine contractions was investigated by using M-mode ultrasound. The number, amplitude and duration of the uterine contractions of each uterine horn and of the uterine body were measured in oestrous mares for four minutes before and four minutes after teasing by a stallion, mechanical stimulation of the vagina and cervix, the intrauterine infusion of 80 ml of sterile saline, the intrauterine infusion of 10 ml of sterile saline, the intrauterine infusion of 150 ml of sterile saline, and the transcervical passage of a uterine catheter. Teasing by a stallion did not affect the total number, mean amplitude or mean duration of the uterine contractions. Mechanical stimulation of the vagina and cervix increased the total number of uterine contractions, but did not affect the amplitude or duration of the contractions. The intrauterine infusion of 80 ml of sterile saline resulted in an increase in the total number of contractions and a significant increase in the mean amplitude and the mean duration of the contractions in the uterine horns but not the uterine body. The intrauterine infusion of 10 ml of sterile saline caused a significant decrease in the number of uterine contractions in the uterine horns, but had no effect on the contractions of the uterine body. The infusion of 150 ml of sterile saline reduced the number of contractions in the uterine horns but not the uterine body, and did not affect the mean amplitude and mean duration of the contractions. The transcervical insertion of a catheter reduced the number of contractions in the uterine horns, but did not affect the amplitude or duration of the uterine contractions.

Animals↗
PubMed2006

Factors affecting the monetary return from programmes for synchronising oestrus in dairy cows with gonadotrophin-releasing hormone and prostaglandin F2alpha.

Synchronisation, using a combination of gonadotrophin-releasing hormone and prostaglandin F2alpha injections, is commonly used to control the reproductive cycle of dairy cows. A simple model that could predict the monetary return from synchronisation would be a valuable tool in determining whether it would be worthwhile. This study used data from three controlled clinical trials to investigate the effects of six factors (interval between calving and synchronisation, 21-day submission rate, number of cows synchronised, average age, pregnancy rate of non-synchronised cows and season) on the return from synchronisation. The results suggests that the herd's submission and pregnancy rates, the time between calving and synchronisation, and the number of cows synchronised can all significantly affect the return from synchronisation, but only time since calving significantly affected the return in all three trials. They also suggest that there is no simple linear relationship between these factors and the return from synchronisation.

Age Factors↗
PubMed1976

Fundamental aspects of ovum transfer in cattle.

Although it may ultimately be possible to fertilise ovarian follicular oocytes in vitro, superovulation and insemination are currently the only practical method for obtaining a supply of fertilised ova. It is likely that this will remain true for sometime to come. Pregnant mares serum gonadotrophin (PMSG) is almost universally used for inducing superovulation, and response to it has recently been more reliably achieved by using, in addition, prostaglandin F2alpha to induce oestrus in superovulated donors. The recovery of fertilised ova from donors depends on the expected site of the ova within the genital tract, but both surgical and non-surgical methods involve suspending the ova in a stream of fluid which is collected into glass cups and examined microscopically. A variety of in vivo and in vitro environmental conditions affect the success of transfer of fertilised ova. These include the healthy state of the recovered ovum, the storage medium, the method and length of storage, the age of the ovum and the synchronisation of oestrus of donor and recipient.

Animals↗
PubMed1997

Comparing the clinical utility of GnRH antagonist to GnRH agonist in an oocyte donation program.

A potent gonadotropin-releasing hormone (GnRH) antagonist (Nal-Glu) was administered to downregulate the pituitaries of oocyte donors (n = 15) and block their midcycle luteinizing hormone surges. Donors received Nal-Glu at a dose of 50 microg/kg/day i.m., beginning when lead follicles reached a mean diameter of 14 mm. All donors had previously undergone controlled ovarian hyperstimulation cycles using GnRH agonist (leuprolide acetate) administered subcutaneously beginning during the midluteal phase. Ovarian stimulation was performed using human menopausal gonadotropin (hMG). Compared to previous stimulated cycles using agonist and hMG, cycles with antagonist and hMG demonstrated a significant decrease in the amount of hMG required for follicle stimulation (24.7 +/- 1.8 vs. 31.3 +/- 2.5 ampules; p < 0.05). There was also a significant reduction in the number of patient visits necessary per cycle (5.1 +/- 1.4 vs. 9.3 +/- 1.1; p < 0.05) and the required duration of treatment to accomplish a cycle (27.1 +/- 5.3 vs. 11.3 +/- 1.3 days; p < 0.05). However, there were no differences noted in the number of oocytes retrieved (10.7 +/- 4.5 vs. 13.0 +/- 6.3), the fertilization rate of oocytes (60.3 +/- 10.2 vs. 53.9 +/- 11.6%), or the number of embryos obtained per recipient (5.5 +/- 3.2 vs. 7.6 +/- 5.3). Clinical pregnancies occurred in 7 of 15 transfer cycles to recipients. There were no serious adverse side effects experienced by donors using antagonist. We conclude that the use of GnRH antagonist significantly reduces the amount of medication and the time required for ovarian hyperstimulation and that is a useful adjunct in cycling oocyte donors.

Adult↗
PubMed1984

Pituitary content of gonadotropins and receptors for gonadotropin-releasing hormone (GnRH) and hypothalamic content of GnRH during the periovulatory period of the ewe.

Studies were undertaken to determine if the number of hypophyseal receptors for GnRH changes at the time of the preovulatory surge of LH in ewes. Concentrations of LH, FSH, progesterone, and estradiol in serum and concentrations of LH and FSH in pituitary were measured. The content of GnRH in the hypothalamus was also determined. Estrus was synchronized in 35 cross-bred ewes by injecting prostaglandin F2 alpha (PGF2 alpha) at 0 and 4 h (7.5 mg each, im) on day 14 of a naturally occurring estrous cycle, followed 30 h later by the injection of estradiol (25 micrograms in safflower oil, im). Five ewes were killed at each of the following times relative to the first injection of PGF2 alpha: 0, 24, 32, 44, 50, 56 and 96 h. Blood samples were collected throughout the course of the experiment. Concentrations of progesterone in serum decreased markedly by 8 h after PGF2 alpha and were uniformly undetectable (less than 300 pg/ml) by 34 h. Concentrations of estradiol in serum increased after the injection of estradiol and returned to basal values 10 h later. Surges of LH, which were usually coincident with surges of FSH, occurred between 43 and 53 h. Concentrations of both LH and FSH in the pituitary declined after the LH surge. There were no significant changes in the amount of GnRH contained in the preoptic area, the median eminence, or the hypothalamus. The number of receptors for GnRH increased at 24 and 32 h compared to the 0 h value and remained elevated at 44 and 50 h. After the LH surge (56 h), the number of GnRH receptors declined and at 96 h was not different from the number measured at 0 h. Since an increase in the number of receptors will result in the formation of more receptor-hormone complex and may lead to an augmented response, these data suggest that an increase in the number of hypophyseal receptors for GnRH may contribute to the preovulatory LH surge in ewes.

Animals↗
PubMed1993

Induction of oestrus in cats by photoperiodic manipulations and social stimuli.

The development of the nervous system can be studied only if the age of the embryo is exactly known. Since it is difficult to control reproduction in female cats, we tried to time fertilization very precisely to within one hour by using either artificial insemination, or by mating females in oestrus induced by light programming. In one trial, this programming was associated with male or female stimuli according to the work of McClintock (1971, 1978, 1984) and Preti et al. (1986).

Animals↗
PubMed2001

Transfer of canine embryos at various developmental stages recovered by hysterectomy or surgical uterine flushing.

In dogs, embryo transfer (ET) techniques such as induciton of excessive ovulation and synchronization of estrus have not progressed well. Therefore, using embryos at various developmental stages, ET was investigated in dogs from a beagle colony in which the ovulation days were close, as estimated by the progesterone level. Embryos were, recovered 8-11 days after ovulation (4-9 days after mating) by excising the oviducts and uteri (excision method) in 16 animals and by surgical flushing of the uteri at laparotomy (surgical method) in 3 animals. In 24 dogs with -4 to +2 days of difference in the timing of ovulation between donor and recipient dogs, 1-10 embryos at the 8-cell to blastocyst stages were transferred per animal. The mean embryo recovery rate by the excision method (97.1%) was significantly higher than that by the surgical method (42.5%) (p<0.01). Twelve (57.1%) of 21 animals with -1 to +2 days difference in ovulation day became pregnant after the transfer of 8-cell to blastocyst stage embryos. Although 3 dogs with -4 to -2 days of difference of ovulation day underwent ET of morula or compacted morula, none of these dogs became pregnant. The mean ratio of the number of newborns to the number of transferred embryos was only 51.9%. The mean duration of the period between ovulation and delivery in the pregnant recipients was 65.8 days, which tended to be longer than that in natural mating. These results demonstrate that pregnancy can be induced by ET at the 8-cell to blastocyst stage in dogs with -1 to +2 days difference in ovulation day.

Animals↗
PubMed1999

Absence of regular pulsatile LH secretion during pre- and post-implantation periods in sheep.

Two experiments were conducted to determine the patterns of LH secretion and to evaluate the LH responses to pulsatile administration of GnRH during early pregnancy in ewes. In experiment 1, pregnant ewes (n=16) were used to determine the concentration of LH in plasma of jugular blood samples collected every 15 min for 6h before (day 10 post-mating) and after (days 20 and 30 post-mating) implantation. In experiment 2, the pituitary LH responses to exogenous pulsatile administration of GnRH were examined on day 10 post-mating in 4 pregnant ewes. A small dose of GnRH (200 ng/ml saline) was injected (i.v.) every 3h and jugular blood samples were collected every 15 min for 12h beginning at the onset of GnRH administration and continuing through the 4th GnRH pulse. During the frequent-sample bleeding at any of the stages of pregnancy examined, LH concentrations oscillated in a pulsatile manner. However, pulsatile LH release occurred irregularly and infrequently. Overall mean LH concentrations, frequency and amplitude of LH pulses were not significantly different between any of the stages of pregnancy examined. Pulsatile administration of GnRH on day 10 post-mating induced regular pulses of LH. In conclusion, these data demonstrate that: (i) pulsatile LH secretion occurs irregularly during early pregnancy, and (ii) the absence of regular pulsatile LH release during early pregnancy is not attributed to a lack of pituitary responsiveness to GnRH.

Animals↗
PubMed1980

Effects of season, lactation and plane of nutrition on the reproductive performance and associated plasma LH and progesterone profiles in hormonally treated ewes.

Two experiments were designed to determine the effects of duration of lactation and plane of nutrition on the reproductive performance of Finn x Dorset Horn ewes mated at a hormonally induced oestrus 9 weeks after lambing. In Exp. 1, ewes were mated on 4 December or 19 March and lactation was terminated at 35 or 15 days before mating or 7 or 35 days after mating. The fertility of ewes lactating at the time of mating was reduced, particularly in ewes mated in March. This was not attributable to differences between lactating and non-lactating ewes for the incidence of oestrus, ovulation rate, litter size or the pattern of LH production. Indirect evidence based on progesterone profiles and returns to service suggest that reproductive failure was due to failure of fertilization and to embryonic death. In Exp. 2 ewes were mated on 1 July or 15 October. Lactation was terminated 15 days before or 7 days after mating and the ewes in each group were subjected to a high or low plane nutrition. Lactation depressed fertility in ewes mated in July but not in those mated in October. While the fertility of non-lactating ewes was independent of nutritional treatment, lactating ewes on a low plane and mated in July had a higher lambing rate than those on a high plane of nutrition. Nutritional effects on fertility appeared to be mediated through changes in milk production and reproductive failures were attributed to failure of fertilization and embryonic death. Seasonal and treatment effects on the incidence of oestrus and on ovulation rates, litter sizes and LH production were small and of little importance.

Animal Nutritional Physiological Phenomena↗
PubMed1980

Response of ewes to a single injection of an analogue of PGF-2 alpha given at different stages of the oestrous cycle.

Six groups of 4 ewes were given a single i.m. injection of 100 microgram ICI 80,996 on Days 3, 5, 8, 11, 14 or 16 of the oestrous cycle. On day 3 treatment was only partly effective in causing luteal regression, with only 2 of the 4 treated ewes returning to oestrus. Injection had no apparent effect when given on Day 16, at a time when luteal regression had already started naturally. However, treatment between Days 5 and 14 inclusive of the oestrous cycle evoked a rapid fall in progesterone concentrations to basal values of less than 0.5 ng/ml within 24 h with a high degree of synchrony in the return of oestrus (37.7 +/- 1.6 h) and the timing of the LH peak (45.3 +/- 3.2 h) after injection. We conclude that the corpus luteum of the ewe is responsive to ICI 80,996 only between Days 5 and 14 of the oestrous cycle.

Animals↗