Ovine estrus synchronization and superovulation using norgestomet B and follicle stimulating hormone-pituitary

Finewooled Rambouillet range ewes were used in a study to determine the feasibility of using a progesterone ear implant to synchronize estrus. In addition, some of the ewes were further treated with injections of follicle stimulating hormone-pituitary (FSH-P) to induce superovulation. Five days following estrus detection and breeding, FSH-P-treated ewes were laparotomized and surgically flushed to recover embryos. The number of corpora lutea (CL), the total number of embryos and the number of transferable embryos recovered were recorded along with the number and size of follicles present on both ovaries. Ewes synchronized as recipients were laparotomized for surgical transfer of embryos 5 d following estrus. The number of CL and follicles were recorded. Response to superovulation by FSH-P did not differ (P>0.05) between age groups of ewes when the number of CL present was counted. However, the total number of embryos flushed and good embryos was lower (P<0.05) among the oldest (7 yr) ewes. The number of follicles present showed little variation between age groups. Recipient ewes (No FSH-P) were similar in the number of CL with 6-yr-old ewes, having fewer (P>0.05) CL, than 3-, 4- or 7-yr-old ewes. Only slight variation was boserved in the number of follicles in recipient ewes. Among donor ewes receiving FSH-P in addition to Synchro-Mate B, 71% were detected in estrus within 48 h of implant removal vs 55% of the recipients.     

Effect of season and duration of FSH treatment on embryo production in sheep

Thirty-six mature Manchega ewes were used in two experiments to determine the effect of season and of 2- or 3-d FSHp treatment on the ovulation rate and number of transferable embryos produced. During the breeding season, estrus was synchronized with FGA (30 mg for 13 d). Begining 48 or 24 h before sponge removal, each ewe received two daily injections of 4-4-3-3-1-1 or 5-5-3-3 mg of FSHp. Concurrently with the two last injections both groups were administered 100 mug of LH. Ewes were tested for estrus and 6 or 7 d later were laparotomized and surgically flushed to recover embryos. The number of corpora lutea (CL), the total number of embryos and of viable embryos were recorded. Six months later (nonbreeding season) the design was repeated, with each ewe receiving the opposite treatment to that received in the fall. Response in ovulation rate and number of viable embryos did not differ between seasons. Mean (SEM) numbers of observed CL and embryos recovered were higher (P<0.001) with the 3-d treatment (8.7+/-5.8 and 7+/-4.8) than with the 2-d treatment (5.8+/-3.2 and 4.4+/-3) when pooled over the two seasons. The mean number of transferable embryos was higher (P<0.01) with the 3-d (4.2+/-3.9) than with the 2-d treatment (2.5+/-2.3).     

Active immunization of post-pubertal heifers against prostaglandin F2α to suppress oestrous behaviour: effect of adjuvant and dose of immunogen

Two experiments were performed to develop an effective prostaglandin F_2α immunization protocol to suppress oestrous behaviour in beef heifers. In Experiment 1, a 3 × 2 factorial plan (n=4–5 per treatment) was used to test three doses (3.3, 10 and 30 mg) of a prostaglandin F_2α- human serum albumin (PGF-HSA) conjugate as the immunogen and two adjuvants, GNE (proprietary product; Intervet, The Netherlands) and diethylaminoethyl (DEAE)-dextran. Heifers (n=5) in a control group were untreated. Booster immunizations were given on Days 42 and 145 after the primary immunization (Day 0) and data collection for statistical purposes ended on Day 297. After Day 42 the incidence of oestrous behaviour was: (1) greater (P < 0.05) for control than immunized heifers (4.3 and 2.2, respectively), (2) greater (P < 0.05) for heifers immunized using GNE than for heifers immunized using DEAE-dextran (2.6 and 1.9, respectively), and (3) greater for heifers immunized with 30 mg of immunogen than for those immunized with either 3.3 or 10 mg (3.1, 1.7 and 1.9, respectively). Suppression of oestrous behaviour was accompanied by formation of a persistent corpus luteum (CL). Persistent CL were formed in ten of the 28 immunized heifers and the mean (± standard error of the mean) duration of persistence was 397 ± 85 days. In Experiment 2, a 2 × 2 factorial plan (n=6–7 per treatment) was used to test two doses (1 and 10 mg) of the PGF-HSA conjugate as the immunogen and two adjuvants, non-ulcerative Freund's adjuvant (NUFA) and DEAE-dextran. A control group was untreated (n=6). Booster immunization was given on Day 183 after the primary immunization (Day 0) and the experiment finished on Day 384. Antibody titres were higher (P < 0.05) in NUFA-treated heifers than in DEAE-dextran-treated (1 mg) heifers in the 183- to 283-day period. After Day 183, oestrous behaviour was suppressed in 26 out of the 27 immunized heifers. Persistent CL were maintained for longer (P < 0.05) in NUFA-treated heifers (245 days) than in DEAE-dextran-treated heifers (166 days) but there was no difference due to dose of immunogen (208 and 203 days, 1 and 10 mg, respectively). It is concluded that immunization against PGF-HSA results in suppression of oestrous behaviour in heifers due to prolongation of the life-span of the CL; however, efficacy of response is dependent on the immunization regime used.     

Effects of exogenous ovine growth hormone on reproduction, serum hormone profiles and milk characteristics in early-postpartum fine-wool ewes nursing single or twin offspring

After parturition (Day 0), 31 mature spring-lambing, fine-wool ewes were randomly allotted to one of six groups. Treatments were lambs suckled (one or two) and ovine growth hormone (oGH; 0, 5 or 10 mg). Growth hormone was administered subcutaneously daily from Days 6 to 25. Milk characteristics were determined on Day 26. Ewes were observed for estrus beginning on Day 27. Serum insulin did not differ (P > 0.10) between suckling intensity before or after oGH treatment on Days 6, 15 or 25. Likewise, no difference (P > 0.10) in serum insulin was detected among ewes receiving 0, 5 or 10 mg oGH. Ewes suckling twins had higher (P < 0.05) serum growth hormone on Day 6 (before beginning oGH treatment) than ewes suckling single lambs. In ewes receiving 0, 5 and 10 mg oGH, serum growth hormone differed (P < 0.01) in a linear fashion 1 h after treatment was initiated on Day 6 and continued through Hour 6. Serum growth hormone on Days 15 and 25 differed among groups both before and after oGH was administered (P < 0.01). Suckling intensity did not affect (P > 0.10) milk or milk protein and fat yields; however, oGH increased (linear, P < 0.05) fat but did not affect milk or protein yields. Interval from parturition to estrus did not differ (P > 0.20) in ewes suckling single or twin offspring. Likewise, no differences (P > 0.20) in interval length were noted in ewes receiving 0, 5 or 10 mg oGH. Suckling intensity and oGH administration for 20 d had little effect on postpartum interval or milk characteristics during the first 30 d after lambing in fine-wool ewes.     

Myometrial activity and plasma progesterone and oxytocin concentrations in cycling and early-pregnant ewes

Myometrial activity and plasma progesterone (P) and oxytocin (OT) were measured in early pregnant (n = 5) and cycling (n = 5) ewes. Electromyography (EMG) leads and jugular and inferior vena cava (IVC) catheters were surgically placed in ewes about 1 wk before data collection. When ewes returned to estrus, they were bred to either an intact or vasectomized ram. Continuous EMG data were collected, and blood samples were collected twice daily from day of estrus (Day 0) until Day 18. Ewes bred with an intact ram were checked surgically for pregnancy on Day 20. Computerized, quantitative analysis of EMG events showed no difference in signal from the right to left uterine horns, and no differences between pregnant and cycling ewes (p less than 0.05) until Days 14-18 when nonpregnant ewes returned to estrus and had increased EMG activity. The mean number of EMG events 180-900 s in length decreased in pregnant ewes, but this difference was not significant (p less than 0.05). Jugular plasma progesterone (P) levels confirmed corpus luteum (CL) formation in all ewes, and no differences in P between pregnant and nonpregnant ewes were measured until Days 14-18, when cycling ewes underwent luteolysis and pregnant ewes maintained CL. IVC plasma oxytocin concentrations were increased in pregnant ewes compared to concentrations in nonpregnant ewes on Days 5-13 (p less than 0.05), and the difference was largest at Day 6 (means +/- SEM pg/ml: pregnant = 68.7 +/- 13.9, nonpregnant = 30.9 +/- 19.9).(ABSTRACT TRUNCATED AT 250 WORDS)     

Melatonin advances june breeding and fall lambing in range and farm-flock type ewes

Influence of melatonin on reproductive performance was evaluated by randomly allotting Polypay-type ewes to four treatments: controls in drylot, melatonin-treated ewes in drylot, controls on range, and melatonin-treated ewes on range. An additional group of Targhees and Rambouillets was randomized by breed as control ewes or melatonin-treated ewes to test effect of melatonin in range ewes. All ewes were supplemented with 0.34 kg/head alfalfa-barley (1:1) pellets from 1600 to 1630 h daily, from April 15 to June 30. Ewes maintained on range received no further supplementation, while ewes in drylot received alfalfa pellets for maintenance. Melatonin was fed at 10 mg hd(-1) d(-1) in the pellet to designated ewes in drylot or on range. Three rams were put with each group of ewes on June 1 and rotated among groups at 7-d intervals during the first 30 d of breeding to reduce sire differences. After the first 30 d, ewe groups were combined with all rams. Melatonin induced (P < 0.01) an earlier onset of estrus (approximately 17 d) as indicated by earlier lambing dates in Polypay-type, Rambouillet, and Targhee ewes managed on spring range. Melatonin also increased (P < 0.01) the number of ewes that conceived during the first 30 d of breeding (June) for both management treatments (drylot and range) and for all breeds.     

A single intrauterine infusion of sustained recombinant ovine interferon-tau extends corpus luteum lifespan in cyclic ewes

Delivery carriers were developed to permit sustained release of recombinant ovine tau-interferon (roIFN-tau) to increase corpus luteum (CL) lifespan in cyclic ewes following a single intrauterine administration on Day 10 post estrus. A single infusion with 1.7 mg roIFN-tau covalently bound to carboxymethyl biogel agarose (carbodiimide coupling) significantly increased the interestrus interval (P < 0.01) in treated (n = 4) versus control animals (n = 6), whereas liposomally encapsulated roIFN-tau administered to experimental ewes (n = 8) versus control ewes (n = 6) was less effective (P < 0.05). RoIFN-tau covalently bound to trisacryl (glutaraldehyde coupling) was also effective in cyclic ewes (n = 6), but covalent binding to Eupergit C through oxirane bonds yielded ineffective preparations. Ewes that were given 1.7 mg soluble roIFN-tau (n = 8) displayed slight extension of the CL lifespan compared with ewes that were given 1.7 mg soluble BSA (n = 6), but this extension lacked significance in the Mann-Whitney U-test (P > 0.05). These results are consistent with previous data from experiments performed with daily intrauterine infusion of soluble, native or recombinant oIFN-tau. In addition, because CL maintenance requires only a single administration, these methods are efficient and simple to use since they avoid animal catheterization and allow for reduced injection frequency. Moreover, they may permit the use of smaller amounts of IFN. It is concluded that the use of oIFN-tau sustained in some delivery systems may allow for the development of an experimental sheep pseudopregnancy model.     

Breeding ewes out-of-season using melengestrol acetate, one injection of progesterone, or a controlled internal drug releasing device

A series of studies was designed to identify methods of improving out-of-season breeding success in ewes. In Experiment 1, 190 mature ewes were assigned to receive in April, either: (A) a control ration of 0.3 kg corn twice daily for 8 d before ram introduction (control ewes n=49), (B) the control ration containing 0.125 mg of melengestrol acetate (MGA) in 0.3 kg corn (MGA8a ewes n=46), (C) the control ration or 7.5 d followed by 1 feeding of 0.5 mg MGA in 0.3 kg corn (MGA1 ewes n=48), or (D) the control ration plus a 20 mg i.m. injection of progesterone on D 8 (P ewes n=47). Ewes were exposed to rams for 21 d. A greater percentage of MGA8a and P ewes lambed than did control ewes (P < 0.04). The lambing rate was greatest among MGA8a (P < 0.02 vs. control), intermediate among P ewes (P < 0.19 vs. control) and least among MGA1 and control ewes (P > 0.79). In Experiment 2, 70 mature ewes were assigned to receive in June, either: (A) a control ration of 0.3 kg of corn twice daily for 8 d before to ram introduction (control ewes n=25), (B) the control ration containing 0.125 mg of MGA per 0.3 kg corn (MGA8b ewes n=21), or (C) the control ration and simultaneous treatment of ewes with a progesterone-containing controlled internal-drug releasing device (CIDR ewes n=24). Ewes were exposed to rams for 21 d. Both CIDR and MGA8b ewes exhibited estrus earlier than did control ewes (P < 0.01). The CIDR ewes exhibited estrus earlier than did the MGA8b ewes (P < 0.05). A greater percentage of ewes treated with CIDR or MGA8b lambed than did control ewes (P < 0.01), with more CIDR ewes lambing than MGA8b ewes (P < 0.01). The lambing rate was greater in CIDR ewes than in control ewes (P < 0.04). These data provide evidence that several options exist to improve pregnancy success in ewes bred out of season and that success varies with method of treatment.     

A new approach to enhance reproductive performance in sheep using royal jelly in comparison with equine chorionic gonadotropin

The objective was to compare the effects of royal jelly (RJ) and eCG treatments on reproductive performance of ewes synchronized using intravaginal progesterone-releasing devices. Forty-two cycling Awassi ewes were treated intramuscularly (i.m.) with 15 mg PGF2alpha. On the following day, all ewes were administered with CIDR-G for 12 days and were randomly allocated to three (RJ, eCG and control) groups of 14 ewes each. Ewes in the RJ-treated group received daily i.m. treatments of 400mg RJ during the period of CIDR-treatment. Each ewe in the eCG-treated group received an i.m. treatment of 500 IU eCG at the time of CIDR-G removal (day 0) and no further treatment was given to ewes in the control group. Ewes were exposed to four fertile rams for 72 h, from the time of CIDR-G removal, and checked for breeding marks at 6-h intervals. Blood samples were collected from day -13 until day 0 and thereafter until day 19 for progesterone analysis. Royal jelly treatment resulted in a greater rate of decline and lower (P<0.02) progesterone concentrations between days -10 and 0 than eCG-treated and control ewes. Expression of estrus was similar among the three groups and intervals to onset of estrus were shorter (P<0.01) in RJ-treated (31.3h) and eCG-treated (29.8h) than control (41.3h) ewes. First-cycle pregnancy and lambing rates were greater (P<0.05) in RJ-treated (71.4 and 71.4%) and eCG-treated (85.7 and 78.6%) than in control (42.9 and 35.7%) ewes, respectively. Results demonstrate that the treatments of RJ and eCG in conjunction with CIDR-G were similarly effective in induction of estrus and improvement of pregnancy and lambing rates.     

Effect of ovine conceptus secretory proteins and purified ovine trophoblast protein-1 on interoestrous interval and plasma concentrations of prostaglandins F-2 alpha and E and of 13,14-dihydro-15-keto prostaglandin F-2 alpha in cyclic ewes

Conceptus secretory proteins (oCSP) were obtained from medium in which sheep conceptuses, collected on Day 16 of pregnancy, were cultured for 30 h. A portion of the culture medium (500 ml) was prepared for intrauterine infusion by concentrating the proteins by Amicon ultrafiltration (Mr 500 cutoff). A second portion (500 ml medium) was used to purify sheep trophoblast protein one (oTP-1). Proteins remaining after oTP-1 purification were concentrated and then passed through an anti-oTP-1 sepharose CL-4B affinity column to remove any remaining oTP-1 (oCSP-oTP-1). Serum proteins (oSP) were collected from a Day-16 pregnant ewe and diluted for infusion. Catheters were placed in the uterus of cyclic (Day 10) ewes. The following combinations of proteins were infused: 0.75 mg oCSP + 0.75 mg oSP (5 ewes), 0.75 mg oCSP - oTP-1 + 0.75 mg oSP (4 ewes), 0.05 mg oTP-1 + 1.45 mg oSP (5 ewes) and 1.5 mg oSP only (5 ewes). Infusions were twice daily on Days 12 and 13 (08:00 and 17:00 h) and once on Day 14 (08:00 h). On Day 14, ewes were injected intravenously at 08:00 h with 0.5 mg oestradiol-17 beta. Blood sampling began 30 min before oestradiol injection and continued every 30 min for 10 h. On Day 15 ewes received 10 i.u. oxytocin intravenously (08:00 h). Blood samples were collected 10 min before oxytocin and every 10 min for 1 h after oxytocin injection. Concentrations of prostaglandin (PG) F, PGE-2/PGE-1 (PGE) and 13,14-dihydro-15-keto-PGF-2 alpha (PGFM) were measured by specific radioimmunoassay. Ewes treated with oTP-1 and oCSP had longer (P less than 0.05) interoestrous intervals (27 and 25 days, respectively) compared to ewes treated with oSP and oCSP--oTP-1 (19 and 19 days, respectively) (s.e.m. = 1.56 days). These results indicate that oTP-1 alone is as potent as total conceptus secretory proteins in extending luteal maintenance. Ewes treated with oTP-1 and oCSP had no increase in PGF after oestradiol injection while production of PGF did increase 6-10 h after oestradiol in ewes treated with oSP and oCSP--oTP-1. PGFM was correlated with PGF concentrations (r = 0.57, P less than 0.01) although presence or absence of increases in production of PGFM for the treatment groups were not the same as those for PGF. No effects of treatment on PGE were detected.(ABSTRACT TRUNCATED AT 400 WORDS)     

Short-term treatment with a controlled internal drug releasing (CIDR) device and FSH to induce fertile estrus and increase prolificacy in anestrous ewes

The objectives were to evaluate, in anestrous ewes, the effectiveness of a CIDR-G device (0.3 g progesterone) administered for 5 d to induce estrus; and FSH (Folltropin; 55 mg NIH-FSH-P1 equivalent) in saline:propylene glycol (1:4) 24 h before insert removal (Day 0), to increase ovulation rate and prolificacy. Ewes of mixed breeding were assigned at random to 3 treatments: control (C; n = 125), 5 d progesterone (P5; n = 257) and 5 d progesterone plus FSH (P5F; n = 271). Intact rams were joined at insert removal and ewes were observed every 24 h for 3 d. On Day 14, the ovulation rates of all ewes detected in estrus in the treated groups were determined using transrectal ultrasonography. Rams were removed on Day 26 to 31. Ewes were examined for pregnancy then, and again 20 to 25 d later to detect ewes that conceived to the second service period. Percentage of ewes marked by rams was higher in progesterone-treated (77%) than in C (20%; P < 0.01), but did not differ between P5 and P5F. The ovulation rate (1.95+/-0.04) did not differ due to FSH. Conception (68%) and pregnancy (52%) rates were higher in progesterone-treated (P < 0.01) than in C (0%) ewes. Estrous response varied quadratically with time after ram introduction, and the conception rate varied quadratically with the time of observation of onset of estrus. Over two service periods more progesterone-treated than C ewes lambed (65 vs 45%; P < 0.01). Lambs born per ewe exposed (0.7+/-0.1, 1.0+/-0.1, and 1.1+/-0.1 for C, P5 and P5F, respectively) was increased by progesterone (P < 0.05). Litter size to the first service period (1.59+/-0.04) and overall (1.54+/-0.03) did not differ among treatment groups. FSH-treated ewes tended to have more lambs (1.67+/-0.1) than did ewes receiving progesterone alone (1.5+/-0.1; P = 0.06) and than did ewes lambing to the second service period (1.5+/-0.1; P = 0.06). In summary, a 5-d progesterone pre-treatment of anestrous ewes induced estrous cycles and increased the pregnancy rates. A single injection of FSH only tended to increase litter size.     

Effects of prostaglandin F(2alpha) dosage of synchronizing ovine estrus using a modified single injection regimen

Two dosages of prostaglandin F(2alpha) (PGF) were tested to evaluate their efficacy to synchronize estrus in ewes. A selectively administered single injection regimen was used. A total of 329 Targhee, Suffolk x Targhee and Finn x Targhee ewes 3 to 6 yr of age were allotted within breed type to one of three treatment groups: control, 10 mg PGF or 15 mg PGF. Trials were conducted over a 2-yr period and were replicated twice within each year. In each trial, epididymectomized rams were placed together with the ewes (1 ram:40 ewes) for 2 wk prior to a 35-d breeding exposure. Fertile, semen-tested rams were introduced (1 ram:10 ewes) on Day 1 of the breeding period. All ewes that had not mated by Day 5 received one of the three randomly assigned treatments. Treatment with PGF-10 or PGF-15 increased the percentage of ewes mating (and the percentage of those conceiving) 32 to 56 h following treatment compared with the control ewes (P<0.01). Within 56 h following treatment, 11.7, 56.2 and 65.5% of the control and the PGF-10 and PGF-15 treated groups, respectively, had mated. The percentage of ewes that conceived within 56 h was 10.7, 42.3 and 47.8, respectively. Treatment did not affect fertility, prolificacy or fecundity (P>0.05), irrespective of breed. A treatment by breed interaction was found: Finn x Targhee ewes treated with PGF-15 had a lower (P<0.01) lambing rate than those treated with PGF-10 or those in the control group. Lamb birth weight and lamb mortality were not affected by treatment (P>0.05). The cumulative lambing percentage was higher (P<0.01) at 157 d following the introduction of rams for ewes treated with PGF than for the controls. These results indicate that at a dose of 10 or 15 mg i.m. PGF was effective in synchronizing estrus in ewes within 56 h post treatment.     

Comparison of a controlled internal drug release device containing progesterone with intravaginal medroxyprogesterone sponges for estrus synchronization in ewes

Intravaginal progestagens have been used for many years to synchronize estrus in ewes. This experiment compares two such treatments: 60 mg medroxyprogesterone (MAP) sponges and a controlled internal drug release (CIDR) device containing 366 mg natural progesterone. No pregnant mare serum gonadotropin (PMSG) was used. Treatments were given to groups of 10 to 20 ewes for 14 d at various times during breeding season. Rams were introduced 1 d after treatment removal, and day of mating was recorded. Rams were removed after 3 d. Pregnancy was checked with ultrasound 60 d later. There was no diffeence in rate of marking by rams (88%) or pregnancy rate (57%) between treatments. Ewes receiving CIDR devices showed estrus earlier and with closer synchrony (P < 0.01). The CIDR device is comparable to the MAP sponge for estrus synchrony during the breeding season, and reasonable fertility can be achieved without the use of PMSG.     

Response of anestrous ewes to norgestomet and PMSG

A 10-day treatment regime with a subcutaneous ear implant containing 3 mg of norgestomet, accompanied by an intramuscular injection of 1.5 mg norgestomet and 0.5 mg estradiol valerate (EV) on day 1 and 750 I. U. pregnant mares serum gonadotropin (PMSG) given intravenously on day 10, proved effective in eliciting estrus in 72% of 110 anestrous ewes within 5 days of treatment. Ewes which were treated in months closer in proximity to the normal breeding scason responded with significatly increased induction of estrus, with 71, 37, 59, 74, and 97% in estrus for ewes which were treated in February through June, respectively. Comparable estrous response in nontreated, control ewes was 0, 13, 0, 10, and 24% during February through June, respectively. (Treated vs controls, P<.01). Pregnancy rate to first service of ewes in estruc was 51% in treated and 30% in control ewes (P>.10). Overall pregnancy rate for all ewes in both groups was 36% in treated and 3% in control ewes during 5 or 16 days of breeding, respectively (P<.01).     

Human menopausal gonadotropin induces ovulation in sheep, but embryo recovery after prostaglandin F2alpha synchronization is compromised by premature luteal regression

Using pregnant mares' serum gonadotropin (PMSG) and follicle stimulating hormone (FSH-P) as conventional gonadotropins, human menopausal gonadotropin (hMG) was tested for its comparative ability to induce multiple ovulations in sheep. Estrous cycles were synchronized using either prostaglandin F(2alpha) (PGF(2alpha)) or progestogen (MAP)-impregnated pessaries. During the mid-luteal phase, control ewes received serial saline injections, whereas test females (which also served as embryo donors) received either a single PMSG injection (1200 IU) or serial injections of FSH-P (total, 21 mg) or hMG (total, 1350 IU) over 3.5 d. These sheep were naturally mated and artificially inseminated (AI) in utero . Number of CL and transferable-quality embryos 5 d after AI was greater (P<0.05) in FSH-P-and hMG-treated donors than in PMSG-treated ewes. The lower number of transferable-quality embryos produced by PMSG-treated donors was attributed to a reduced (P<0.05) fertilization rate compared with that of the other treatment groups. There were no differences (P>0.05) in daily circulating estradiol-17beta and progesterone concentrations among the gonadotropin treatment groups. Gonadotropin-treated ewes demonstrated estrus approximately 24 h earlier than control ewes and, therefore, exhibited an accelerated estradiol-17beta surge and rise in circulating progesterone. Progesterone production in gonadotropin-treated ewes was also more variable than in the controls; this was due, in part, to premature luteal regression which occurred in 4 of 10 PMSG-, 3 of 10 FSH-P- and 6 of 10 hMG-treated ewes also given PGF(2alpha). Ewes with prematurely regressing CL experienced transient luteal tissue development within 4 d of ovulation and produced no embryos. Overall results 1) demonstrate that serial administration of hMG induces multiple ovulations in sheep comparable to FSH-P, and 2) suggest that PGF(2alpha) treatment during ovulation induction adversely affects newly formed luteal tissue compromising subsequent embryo recovery.     

Induction of estrus and superovulation in seasonally anestrous ewes

The induction of estrus in 17 previously cycling nulliparous ewes, 9 to 10 months of age, was attempted with Medroxyprogesterone acetate (MAP) pessaries during the early anestrous period (March-April). Ewes were verified to be anestrous by the lack of estrous behavior in the presence of a vasectomized ram and by a radioimmunoassay for serum progesterone in two samples taken 7 days apart showing less than 1 ng/ml serum progesterone. Superovulation was attempted with injections of either FSH or FSH + LH. MAP vaginal pessaries remained in place for a period of 12 days and FSH was administered to all ewes (IM) at 12 hr intervals over a 3 day period; 5 mg was injected twice on day 11 after pessary insertion, followed by 4 and 3 mg injections twice daily on each succeeding day, for a total of 24 mg per ewe. Nine ewes were given 25 mg LH (IV) within 8 hrs after the onset of behavioral estrus in addition to FSH. Ewes were hand-mated to several rams at 12 hr intervals throughout the estrus period. Ovulation and fertilization rates were recorded for each ewe following midline laparotomy and embryo collection. All ewes were in estrus between 36 and 48 hrs after removal of the MAP pessaries. In ewes injected with FSH only, 8 of 8 ovulated with a mean ovulation rate of 6.0 +/- 4.4 and a fertilization rate of 70%. Nine of 9 ewes receiving both FSH + LH ovulated with a mean ovulation rate of 13.9 +/- 13.1 and a fertilization rate of 72%. Statistical analysis by Students t-test resulted in differences in number of ova recovered (P<.05) between FSH only and FSH + LH treated ewes and a trend towards increased ovulation rate in FSH + LH treated ewes. These results show that early seasonally anestrous ewes can be successfully induced and synchronized for estrus with MAP pessaries and the number of ova recovered is increased with the inclusion of LH in the superovulation regime.     

Sex behavior and hormone responses in ewes administered testosterone propionate

Two ewes were administered testosterone propionate and subsequent plasma testosterone concentrations determined and male sex behavior recorded. Initially ewes were administered 50 mg of testosterone propionate every other day for 20 days. Within 6 days following the first injection, concentrations of testosterone in plasma increased to 8.0 to 10.0 ng/ml. A 50 mg injection of testosterone propionate administered every 10 days thereafter maintained concentrations of plasma testosterone at 1.0 to 3.0 ng/ml. Sex behavior tests conducted with non-estrus and estrus ewes showed that both testosterone treated ewes developed male sex behavior similar to a ram. Ewes in estrus were mounted by testosterone treated ewes an average of 6.7 ± 1.2 times during a 10 minute test whereas none of the non-estrus ewes were ever mounted. Silastic implants containing testosterone propionate placed in the ewes 83 days following the first injection maintained concentrations of plasma testosterone at 6.0 to 8.0 ng/ml for a 20 day period. Therefore, administration of testosterone propionate to ewes effectively stimulates male sex behavior and would obviate the necessity for vasectomized rams for estrus detection.     

Cervical dilation, conception rate, and concentrations of progesterone and estradiol-17B in postpartum ewes treated with porcine relaxin

Experiments were conducted to determine the effects of porcine relaxin (pRLX) on cervical dilation and conception rates in postpartum ewes. In Experiment 1, ewes received medroxyprogesterone acetate (MAP) sponge on day 16 (day 0 = lambing) and 750 IU pregnant mare serum gonadotropin (PMSG) at sponge removal on day 30. Control ewes received saline and relaxin-treated (RLX) ewes received 0.5 mg pRLX (>/= 3000 U/mg) i.m. at 24 h and 1.0 mg pRLX at 36 h after PMSG. All ewes were inseminated (Al) at 55 h after PMSG with 0.4 ml fresh semen. The proportion of RLX treated ewes (6 6 ) in which the cervix was penetrated was greater (P < 0.05) than in Control ewes (0 5 ). However, ova recovery rate was lower (P < 0.05) for RLX ewes (1 6 ) than for control ewes (5 5 ). In Experiment 2, ewes between Days 90 to 120 post partum received MAP sponges for a period of 8 d and 750 IU PMSG at sponge removal. Control ewes (n = 9) received saline; RLX-1 ewes (n = 8) received 0.5 mg pRLX at 24 h and an additional 0.5 mg pRLX at 36 h after PMSG; and RLX-1.5 ewes (n = 9) received 0.5 mg pRLX at 24 h and an additional 1.0 mg pRLX at 36 h after PMSG. Ewes were mated to rams at estrus, and cervical dilation was checked at 55 h after PMSG. The cervix could not be penetrated in any of the ewes. Conception rates on Day 26 were 66, 56 and 63% for control, RLX-1 and RLX-1.5 groups, respectively. These results demonstrate that the effect of relaxin on cervical dilation and conception rate is dependent upon the postpartum stage of the ewes.     

Ovarian morphology and the concentration of steroids, and of gonadotrophins during the breeding season in ewes actively immunized against oestradiol-17 beta or oestrone

Ewes were actively immunized against oestrone-6-(O-carboxymethyl)-oxime-bovine serum albumin, 17 beta-oestradiol-6-(O-carboxymethyl)oxime-bovine serum albumin or bovine serum albumin (controls). All 4 control ewes, 1 of 5 oestradiol-immunized ewes and 1 of 5 oestrone-immunized ewes had regular oestrous cycles. The other animals displayed oestrus irregularly or remained anoestrous. The plasma concentrations of LH and, to a lesser degree, FSH were increased relative to those in control ewes on Days 11-12 after oestrus or a similar total period after progestagen treatment in ewes not showing oestrus. The ovaries were examined and jugular venous blood, ovarian venous blood and follicular fluid were collected at laparotomy on Days 9-10 of the oestrous cycle. The ovaries of immunized ewes were heavier than those of control ewes. There were no CL in 5 of the immunized ewes but in the other 5 there were more CL than in the control ewes. Ovaries from 4 of 5 oestrone-immunized ewes contained luteinized follicles, while ovaries from 4 of 5 oestradiol-immunized ewes contained very large follicles with a degenerated granulosa and a hyperplastic theca interna. Both types of follicles produced progesterone, detectable in ovarian venous plasma and production of other steroids, particularly androstenedione, was also increased. The steroid-binding capacity of plasma was increased in the immunized ewes. The binding capacity of follicular fluid for oestradiol-17 beta and oestrone was similar to that of jugular venous plasma from the same ewes. These results suggest that immunization against oestrogens disrupts reproductive function by interfering with the feedback mechanisms controlling gonadotrophin secretion.     

Relationship of oestrus synchronization method, circulating hormones, luteinizing hormone and prostaglandin F-2 alpha receptors and luteal progesterone concentration to premature luteal regression in superovulated sheep

Ewes were treated with exogenous follicle-stimulating hormone (FSH) and oestrus was synchronized using either a dual prostaglandin F-2 alpha (PGF-2 alpha) injection regimen or pessaries impregnated with medroxy progesterone acetate (MAP). Natural cycling ewes served as controls. After oestrus or AI (Day 0), corpora lutea (CL) were enucleated surgically from the left and right ovaries on Days 3 and 6, respectively. The incidence of premature luteolysis was related (P less than 0.05) to PGF-2 alpha treatment and occurred in 7 of 8 ewes compared with 0 of 4 controls and 1 of 8 MAP-exposed females. Sheep with regressing CL had lower circulating and intraluteal progesterone concentrations and fewer total and small dissociated luteal cells on Day 3 than gonadotrophin-treated counterparts with normal CL. Progesterone concentration in the serum and luteal tissue was higher (P less than 0.05) in gonadotrophin-treated ewes with normal CL than in the controls; but luteinizing hormone (LH) receptors/cell were not different on Days 3 and 6. There were no apparent differences in the temporal patterns of circulating oestradiol-17 beta, FSH and LH. High progesterone in gonadotrophin-treated ewes with normal CL coincided with an increase in total luteal mass and numbers of cells, which were primarily reflected in more small luteal cells than in control ewes. Gonadotrophin-treated ewes with regressing CL on Day 3 tended (P less than 0.10) to have fewer small luteal cells and fewer (P less than 0.05) low-affinity PGF-2 alpha binding sites than sheep with normal CL. By Day 6, luteal integrity and cell viability was absent in ewes with prematurely regressed CL. These data demonstrate that (i) the incidence of premature luteal regression is highly correlated with the use of PGF-2 alpha; (ii) this abnormal luteal tissue is functionally competent for 2-3 days after ovulation, but deteriorates rapidly thereafter and (iii) luteal-dysfunctioning ewes experience a reduction in numbers of small luteal cells without a significant change in luteal mass by Day 3 and, overall, have fewer low-affinity PGF-2 alpha binding sites.