Fluorogestone Acetate Research Articles

Control of oestrus in ewe lambs and yearling ewes with medroxyprogesterone acetate and fluorogestone acetate

Two experiments were conducted in a large flock of Berrichon purebred and Romanov × Berrichon F 1 crossbred ewes. In experiment 1, 157 ewe lambs were placed in six groups according to season of mating and maternal breed. Within each group equal numbers of females were treated with either medroxyprogesterone acetate (MAP) or fluorogestone acetate (FGA)-impregnated sponges for 14 days; dosage of PMSG at the time of sponge removal was 500 and 300 I.U. respectively for pure and crossbred. In experiment 2, 111 dry yearling ewes of the Berrichon breed were involved, of which 35, 51 and 25 had either a short lambing to treatment interval (approximately 3 months), a long lambing to treatment interval (approximately 6 months), or were primiparous or nulliparous. They were also treated either with MAP or FGA. The conception rates were extremely high (overall near 86%) in ewe lambs and not significantly affected by seasons or breeds or treatments. Prolificacy and number of lambs per ewe mated were higher in the F 1 crossbred group than in pure Berrichon females (respectively 1.91 vs. 1.34 lambs/mated ewe). No significant difference between the two progestagens could be observed for any of the productivity criteria. Fertility was equally satisfactory in yearlings (overall near 85%) irrespective of the interval between lambing and mating. However, the fertility of the nulliparous ewes (those that failed to conceive as ewe lambs) was significantly lower (72%). The number of lambs per ewe mated was 1.78 in yearlings with a 6-month interval from lambing to mating but was not significantly different from the numbers recorded in the other two groups (1.37 and 1.36). As in experiment 1, there was no difference in the results obtained after either of the two progestagen treatments. In conclusion, progestagen treatment has been shown in both ewe lambs and yearlings to be a very effective means of increasing lamb production in large flocks. This was achieved in ewe lambs regardless of the season and, in dry yearling ewes, regardless of the interval from lambing to mating in the anoestrous season.

REPRODUCTIVE PERFORMANCE OF HORMONALLY TREATED SHEEP MAINTAINED YEAR-ROUND IN A CONTROLLED-LIGHT ENVIRONMENT

Six experiments were conducted on hormonally treated ewes maintained year-round in a controlled-light environment in a breeding program designed to produce three lamb crops in 2 yr. Various combinations of fluorogestone acetate (FGA), prostaglandin F2α (PGF2α) and pregnant mares' serum gonadotrophin (PMSG) were used to synchronize estrus in the ewes. There were no significant differences (P > 0.05) in fertility between FGA- and PGF2α-treated ewes when the ewes were having cyclic ovarian activity (cycling) at the time of treatment, i.e. in January and May in our system. Among ewes in the constant day-length lighting regime, fertility was lower in September than in January or May. Prolificacy ranged from 1.7 to 2.0 in the six experiments. Fecundity, a measure of the overall productivity, followed a similar pattern to fertility and was not significantly (P > 0.05) affected by the various treatments. These findings demonstrated the feasibility of maintaining a controlled 8-mo breeding program for sheep maintained year-round in a controlled-light environment. Key words: Reproduction in sheep, controlled light, hormone treatment effects.

APPLICATION OF CONTROLLED REPRODUCTION TO SHEEP FLOCKS IN NEWFOUNDLAND

A 3-yr study demonstrates that commercially acceptable reproductive performance can be achieved in breeding sheep following the application of a fluorogestone-acetate- (FGA-) impregnated intravaginal sponge and pregnant mare's serum gonadotrophin (PMSG) treatment to induce a synchronized estrus under field conditions. Overall fertility, prolificacy and fecundity levels of 76%, 1.92 and 148%, respectively, resulted from breeding at the synchronized estrus, and 94%, 1.86 and 175%, respectively, due to breeding at the synchronized and subsequent estruses in the breeding (fall) season. In the nonbreeding (spring) season, these responses were 51%, 1.73 and 88%, respectively, at the synchronized estrus, and 63%, 1.61 and 109%, respectively, due to breeding at the synchronized and subsequent estruses. Significant farm-to-farm variation was observed with reproductive performance ranging from 77 to 100% for fertility, 1.45 to 2.74 for prolificacy, and 134 to 274% for fecundity in the estrous season. There were no significant differences among farms after synchronization and breeding during the anestrous season. Key words: Sheep, synchronization, fluorogestone acetate, pregnant mare's serum gonadotrophin, season, farm flocks.

EFFECT OF DOSE OF PREGNANT MARES' SERUM GONADOTROPHIN ON THE REPRODUCTIVE PERFORMANCE OF EWES SYNCHRONIZED FOR ESTRUS AND HOUSED IN TOTAL CONFINEMENT

Ewes housed indoors year round were treated with 40 mg of fluorogestone acetate followed by 0, 250, 500 or 750 IU pregnant mares' serum gonadotrophin (PMSG). PMSG did not enhance fertility, prolificacy or fecundity in ewes bred at the synchronized estrus. Key words: Sheep, PMSG, synchronization, fertility, prolificacy, fecundity

Effect of PMSG on the reproductive performance of totally confined ewes bred at synchronized estrus

The reproductive performance (fertility, prolificacy and fecundity of totally confined sheep in a controlled breeding program at the Animal Research Centre (ARC) was analyzed to evaluate the effect of pregnant mares' serum gonadotrophin (PMSG) on ewes synchronized for estrus with fluorogestone acetate (FGA). PMSG did not significantly enhance reproductive performance. Fertility for ewes receiving 500 IU PMSG was 57% and for ewes not receiving PMSG it was 47%. Corresponding values for prolificacy were 2.4 and 2.2, and for fecundity, 144 and 103%. The reproductive performance was not affected by any of the other factors (flock, strain, lighting regime, ram age or reproductive status of the ewe) indigenous to the controlled breeding program for sheep housed in total confinement.

COMPARISON OF NATURAL MATING AND ARTIFICIAL INSEMINATION ON REPRODUCTIVE PERFORMANCE OF THREE STRAINS OF SHEEP HOUSED IN TOTAL CONFINEMENT

The reproductive performance (fertility, prolificacy and fecundity) of confined sheep was measured following natural mating or artificial insemination (AI) with 0.1 mL of unextended semen collected by artificial vagina or by electroejaculation. The estrous cycles of the ewes were synchronized in late summer using intravaginal sponges impregnated with fluorogestone acetate. Pregnant mares' serum gonadotrophin (PMSG) was administered intramuscularly to approximately half of the ewes. There was no significant difference in the reproductive performance of ewes bred by natural mating (45%) or AI (30%) or between the two methods of semen collection (30 vs. 29%). Fertility was greater (P < 0.05) in ewes treated with PMSG (33 vs. 11%) mainly because of a tendency for higher fertility in ewes bred by AI. PMSG also significantly (P < 0.01) increased prolificacy and fecundity, 1.8 vs. 1.5 and 58 vs. 16%, respectively.

On the inhibitory effect of some steroids on spermatogenesis in adult rainbow trout (Salmo gairdneri)

To test the antifertility effect of various steroids, fish were fed a diet containing steroids at two stages of the reproductive cycle: during spermatogenesis (June to November, experiment A) and during spermiation (November to February, experiment B). The fish in experiment A were given testosterone (T), methyltestosterone (MT), estradiol-17β (E2), hexestrol (H), progesterone (Pg), and FGA (Fluorogestone acetate) at doses of 0.05 and (or) 0.5 mg/kg of food. In experiment B, T, MT, and E2 were given at a dose of 0.5 mg/kg of food. The fish received a daily ration amounting to 1% of their body weight. In experiment A, inhibition of testicular growth was total with 0.5 mg MT and 0.5 mg E2 and partial with 0.5 mg T/kg of food. In these groups, there was no noticeable change in plasma gonadotropin (GTH) compared with the controls, except that the GTH rise observed in the other groups in September was prevented. This suggests that steroids act directly at the level of the gonad. In experiment B, no noticeable regression of the gonad occurred after steroid treatment. A big GTH rise was seen in the E2-treated group, but this was not followed by stimulation of spermiation. The total amount of sperm (50%) and spermatozoa collected during the experiment tended to be lower in the steroid-treated fish than in the controls. Spermatozoal fertilizing ability was significantly decreased (P < 0.005) by the testosterone treatment.

Effects of prostaglandin F2 alpha and pregnant mares' serum gonadotropin (PMSG) on the reproductive performance of fluorogestone acetate PMSG-treated ewes.

Two experiments were conducted to examine the effect of prostaglandin F2 alpha (PGF2 alpha) and pregnant mares' serum gonadotropin (PMSG) on the reproductive performance (fertility, prolificacy and fecundity) of ewes previously treated with fluorogestone acetate (FGA) and PMSG. In the first experiment, 29 ewes were synchronized for estrus with FGA and PMSG but not bred at the postsynchronization estrus. On day 10 of the first post-synchronization estrous cycle, they were injected IM with 15 mg PGF2 alpha and 500 IU PMSG and exposed to experienced, fertile, raddled rams. Twenty-four of the 29 ewes (83%) had viable fetuses 9 weeks after the PGF2 alpha-PMSG treatment. In the second experiment, 64 ewes were treated with FGA-PMSG, and 33 were exposed to fertile, raddled rams at the synchronized estrus. A second group of 31 ewes was not bred at the synchronized estrus, but on day 12 of the postsynchronized estrous cycle, they were injected IM with 15 mg PGF2 alpha and 500 IU PMSG and exposed to fertile, raddled rams. Sixty-six percent of the 33 ewes lambed in the FGA-PMSG-treated group and 60% of the 31 ewes lambed in the PGF2 alpha-PMSG-treated group. Differences in reproductive performance between these two treatment groups were not statistically significant. The results suggest that the PGF2 alpha-PMSG treatment combination does not adversely affect reproductive performance of ewes.

COMPARISON OF TWO METHODS OF SYNCHRONIZING ESTRUS AND SUBSEQUENT LAMBING IN A COMMERCIAL SHEEP FLOCK

Ewes of a commercial sheep flock were treated with either two 15-mg intramuscular injections of prostaglandin F2α (PGF2α), 11 days apart, or vaginal sponges impregnated with 40 mg fluorogestone acetate (FGA) in place for 12 days to compare the two methods of synchronization of estrus. Each treatment was imposed on two subgroups of 36 ewes commencing on various days of an 8-day period so that maximum available ram power could be used. A third group of 38 ewes was not treated (controls). At lambing time, the duration of lambing and distribution of lambings for the treated and control ewes were compared. There was no significant difference (P > 0.05) in the proportions of ewes responding over a 6-day period to the PGF2α (84%) and FGA (89%) treatments. Similarly, there was no difference (P > 0.05) in fertility between the two treatments, PGF2α (63%) and FGA (78%). The 38 control ewes were bred over a 15-day period and 60% lambed to the first service. This was not different (P > 0.05) from the combined fertility (67%) of ewes responding (synchronized) to either treatment. All of the pregnant ewes that had been synchronized for estrus by either treatment lambed over a 22-day period with (83%) lambing within an 8-day period. The 21 control ewes pregnant to a first service lambed over a 19-day period; however, only 67% lambed in the above corresponding 8-day period. Prolificacy did not differ between the two treatments (both were 1.3), or between the treated (1.3) and non-treated ewes (1.4). PGF2α can be used effectively as an alternative to FGA for synchronization of estrus in ewes during the breeding season. Even though the synchronization of estrus was staggered over an 8-day period, the resulting condensation of the lambing interval of the treated ewes proved to be beneficial in the commercial sheep operation.

COMPARISON OF ARTIFICIAL INSEMINATION AND NATURAL MATING ON REPRODUCTIVE PERFORMANCE OF FIVE STRAINS OF SHEEP DURING THE ANESTROUS SEASON IN AN INTENSIVE SYSTEM

Synchronized estrus and ovulation were induced during the anestrous season (April–May 1974) in 373 ewes of three synthetic (one sire and two dam) strains and two unselected (Suffolk and Finnish Landrace) purebred strains by treatment with 30 mg fluorogestone acetate (FGA) impregnated in polyurethane intravaginal sponges for 12 days. Following sponge removal each ewe received 500 IU pregnant mares’ serum gonadotrophin (PMSG) IM. Of these, 167 were bred by artificial insemination (AI) at 48 and 60 h post sponge removal with 0.2 ml raw unextended semen collected by electroejaculation (EE). Five days after AI, ewes were exposed to a follow up ram for 16 days for subsequent mating if a second estrus occurred. The remaining 206 were exposed to rams for a period of 22 days for natural mating. Blood samples were collected from 69 ewes, 9, 19 and 27 days post sponge removal and analyzed for progesterone to ascertain if corpora lutea were formed and whether the ewes recycled. The age of ram by mating method interaction significantly affected both fertility and fecundity mainly because some of the younger rams lacked libido and experience for natural mating. There were no significant differences in prolificacy due to any of the main effects tested. Among the 69 ewes examined for progesterone levels, 93% had formed corpora lutea after hormone treatment and 16% recycled. Only 16 of the 255 ewes that did not conceive to the synchronized estrus lambed to the subsequent estrus.

Peripheral plasma levels of progesterone in goats treated with fluorogestone acetate and prostaglandin F2 α during the estrous cycle

Intravaginal pessaries impregnated with 20 mg fluorogestone acetate (FGA) were inserted into fifteen does at various intervals after the end of estrus. After resumption of cyclical activity following withdrawal of the intravaginal pessaries, the does were divided into six groups and treated with prostaglandin F2 α. Each doe received 15 mg Prostaglandin F2 α administered intramusuclarly 2, 4, 6, 12, 14 or 16 days after the end of estrus. The animals were bred naturally on the first estrus following prostaglandin treatment. Jugular blood samples were collected from each doe throughout the experimental period. The plasma samples were assayed for progesterone. Intravaginal fluorogestone acetate treatment in does had no effect on the function of the corpus luteum, however, overt estrus was postponed during treatment and for a few days after removal of the pessaries. Prostaglandin injection into does, 4, 6, 12, 14 or 16 days after the end of estrus induced luteolysis and subsequent ovulatory estrus within 2 to 3 days. Fertility at PGF2 α induced estrus in these does was 77%. Prostaglandin treatment two days after the end of estrus had no effect on the corpus luteum function. It is concluded that prostaglandin is luteolytic when administered into does anytime beyond four days after the end of estrus.

Sequential administration of cronolone and prostaglandin F2α for estrus synchronization in goats

Fifteen does received intravaginal pessaries impregnated with 20 mg fluorogestone acetate (Cronolone) at various times after the end of estrus for a period of fourteen days. The does were then treated on days 2, 4, 5, 12, or 16 after onset of estrus following the progestin treatment, with 15 mg of prostaglandin F2 α (Lutalyse) injected intramuscularly. Seventy three percent of the does showed estrus within 2 days after withdrawal of progestin treatment. Ten out of 11 does treated with prostaglandins 4 to 16 days after the end of estrus exhibited estrus within 44 to 72 hours after treatment. Breeding following the use of prostaglandin in these does resulted in a high pregnancy rate. It is concluded that a sequential use of progestin and prostaglandin may be a useful method for achieving estrus synchronization associated with high fertility in does.

Oestradiol-17beta, progesterone, FSH and LH in prepubertal calves induced to superovulate.

Fluorogestone acetate (vaginal sponge for 4 days) and PMSG (i.m. injection at the time of sponge insertion) treatment was administered to seven 3-month-old calves to induce superovulation. Samples of peripheral plasma were taken every 4 h during treatment (4 days) and then every 2 h for 7 days. FSH, LH, oestradiol and progesterone were measured by radioimmunoassays. In all calves oestradiol concentrations increased 24 h after PMSG injection and reached the highest levels (41-502 pg/ml) during the preovulatory surge of both gonadotropins. The surge of LH and FSH occurred from 12 to 22 h after cessation of treatment. The maximum levels of LH and FSH were 11-72 ng/ml and 23-40 ng/ml respectively and occurred within 4 h of each other. Between 40 and 68 h after the LH peak the concentrations of progesterone began to increase from basal values, reaching 24.0-101.7 ng/ml when the animals were killed. A quantitative relationship was found between plasma oestradiol concentration and the numbers of ovulating follicles. Progesterone levels seemed to be related to the numbers of corpora lutea and also to the numbers of unovulated follicles. Gonadotrophin output was not quantitatively related to ovarian activity or to steroid secretion.

Induction of lambing every eight months in two breeds of sheep by light control with or without hormonal treatment

SUMMARYSuffolk and Rambouillet female sheep (ewes) were kept in pens where daylight was gradually reduced and were treated, or not treated, with hormones to obtain four lambing cycles in 2·5 years. Oestrus in May, June and July was induced more easily (P<0·01) in Rambouillet than the Suffolk ewes. The advantage of higher conception rates in the Rambouillet ewes during anoestrus was offset by the higher prolificacy rates in the Suffolk in the other three lambing cycles. On average, each breed produced 128 lambs per 100 ewes exposed per lambing cycle. This corresponds to 5·1 lambs per ewe in four lambings, which is equivalent to 2·04 lambs per ewe per year. Under the conditions of the experiment, the addition of Syncro-Mate pessaries (20 mg fluorogestone acetate) and pregnant mare serum gonadotrophin (PMSG, 5 ml/ewe, 50 IU/ml) to the treatment of reduced daylight did not affect the ovulation or conception rates.

Influence of the presence of rams on the timing of ovulation and discharge of LH in ewes.

The influence of the presence of the male on the ovulation process was investigated in ewes after oestrus control by progestagens (intravaginal fluorogestone acetate) and PMSG. Permanent contact with the rams throughout oestrus accelerates the ovulation and the appearance of the LH surge. The results suggest that the action of the presence of the male on ovulation is mediated by way of the ovulatory surge of LH.

Influence of the presence of rams on the timing of ovulation and discharge of LH in ewes

The influence of the presence of the male on the ovulation process was investigated in ewes after oestrus control by progestagens (intravaginal fluorogestone acetate) and PMSG. Permanent contact with the rams throughout oestrus accelerates the ovulation and the appearance of the LH surge. The results suggest that the action of the presence of the male on ovulation is mediated by way of the ovulatory surge of LH.

Influence of fluorogestone acetate (FGA) on hypothalamo-hypophysial activity in anoestrous dry and lactating ewes.

Influence of fluorogestone acetate (FGA) on hypothalamo-hypophysial activity in anoestrous dry and lactating ewes.

Action in vitro du facteur hypothalamique de libération de l'hormone lutéinisante (LRF) sur l'antéhypophyse d'agnelle : I. Cinétique de l'excrétion de l'hormone lutéinisante (LH)

The in vitro release of luteinizing hormone (LH) from ewe pituitary slices under the action of partially and highly purified preparations of LH-releasing factor (LRF) has been studied. The pretreatment of ovariectomized ewes with a synthetic progestogen, fluorogestone acetate (FGA), increased the sensitivity of the response of the tissues to LRF. Kinetics of the release of LH from pituitary slices incubated with constant doses of LRF has been studied in two different ways. The following results were obtained: (1) if the incubation medium is not changed during the incubation process, the release of LH occurs at a constant rate for a 4–5-hr period and then diminishes, in spite of the addition of a further amount of LRF; (2) if the incubation medium is replaced by a new medium of the same composition, once or several times during the incubation process, the release of LH may occur for at least 7 hr. The addition of a highly purified ovine LH into the medium at the beginning of the incubation process does not seem to affect the release of LH from pituitary slices as induced with LRF. An extract from sheep brain cortex induces the release of a small amount of LH under the same experimental conditions. Using a micromethod, labeled LH was isolated from the pituitary tissues incubated in a medium containing LRF and labeled amino acids. This LH was obtained with a good yield and an acceptable biological potency, but the rate of incorporation of the radioactivity was relatively poor.

Action in vitro du facteur hypothalamique de libération de l'hormone lutéinisante (LRF) sur l'antéhypophyse d'agnelle : II. Etude ultrastructurale des tissus incubés

The ultrastructural evolution of ewe-lamb pituitary slices incubated as function of time (30 min, 60 min, 90 min, 2 hr, 3 hr, 4 hr, 8 hr and 24 hr) was studied in absence or presence of a purified hypothalamic luteinizing hormone releasing factor (LRF) and in one case in the presence of a brain cortex extract. High resolution autoradiography was utilized in order to appreciate the protein synthesis ability of the cells. Anterior pituitaries were obtained from ovariectomized ewe-lambs pretreated either with fluorogestone acetate (FGA) or with progesterone and estradiol benzoate. LH, FSH, and prolactin cells were identified at electron microscope level. All these cells were stimulated by castration. The treatment by progestogen was followed by storage of granulations in Lh cells and by an increased activity of prolactin cells. In the absence of brain cortex extract or of LRF, particularly beyond 4-hr incubation periods, all pituitary cell types underwent a progressive necrosis with the exception of prolactin cells, which maintained an intense secretory activity. Before the 4-hr period the release of granulations in LH cells followed a normal process. Brain cortical extract added during the first 90 min of incubation improved preservation of tissues. LRF did not prevent necrosis of most of the pituitary cells and did not inhibit the intense secretory activity of prolactin cells. LRF selectively stimulated the survival and secretory activity of LH cells. To an increasing rate, and already after 30 min, this stimulation affected all the intracellular organites implied in the whole secretory process: ergastoplasm, Golgi zone, granulations. Moreover. LRF exerted a morphogenetic action as shown by an increase of cytoplasm area and of intracellular membrane system.

Reproductive performance of ewes in an early-weaning, controlled-breeding program.

A total of 48 crossbred ewes was used to study reproductive performance in a four consecutive lamb crop program which included early weaning (2 months) and subsequent breeding control treatments. Hormonal treatments included the use of fluorogestone acetate impregnated pessaries which were intravaginally placed and equine gonadotropin injections. Removal of the impregnated pessaries resulted in estrous activity within 2 to 3 days in the majority of both cyclic and anestrous ewes. In regard to total reproductive performance (breeding and lambing), a procedure involving utilization of the impregnated pessaries during two spaced periods was the most consistently effective procedure tested. An exception to this was in one study where treatment was initiated during anestrus in which an injection of equine gonadotropin given at the time of pessary withdrawal was the most effective treatment.