Effects of repeated administration of hCG on follicular and luteal characteristics and serum progesterone concentrations in eCG-superovulated Sanjabi ewes

The objective of this study was to evaluate if treatment of equine chorionic gonadotrophin (eCG)-superovulated Sanjabi ewes with repeated administration of human chorionic gonadotropin (hCG) would increase the number of normal corpus luteum (CL) and serum progesterone concentrations and decrease the number of persistent follicles. The superovulated ewes were divided into four groups on day 0 (day of sponge removal); the ewes were treated by an intramuscular administration of 500?IU hCG on day 0 (Group I: n?=?10), on days 0 and 1 (Group II: n?=?10), or on days 0, 1, and 2 (Group III: n?=?10) and no treatment for control group (n?=?10). Blood samples were collected on days 0, 1, 2, 5, and 8 (day of slaughter), and serum progesterone concentrations were determined. According to progesterone concentrations, 50 (4/8) and 0?% of the ewes underwent premature luteal regression in the control group and the hCG groups, respectively. There were more CLs in Group III than in Group II and the control group. Ewes treated with hCG had a greater number of normal-looking CL. CL diameter was significantly greater in Group II and Group III than other groups. Total CL weight was significantly (P?<?0.05) higher in Group III than in Group I and the control group. Number of persistent follicle and persistent follicle diameter were lower in control group compared to the other groups. Eight days after sponge removal, serum progesterone concentration was significantly higher in Group III than in Group I and the control group. The present results indicate that repeated administration of hCG supported CL formation, increased serum progesterone concentration, and prevented premature luteal regression in eCG-superovulated Sanjabi ewes.     

Effect of megestrol acetate and progesterone on oestrous and fertility in cyclic Malpura and Chokla ewes

In Rajasthan, India megastrol acetate and progesterone were administered to ewes (25 Chokla, 25 Malpura, aged between 3 and 4) in November 1968. Each ewe received 50 mg of either megastrol acetate or progesterone. Administration was intravaginal or intramuscular. During treatment only 3 ewes (2 megastrol acetate-injected and 1 progesterone-injected ewes) came into heat; thus, the progestogens exerted an inhibiting effect. 76% and 88% of the megastrol acetate and progesterone ewes, respectively, exhibited heat within 96 hours of therapy's end. Breed showed no significant effect on occurrence of estrus after therapy. Release of estrus within 96 hours occurred in 91.3% and 74.0% of intravaginally and intramuscularly treated ewes, respectively. 17 (41.5%) of the 41 ewes inseminated at their synchronized estrus lambed as a result of breeding in that first cycle. Thus, questions arise as to efficiency of ovulation, fertilization, nidation, and lambing in the case of synchronized estrus by use of different progestogens. 75% of ewes showing typical fern pattern at insemination lambed. An antiseptic vaginal douche applied after withdrawal of the sponge used in iv administration might be responsible for increased posttreatment fertility in this group.     

The effect of progesterone impregnated sponges on fertility in anoestrous ewes

Progestagen impregnated sponges have been widely used for the induction and synchronization of oestrus in the ewe. We report here a study of the use of the natural hormone, progesterone, administered on sponges in order to induce oestrus in anoestrous ewes. A linear increase in fertility was observed when the progesterone dose was increased from 500 to 1000 mg. A similar quantity of progesterone (250 mg) was absorbed by the ewes regardless of the dose administered in the range 500 to 1200 mg. Sixty eight per cent lambing of treated ewes was achieved using sponges impregnated with 1000 mg progesterone. Optimum fertility appeared to be governed by adequate absorption of the hormone at a rapid initial rate, and this was ensured at the higher doses of progesterone.

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Kurzfassung Progestagen-getränkte Schwämme wurden zur Herbeiführung und Synchronisierung der Brunst bei Schafen weitgehend benutzt. Eine derartige Behandlung der Tiere kann zu einer geringeren Fruchtbarkeit, als sie unter natürlichen Zuchtbedingungen im Herbst besteht, führen. Die Wirkung von zunehmenden Dosen der verabreichten synthetisch hergestellten Progestagene auf die anschliessende Fruchtbarkeit der Schafe ist gut dokumentiert. Mehrere Verfasser haben den Restgehalt an SC-9880 gemessen, der auf den Schwämmen nach ihrer Entfernung von den Schafen, die zur Herbeiführung und Synchronisierung der Brunst behandelt worden waren, verblieb. Sie stellten eine lineare Zunahme der Frunchtbarkeit mit der verabreichten Dosis bei SC-9980 fest; bei höheren Dosen (30 bis 50 mg) wurde eine verlangsamte Progestagen-absorption von den Schwämmen beobachtet. Die Forscher berichteten, dass die Frucktbarkeit nicht-brünstiger Schafe bei Dosen von SC-9880 von über 30 mg bei 38 bis 67% Lammen liegen kann.Hier wird eine Untersuchung des natürlich vorkommenden Hormons Progesteron und seiner Verabreichung auf Schwämmen zur Herbeiführung der Fruchtbarkeit bei nicht-brünstigen Schafen beschrieben. Auch bei dieser Untersuchung wurde eine lineare Zunahme der Frucktbarkeit bei zunehmenden Dosen des verabreichten Progesterons beobachted. Ein Schwellenwert von Progesteron (250 mg) wurde von den Schafen unabhängig von der verabreichten Dosis im Bereich von 500 bis 1200 mg absorbiert. Bei den behandelten Schafen (mit 1000 mg imprägnierte Schwämme) wurde ein Ergebnis von 68% Lammen erzielt. Eine optimale Fruchtbarkeit wird anscheinend bei einer anfänglich schnellen, angemessenen Absorption des Hormons erzielt und diese Faktoren waren bei höheren Dosen von Progesteron gegeben.

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Resume On a largement utilisé la technique des éponges impregnées de progestagène pour induire et synchroniser l'oestrus chez les brebis. Un tel traitement peut entraîner un taux de fertilité inférieur à celui obtenu dans des conditions normales de reproduction en automne. L'effet de l'augmentation des doses de progestagène synthetique administrées sur la fertilité ultérieure des brebis a fait l'objet de nombreuses études. Plusieurs auteurs ont etudié les niveaux résiduels de SC-9880 sur les éponges après leur retrait des brebis qui avaient été traitées en vue de l'induction et de la synchronisation de l'oestrus. Ils ont constaté une progression linéaire de la fertilité en fonction des doses de SC-9880 administrées et un ralentissement de l'absorption du progestagène contenu les éponges aux doses les plus elevées utilisées (30 a 50 mg). Ces chercheurs ont signalé que la fertilité des brebis pendant l'anoestrus pouvait aller de 38 a 67% d'agnelage aux doses de SC-9880 supérieures à 30 mg.Le présent rapport a pour objet l'étude de l'hormone naturelle, la progestérone, administrée au moyen d'éponges pour induire l'oestrus chez les brebis en période l'anoestrus. Dans la présente étude, on a également observé une augmentation linéaire de la fertilité avec l'augmentation de la dose de progestérone administrée. On a constaté chez les brebis une valeur limite d'absorption de progestérone (250 mg), quelle que soit la dose administrée allant de 500 a 1200 mg. On a obtenu 68% d'agnelage chez les brebis traitées au moyen d'éponges impregnées de 1000 mg de progestérone. La fertilité optimale semble dépendre de l'absorption adéquate de l'hormone à un taux initial élevé, condition qui se trouve remplie en administrant des doses élevées de progestérone.

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Riassunto Le spugne impregnate di progesterone sono comunemente utilizzate per indurre e sincronizzare l'estro della pecora. Un simile procedimento rischia tuttavia di rendere l'animale meno fecondo rispetto alle condizioni di riproduzione naturale nella stagione autunnale. Gli effetti che dosi crescenti di preparati progestogeni producono sulla fecondità delle pecore sono del resto ampiamente documentati. Analizzando i residui di SC-9880 che restano sulle spugne rimosse dal corpo della pecora, diversi autori sono giunti alla conclusione che esiste un incremento lineare della fecondità se si somministrano le dosi sotto forma di SC-9880. La stessa indagine evidenzia inoltre un minore assorbimento di sostanza progestagena dalle spugne se si utilizzano dosi massime comprese fra 30 e 50 mg. I ricercatori affermano che le pecore in anestro hanno parti in una percentuale compresa fra il 38 e il 67% se ricevono dosi di SC-9880 superiori ai 30 mg.La presente ricerca riguarda la somministrazione mediante spugne di progesterone naturale per indurre l'estro nelle pecore in anestro. Essa dimostra che dosi crescenti di progesterone conducono ad un incremento lineare della fecondità. Esiste un tetto massimo di assorbimento del progesterone (250 mg) anche con dosi di somministrazione comprese fra i 500 e i 1200 mg. Il 68% dei parti delle pecore trattate si ha con spugne impregnate con 1000 mg di progesterone. La fecondità ottimale sembra dipendere da un adeguato ed inizialmente rapido assorbimento dell' ormone, ottenibile con dosi massime di somministrazione.

     

Effect of progesterone supplementation on pregnancy and embryo survival in ewes

Two hundred eighteen ewes were used in experiments 1) to develop a progesterone supplementation regimen capable of sustaining serum concentrations of progesterone at about 2.0 ng/ml for a period of 50 d (Exp. 1) and 2) to determine the effects of progesterone supplementation (d 6 to 50 after mating) on pregnancy and embryo survival rates in mated ewes (Exp. 2). In ovariectomized ewes in Exp. 1, s.c. administration of four cylindrical (9.5 x 60 mm) silastic implants, containing 20% (1.1 g) progesterone by weight, sustained mean serum concentrations of progesterone of 1.9 +/- .07 ng/ml compared with 1.03 +/- .05 ng/ml in ewes bearing two implants. In Exp. 2 each ewe (n = 159) was mated to two fertile rams at a spontaneous estrus (d 0) during mid-breeding season. Mean ovulation rate, determined on a subgroup of 46 ewes, was 1.45 +/- .05. On d 6, ewes were assigned randomly to control (two implants containing no progesterone) or progesterone-treated (four implants similar to those used in Exp. 1) groups. From d 7 to 50 after mating, progesterone concentrations in serum were greater (P less than .001) in progesterone-treated (four implants similar to those used in Exp. 1) groups. From d 7 to 50 after mating, progesterone concentrations in serum were greater (P less than .001) in progesterone-treated (3.50 +/- .06) than in control (2.65 +/- .05) ewes. Pregnancy rates (86% and 83%) and calculated embryo survival rates (77% and 78%) were similar (P greater than .05) for the control and progesterone-treated groups, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of progestagens on follicular growth and oocyte developmental competence in FSH-treated ewes

Previous research has reported evidence for negative effects of progestagens on follicular growth and oocyte competence. In the present study, negative effects of progestagens on follicular growth and oocyte developmental competence were assessed. During the breeding season, 20 Sarda ewes were treated with two doses of cloprostenol, 10 days apart, to assure the presence of a corpus luteum (CL). On day 5 after the second cloprostenol dose, 10 ewes were treated with a progestagen sponge while 10 females remained untreated. Starting on day 7 after the second cloprostenol dose, all the ewes were treated with 6 equal doses of 24 I.U. of FSH (Ovagen™, ICP, NZ), every 12 h. The number of follicles ≥2 mm in diameter increased (P < 0.0005) in all the ewes from 24 h before to 60 h after the first FSH dose (from 12.8 ± 1.1 to 23.4 ± 1.3 in treated and from 12 ± 0.6 to 22 ± 1.2 in untreated ewes, n.s.). There were no significant differences in follicle dynamics between groups, but concentrations of estradiol in control ewes were higher than in the progestagen group (P < 0.05). Twelve hours after the last FSH dose, oocytes were collected by ovum pick-up. Recovery rates were lower for progestagen-treated ewes (71.1 versus 83%; P < 0.001). After IVP procedure, cleavage rate was also lower in the progestagen group (39.1 versus 82.6%; P < 0.001). Furthermore, blastocysts output revealed that oocyte developmental competence was lower in progestagen group (17.3 versus 30.4%; P = 0.245), although differences were not significant. These results suggest deleterious effects from progestagen on oocyte developmental competence and set the basis for new protocols for in vitro embryo production.     

Effects of exogenous estradiol and progesterone on plasma concentrations of leptin in ewes in non-breeding season

Estradiol and progesterone may play a role in controlling leptin secretion by utilizing their receptors in adipocytes and the genomic mechanisms of the leptin gene. This study was conducted to evaluate the effects of exogenous sex steroids on the blood leptin concentrations in ewes in the non-breeding season. Multiparous ewes were fed to maintenance level for their live weights. Blood samples were collected at 12-h intervals from Days -3 to -1 to determine the basal leptin levels (pre-injection period). From Day 0 to Day 5 (injection period), blood sampling continued at 12-h intervals, and the ewes were injected intramuscularly at 24-h intervals with oil, 50 mg progesterone in oil, 1 mg of estradiol in oil, or both steroids in oil. Leptin was measured using a sensitive and specific radioimmunoassay based on recombinant bovine leptin. Overall, plasma concentrations of leptin were not affected by any of the steroid treatments, and there were no differences in the value of leptin between the pre-injection and injection periods among the 4 groups. Therefore, the exogenous estrogen and progesterone used in this study do not have a strong effect on the blood leptin concentrations of ewes in the non-breeding season.     

Effect of charcoal-extracted porcine follicular fluid and 17 beta-estradiol on follicular growth and plasma gonadotropins in gilts fed a progesterone agonist, altrenogest

Thirty-four gilts in two experiments were fed altrenogest for 18 d to block spontaneous growth of ovulatory follicles after luteolysis. They were injected with estradiol or charcoal-extracted porcine follicular fluid (pFF) to determine 1) whether gonadotropin secretion could be depressed and 2) whether exposure to reduced levels of gonadotropins would result in decreased numbers of medium follicles (3 to 6 mm in diameter). Gilts in Exp. 1 received treatments in a 2 X 2 X 2 factorial arrangement starting 48 h before the last feeding of altrenogest. Corn oil or estradiol (2 micrograms/kg body weight), 5 ml of charcoal-extracted porcine serum (pS) or pFF were injected im four times at 8-h intervals and gilts were sacrificed 24 or 96 h after last feeding of altrenogest. In Exp. 2, gilts received one of four treatments consisting of 1) pS, injected iv nine times at 8-h intervals starting 48 h before the last feeding of altrenogest; 2) pFF, with injection protocol the same as for pS; 3) estradiol injected im three times and 4) four times at 8-h intervals starting 0 and 24 h, respectively, before the last feeding of altrenogest. Compared with pS or corn oil, estradiol increased (P less than .001) plasma estrogen and decreased (P less than .05) plasma luteinizing hormone (LH) without a significant effect on plasma follicle stimulating hormone (FSH). Estradiol, compared with corn oil, decreased (P less than .01) the number of medium follicles from 24.8 to 0/gilt and decreased (P less than .05) the weight of ovarian follicular fluid from 4.2 to 2.1 g/gilt at 72 h after the first injection. Five milliliters of pFF had no significant effect on plasma gonadotropins or number of medium follicles. However, 20 ml of pFF, compared with pS, decreased (P less than .05) plasma FSH from 45 ng/ml to 9 ng/ml 32 h after the first injection, had no effect on plasma LH, decreased (P less than .01) the number of medium follicles from 29.2 to 2.2/gilt and decreased (P less than .01) follicular fluid weight from 3.9 to 1.6 g/gilt by 72 h after the first injection. These results indicate that estradiol or a non-steroidal component of follicular origin can decrease secretion of gonadotropins and suppress recruitment of medium follicles in the pig.     

Gonadotropin concentrations, follicular development, and luteal function in pituitary stalk-transfected ewes treated with bovine follicular fluid.

Two experiments, each arranged as a 2 x 2 factorial, were conducted in ewes to examine direct effects of bovine follicular fluid (bFF) on follicular development and luteal function and to further characterize follicular development and luteal function after pituitary stalk transection (SS). In Exp. 1, ewes were sham-operated or SS on d 6 of an estrous cycle and received 5 ml of saline or bFF three times daily on d 5 through 11 of the same cycle. In Exp. 2, all ewes were SS on d 6 of an estrous cycle and treated with saline or bFF three times daily on d 5 through 11 and with ovine FSH (60 micrograms; NIADDK-oFSH-16) or saline (1.2 ml) from d 7 to 11. In Exp. 2, ewes were ovariectomized on d 11 to assess effects of treatments on follicular development and luteal function. In both experiments, concentrations (ng/ml) of FSH on d 7 were suppressed (P less than or equal to .005) by bFF compared with saline (.50 +/- .17 vs 1.63 +/- .15) and remained suppressed (P less than or equal to .005) through d 11 (.46 +/- .12 vs 1.54 +/- .12). Replacement therapy (oFSH) restored concentrations of FSH. Concentrations of LH were not affected by bFF but were elevated (P less than or equal to .05) 1 d after SS (d 7; .88 +/- .09 vs .56 +/- .09) and remained elevated (P less than or equal to .05; 1.31 +/- .20 vs .65 +/- .11) from d 6 through 11. Concentrations of progesterone were unaffected by SS.(ABSTRACT TRUNCATED AT 250 WORDS)     

Periovulatory changes in peripheral plasma progesterone and estrogen concentrations in the mare.

Concentrations of progesterone and estrogen were measured in peripheral blood plasma samples from mares around the time of ovulation. Samples were collected every 2 hours from 36 hours before, to 26 hours after, ovulation and assayed by radioimmunoassay. Progesterone concentrations were between 60 and 100 pg/ml for the period 24 hours before ovulation through 8 hours after ovulation. By 10 hours after ovulation, concentrations increased to 140 pg/ml and, by 26 hours after ovulation, reached 346 pg/ml. Plasma estrogen concentrations did not change significantly throughout the same period.     

Effect of feeding flax or linseed meal on progesterone clearance rate in ovariectomized ewes

Ovariectomized ewes (n=22; 68.76+/-2.34 kg initial body weight; 2.9+/-0.1 initial body condition score) were individually fed one of three diets: (1) control (phytoestrogen-free; n=7), (2) flax containing diet (n=8), or (3) linseed meal (LSM) containing diet (n=7) to investigate the rate of progesterone (P4) clearance. On day 20 of feeding (day 0=initiation of treatment), a P4 releasing device (CIDR) was placed in the vagina and jugular blood samples were obtained prior to CIDR insertion and 15, 30, 60, and 120 min following CIDR insertion. Further, blood samples were obtained daily between days 21 and 24. On day 25, blood samples were retrieved prior to CIDR removal and 2, 5, 10, 15, 30, 60, 120, and 360 min following CIDR removal. There was no difference in initial or final body weight or body condition score and there were no time by diet interactions on P4 clearance. The fractional rate of P4 uptake measured prior to CIDR insertion through day 4 following insertion tended to be greater (P=0.07) in LSM fed ewes (508.75+/-71.37%/min) compared to flax (295.39+/-66.76%/min) and control fed (287.54+/-71.37%/min) ewes. Diet tended (P=0.10) to influence P4 clearance rate when measured from prior to CIDR removal through 120 min following CIDR removal with LSM fed ewes having a greater (1.26+/-0.2) fractional rate constant than flax (0.929+/-0.09) and control fed (0.922+/-0.09) ewes. Flax fed ewes also had more (P<0.01) omega-3 fatty acids and total fatty acids in plasma. Reports of increased pregnancy rates in dairy cows fed flax may relate to P4 metabolism.     

Effect of system of lamb rearing and season on early post‐partum fertility of ewes and growth performance of lambs in Katahdin sheep

The effect of season (S), lamb rearing system (RT) and grain supplementation (GS) on post‐partum fertility in Katahdin ewes and growth in Katahdin lambs was evaluated. Katahdin ewes were bred to lamb in fall (n = 36) or spring (n = 56) and at approximately 2.5 months post‐partum were randomly assigned to be permanently separated or to continue to suckle their lambs for an additional 3 months. All ewes were joined with rams following treatment to synchronize oestrus. Weaned (W, n = 84) and continuously suckled lambs (CSK, n = 88) were fed forage only (n = 84; hay and pasture for fall‐ and spring‐born lambs respectively) or were supplemented (n = 88; 18% crude protein ration ad libitum) and all weighed biweekly. Ewes rebred in the fall had a shorter ram introduction to lambing interval (p < 0.05), higher prolificacy (p = 0.001) and higher lambing rates (p = 0.02); however, the proportion of ewes lambing was not affected by season. The first service lambing rate was lower in ewes continuously suckling lambs in the spring, but not in the fall breeding season (S × RT, p = 0.03). Lambs that continuously suckled their dams and were supplemented grew quicker and gained more (p < 0.001) than their weaned and unsupplemented counterparts. The effect of CSK on growth rate of lambs was greater in the spring (RT × S; p = 0.05), and the effect of supplementation on growth rate of lambs was greater in the fall (GS × S; p < 0.0001). In conclusion, Katahdin lambs achieved higher weight gains from continuous suckling and grain supplementation. Moreover, Katahdin ewes are capable of early rebreeding post‐partum while suckling their lambs, which makes them suited for use in accelerated lambing programmes.     

Effect of dietary intake on concentrations of insulin-like growth factor-I in plasma and follicular fluid, and ovarian function in heifers.

The objective of this study was to determine if alterations in dietary intake of heifers can influence IGF-I concentrations in plasma and(or) follicular fluid (FFL), size of follicles, and steroid concentrations in FFL (as an indicator of steroidogenic capacity). Cyclic heifers [n = 23; mean +/- SE body weight (BW) = 373 +/- 7 kg] were individually fed for 10 weeks either: a) 1.8% of BW in dry matter (DM) per d (GAIN; n = 7), b) 1.1% of BW in DM per d (MAINT; n = 8) or c) 0.7% of BW in DM per d (LOSE; n = 8). After 10 wk of treatment, heifers were ovariectomized 36-40 hr after the second injection of prostaglandin F2 alpha analog (2 injections 11 d apart), and plasma and ovaries were collected. Heifers weighed 444 +/- 13,387 +/- 8 and 349 +/- 9 kg in the GAIN, MAINT and LOSE groups, respectively, at time of ovariectomy. Mean diameter of follicles greater than or equal to 10 mm was greater (P less than .05) for GAIN (15.6 mm) than for MAINT (11.0 mm) or LOSE (12.5 mm) heifers. Numbers of follicles and concentrations of IGF-I in plasma and FFL did not differ (P greater than .20) between LOSE, MAINT and GAIN heifers. Progesterone concentrations were greater (P less than .05) in small and medium follicles of GAIN than MAINT or LOSE heifers, but were unaffected by diet in large follicles. Estradiol concentrations in FFL in small, medium and large follicles were unaffected (P greater than .20) by dietary treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of the preovulatory LH surge on bovine follicular progesterone receptor mRNA expression

A growing body of evidence indicates that intrafollicular progesterone receptor signaling pathways are obligatory for follicle rupture. However, the intrafollicular localization and regulation of progesterone receptor expression during the periovulatory period in cattle are not known. In this study, we determined the effect of the preovulatory gonadotropin surge on localization and expression of progesterone receptor mRNA in bovine periovulatory follicular and luteal tissue. Ovaries containing preovulatory follicles or new corpora lutea (CL) were collected at approximately 0, 6, 12, 18, 24 (preovulatory follicles) and 48 h (CL) after a GnRH-induced LH surge (n=5-8 per timepoint). Expression of progesterone receptor mRNA was detected in periovulatory follicular and luteal tissue at all timepoints examined. Relative levels of progesterone receptor mRNA were dramatically upregulated within 6h after the LH surge compared to all other time points (P<0.0001). In situ hybridization analysis revealed that the significant increase in progesterone receptor mRNA expression was localized to the granulosal layer of preovulatory follicles. Our results indicate that progesterone receptor mRNA expression is upregulated specifically in the granulosal layer of bovine preovulatory follicles following the LH surge. Progesterone receptor signaling pathways may help mediate the effects of the preovulatory LH surge on follicle rupture in cattle.