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.     

Accelerated lambing using exogenous progesterone and the ram effect.

An experiment was conducted to determine whether controlled internal drug release devices-type G (CIDR-G) could be used in conjunction with the ram effect to advance the breeding season and lambing and thereafter could be reapplied to stimulate breeding of ewes to produce a second lambing in late summer. Finn crossbred and Columbia ewes were treated with CIDR-G from July 6 to 18. Rams, which had been isolated from ewes, were joined with the flock upon CIDR-G removal. All 59 CIDR-G-treated ewes exhibited estrus, and 55 lambed from breeding within a 30-d period after CIDR-G withdrawal. Eighteen of 19 contemporary control ewes (no CIDR-G) were bred, and 16 lambed. Ewes that had lambed from the CIDR-G and control groups were retreated as before, with CIDR_G inserted March 1 and withdrawn March 13, concomitant with sudden exposure to rams. Of 55 CIDR-G-treated sheep, 53 were bred and 45 lambed. All 16 control ewes were bred and lambed. A second experiment was conducted to determine whether treatment with CIDR-G and the ram effect was effective in mid-spring. The CIDR-G were applied for 12 d and removed on May 1 or 6 from Finn crossbred, Columbia, and Polypay ewes. Rams were introduced upon CIDR-G withdrawal. Of 59 CIDR-G-treated ewes, 58 exhibited estrus and 45 lambed. Twenty-three of 30 contemporary control ewes were bred, and 20 lambed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of cohabitation with white-faced ewes on estrous activity of Hampshire and Suffolk ewes exposed to rams in June

Two groups of 24 Hampshire and 26 Suffolk purebred ewes each were used to study effects of cohabitation with cyclic white-faced (WF) ewes on estrous activity in June. Ewes lambed in January, February and March and had been isolated from mature rams since the previous fall breeding. From June 1 to July 2, treated (T) ewes were exposed to vasectomized rams and to 65 WF ewes; control (C) ewes were exposed only to vasectomized rams. Ovulation was assessed with biweekly serum progesterone assays; crayon marks were used to detect estrus. Daily observations of ram behavior were conducted to assess sexual activity of rams joined with T and C ewes. Cohabitation with WF ewes increased (P less than .01) ovulation percentages from 46% in C (42% for Hampshires and 50% for Suffolks) to 76% in T ewes (79% for Hampshires and 73% for Suffolks). Mating percentage also was increased (P less than .05) by cohabitation with WF ewes from 14% for C ewes to 30% for T ewes. Rams with T + WF ewes spent more (P less than .05) time checking ewes for estrus than did rams with C ewes. Hence, cohabitation with cycling WF ewes increased ovulation and mating percentages. Many acyclic T ewes first ovulated after 10 or more days of teasing, possibly due to increased ram contact in the presence of WF ewes.     

Effects of ram preexposure and ram breed on fertility of ewes in summer breeding

Suffolk x Rambouillet ewes were used in two consecutive years to test the ability of Dorset and Suffolk yearling rams to stimulate ovulation and estrus in early summer (late June and July) breeding. After spring weaning about June 1, ewes were randomly divided into three groups and for 2 wk either were isolated from rams or were preexposed to either yearling Dorset or Suffolk rams by penning of rams in proximity to ewes. Ewes then were rerandomized into two groups for joining with either yearling Dorset or Suffolk rams fitted with marking harnesses. Serum progesterone profiles and crayon marks were used as indicators of ovulation and estrus. Overall lambing rate was not different among preexposure treatments for the 2 yr. However, early lambing rate (in the first 14 d of lambing season) was significantly affected by preexposure group (24% for Dorset vs 9% for Suffolk and 10% for isolation), especially in the 2nd yr (31% for Dorset vs 8% for both Suffolk and isolation). Ewes preexposed to Dorsets also lambed 10 d earlier (P less than .05) than ewes preexposed to Suffolks in yr 2, but the groups did not differ in yr 1. Ewes exposed to Dorset rams for breeding had higher overall lambing rates than ewes bred to Suffolks (75% vs 54%), especially in the 1st yr (77% vs 48%). Lambs sired by Dorset rams were born 6 d earlier in yr 1 (P less than .05) but only 1 d earlier in yr 2. Data from both years indicate that Dorsets are superior to Suffolks in ability to sire lambs in fall lambing systems.     

Reproductive performance of Suffolk and Suffolk-cross ewes and ewe lambs exposed to vasectomized rams before breeding

Multiparous Suffolk and Suffolk-cross ewes were randomly allotted to treatments within breed and year to measure effects of ram exposure, during transition from anestrus to breeding activity, on reproductive performance. Treatments were: 1) ewes joined with two mature vasectomized Rambouillet rams for 15 d before breeding (DC), 2) ewes maintained across a net wire fence from two vasectomized rams for 15 d before breeding (FC) and 3) ewes maintained approximately 400 m away from rams (NC). At the end of the 15 d, all ewes were placed in one pasture and mated to three fertile Suffolk rams during a 34-d breeding season. A total of 96 Suffolk and 177 Suffolk-cross ewes was utilized during the 3-yr experiment. A greater (P less than .05) prebreeding ovulation percentage was observed in DC and FC than in NC ewes. Mating and lambing occurred approximately 6 d earlier for DC or FC ewes than for NC ewes. A similarly designed experiment was conducted using Suffolk and Suffolk-cross ewe lambs allotted to treatments within breed and year to measure effects of ram exposure during the natural breeding season, but prior to breeding. Treatment differences were not detected (P greater than .05) for date of first observed estrus, date of lambing, percentage of ewes lambing in the first 17 d of the lambing season, number of lambs born per ewe lamb exposed or number of lambs born per ewe lamb giving birth.     

Effects of melatonin and progesterone administered to ewes in spring and summer

Melatonin (MEL) was evaluated for effects on LH, prolactin (PRL) and fertility in spring (Exp. 1, 2) and summer (Exp. 3 to 5). In Exp. 1, 17 ovariectomized ewes bearing estradiol implants were fed 3 mg MEL or vehicle for 44 d beginning May 1. Melatonin decreased (P less than .001) PRL levels but had no effect on LH secretion and response to GnRH. In Exp. 2, 12 ewes each received a 40-d MEL ear implant or a sham implant on March 31. Progesterone-releasing pessaries (CIDR) were applied for 12 d and were withdrawn concomitant with ram joining on May 7. Neither treatment stimulated follicular development or induced estrus or ovulation. Exp. 3 and 4 were contemporary 2 x 2 factorial trials with 24 ewes at each of two locations. Melatonin implants were administered on June 29 and CIDR on July 22. The CIDR were removed and rams (Exp. 3, vasectomized; Exp. 4, fertile) were joined on August 3. Days from introduction of rams to estrus were reduced (P less than .05) by CIDR but not by MEL. All ewes lambed in Exp. 4, and days to estrus and conception were reduced (P less than .001) by CIDR but not by MEL. Exp. 5 was designed like Exp. 4 except that MEL implants were inserted June 20 and rams were joined August 8. Intervals from introduction of rams to estrus were reduced (P less than .01) by both MEL and CIDR treatments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of feed treatment and exogenous estrogen and progestogen on puberty and lambing rates in ewe lambs

Four hundred seventy-four ewe lambs (5 to 6 mo of age) were assigned within breed to two postweaning feed treatments; 1 = alfalfa pellets ad libitum and 2 = alfalfa pellets plus 20% barley or wheat ad libitum. Ten days prior to the start of breeding, approximately one-half of the ewe lambs within each feed treatment were treated with a single injection of 2.5 mg of estradiol valerate and 1.5 mg of norgestomet and implanted with 3 mg of norgestomet for 8 d. At the start of breeding, fertile Suffolk rams were fitted with marking harnesses and penned with ewe lambs; evidence of estrus and breeding was determined on a weekly basis by visual examination for breeding marks. In the second year of the study, 7 to 13 d after recording estrous activity, all marked ewe lambs were bled; and blood was assayed for progesterone. In 1983, 60% of the ewe lambs showed estrus and 11% lambed compared with 48% exhibiting estrus and 30% lambing in 1984 (P less than .01). More (P less than .01) ewe lambs on feed treatment 1 displayed estrus, but more (P less than .05) lambed in the feed treatment 2 group. Steroid treatment resulted in more (P less than .01) ewe lambs showing estrus but fewer lambing (P less than .01). Examination of progesterone concentrations for evidence of ovulation and corpus luteum development indicated that treatment with steroids caused a large percentage of ewe lambs to exhibit estrus. However, many of these failed to develop a corpus luteum and become pregnant.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reproductive responses, progesterone profiles and ovarian characteristics of cycling, fine-wool ewes treated with an inhibitor of progesterone synthesis (epostane)

In Exp. 1, 45 fine-wool ewes received (sc) either 0, 50 or 100 mg epostane (3-beta-hydroxysteroid dehydrogenase inhibitor) to examine effects on return to estrus and conception rates. Treatments were imposed on d 10 of an estrous cycle (estrus = d 0) and jugular blood samples were collected once daily on d 8 and 9, twice daily on d 10 through 13 and once daily from d 14 until first post-treatment estrus or d 20 (15 ewes/treatment). Intensive samples were obtained hourly for 6 h after treatment (d 10; five ewes/treatment). Serum progesterone (P4) before treatment was similar among groups; but by 2 h after treatment, epostane-treated ewes had lower (P less than .10) values than controls. By 6 h post-treatment, serum P4 in ewes receiving 50 (1.0 ng/ml) and 100 (.9 ng/ml) mg epostane was well below control values (3.2 ng/ml). By 7 d after treatment, 93.3% of ewes treated with 50 mg epostane had recycled compared with 66.7 and 33.3% of those receiving 100 and 0 mg, respectively (P less than .10). Similarly, 93.3, 53.3 and 26.7% of ewes receiving 50, 100 or 0 mg epostane, respectively, lambed to breeding within 7 d of treatment (P less than .05). Overall conception rates during a 34-d breeding season were similar among groups. Preweaning performance of offspring did not differ among maternal treatments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased ovulation rate of adult ewes treated with anti-bovine LH antiserum during the normal breeding season

Adult Suffolk ewes (n = 14) were treated on d 10 of the estrous cycle with anti-bovine luteinizing hormone (LH) antiserum. Control ewes (n = 10) were treated with normal horse serum. Estrous behavior and the number of corpora lutea and ovarian follicles were examined at the subsequent estrous cycle. Daily plasma concentrations of progesterone (P4), follicle stimulating hormone (FSH) and estradiol were determined before and after treatment. Ewes treated with antiserum had a higher (P less than .05) ovulation rate (2.7 +/- .2) than did controls (2.1 +/- .1). No differences were found in the numbers of large (greater than 5 mm) or small (less than 5 mm) follicles between treatment groups. Estrus was delayed (P less than .025) approximately .6 d/in ewes treated with antisera. Immunoreactive FSH increased (P less than .05) within 1 d after treatment and remained higher than the controls for 5 d. Peak estradiol concentrations occurred on d 17 for treated ewes compared with peak concentrations on d 15 or 16 for control ewes. The P4 concentrations were generally less (P less than .025) in treated ewes throughout the luteal phase of the treatment cycle. These data demonstrate that ovulation rate is increased in ewes treated with LH antiserum. The marked increase in plasma FSH suggests a possible mechanism whereby ovulation rate is enhanced.     

Influence of breed, number of suckling lambs, and stage of lactation on ewe milk production and lamb growth under range conditions

Milk production and lamb growth were characterized in 118 multiparous, 3- to 7-yr-old Rambouillet, Columbia, Polypay, and Suffolk ewes under spring sage range and high mountain meadow grazing from 28 to 98 d postpartum. Daily milk yield as measured by the lamb suckling weight differential technique did not differ (P greater than .05) among breeds, although milk production of Suffolk ewes tended to be higher than that of the other three breeds. Within the Rambouillet, Columbia, and Polypay breeds, total estimated yield of ewes with twins was 13 to 17% higher than that of ewes with singles, whereas in the Suffolk breed, suckling twins increased total milk yield 61% over that of ewes with singles. Twin lambs induced a larger differential in dam milk production in late lactation (70 to 98 d) than in earlier lactation (28 to 70 d). Number of lambs did not influence milk protein, Ca, or P content (P greater than .05). Fat levels in colostrum and 4-d milk were elevated 14 and 20%, respectively, in ewes suckling twins compared with ewes suckling singles. Under range conditions, Suffolk ewes suckling single or twin lambs lost more BW (12 and 21% of 4-d postpartum body weight, respectively) than Rambouillet (4 and 7%), Columbia (5 and 8%), or Polypay (8 and 8%) ewes. Correlation coefficients of milk production and lamb growth rate were positive and significant (P less than .05) up to 56 d of age. Growth rate was less closely associated with milk production for twin than for single lambs.     

TERMINATION OF EARLY PREGNANCY IN EWES BY USE OF A PROSTAGLANDIN ANALOGUE AND SUBSEQUENT FERTILITY

SUMMARY Of 87 Dorset ewes injected at 20 to 60 days of pregnancy with either 125 μg or 250 μg of the prostaglandin F^2α analogue, cloprostenol, 72 (83%) were detected in oestrus by teaser rams within 7 days. A total of 60 ewes mated with fertile rams 14 to 28 days after treatment and 36 of these (60%) subsequently lambed. Thirty-eight ewes mated with fertile rams 29 to 56 days after treatment and 30 of these (79%) subsequently lambed. The difference in fertility between the 2 periods was not significant.
Six additional ewes which did not respond to the cloprostenol lambed normally within 6 weeks. They were more than 100 days pregnant when treated.
In ewes which first exhibited oestrus by 7 days of treatment, plasma progesterone concentrations fell from near 4 ng/ml to 0.6 ng/ml within 48 h of treatment. In ewes not detected in oestrus progesterone concentrations did not decrease to similar low levels (1.4 ng/ml; t-test p < 0.005). Concentrations in the 6 ewes treated near 100 days of pregnancy dropped from 7.4 to 4.4 ng/ml over 48 h. Overall, the progesterone concentrations indicated that 92% of ewes treated at 20 to 60 days of pregnancy experienced rapid luteolysis in response to the cloprostenol.
There were no differences between the 2 doses of cloprostenol in the responses or subsequent fertility of the ewes.     

Performance of Polypay, Coopworth, and crossbred ewes: I. Reproduction and lamb production.

Six ewe genotypes, generated by mating Coopworth (C), Polypay (P), and Suffolk (S) rams to Polypay and Coopworth-type (Ct) ewes, were exposed to Hampshire rams for spring lambing from 1986 through 1990. Data from 1,092 exposures and 1,044 resultant lambings were used to analyze reproductive traits and lamb growth rates. Overall conception rate averaged 95% and ranged from 93% for S x Ct ewes to 97% for P x Ct ewes. Mean litter size at birth averaged 1.63 and ranged from 1.45 for C x C ewes to 1.75 for S x P ewes. Ewes from P dams had higher mean litter size (P less than .01) than those from Ct dams (1.73 vs 1.54), but differences between sire breeds were not significant. Incidence of lambing assistance was similar for ewes producing single or multiple lambs. Lamb birth weight influenced the level of assistance rendered to single-bearing but not to multiple-bearing ewes. Lambing assistance was not related to lamb survival, probably because the high surveillance level minimized trauma before assistance was rendered. Incidence of required assistance declined over subsequent parities. Lamb birth weights were affected by ewe genotype and increased with increasing ewe age. Survival of single-born lambs averaged 94% and was not affected by dam genotype. Survival of twins averaged 85%, ranging from 79% for lambs from S x Ct ewes to 89% for lambs from P x P ewes. Suffolk-sired ewes produced the heaviest mean birth and weaning weights for both singles and twins. Coopworth-sired ewes weaned heavier single lambs but lighter twins than P-sired ewes.     

Effect of season and lactation on postpartum fertility of Polypay, Dorset, St. Croix and Targhee ewes

The objective of this study was to compare rebreeding activities of spring- vs fall-lambing Polypay, Dorset, St. Croix and Targhee ewes that either suckled their lambs for 40 d or had lambs weaned at birth. Seasonal effects of male fertility were reduced by utilizing an excess number of fertile rams in the spring. Plasma concentrations of progesterone were monitored to assess days to the first normal ovulation, days to conception and estrous vs anestrous activity. Breed, season and lactation affected the rebreeding performance. Dorset ewes had similar conception rates between spring and fall but a shorter interval from lambing to first ovulation in the fall. Polypay and Targhee ewes were the opposite; they had higher conception rates in fall than in spring matings with no seasonal influence on postpartum interval. Postpartum ewes in the fall had higher conception rates, and fewer of these ewes became anestrous or had estrous cycles of abnormal duration than of those ewes lambing in the spring. Ewes that suckled for 40 d in the spring had delayed estrous activity, but when these ewes became estrual they had higher conception rates than ewes whose lambs were weaned at birth. Lactation had no inhibitory affect on the postpartum interval of fall lambing ewes. These data suggest that the response of different breeds to various components of postpartum fertility varies with season and management of the flock.     

Effects of intramuscular administration of recombinant bovine interferon-alpha I1 during the period of maternal recognition of pregnancy

One hundred ewes were utilized to determine the effects of interferon supplementation on the number of ewes pregnant and embryonic survival. Ewes were checked twice daily (0700 and 1600) for estrus using fertile rams. On d 12 through 16, ewes received twice-daily i.m. injections of either recombinant bovine interferon alpha I1 (2 mg IFN) or vehicle. Ewes remained penned with rams and were observed for subsequent estrous activity for at least 35 d after mating. To determine the number of fetuses and corpora lutea, all ewes were subjected to one surgery during mid-pregnancy (d 45 to 80). More (P less than .05) ewes were pregnant after treatment with IFN vs vehicle (45 of 49, 92% vs 37 of 49, 76%, respectively). The interestrous interval for ewes that were treated with IFN and did not conceive was longer (P less than .05) than for ewes given vehicle (26 +/- 1 vs 17 +/- 2 d, respectively). Embryonic survival (98.2 vs 87.9%; P less than .05), calculated as the number of fetuses present at the time of laparotomy and expressed as a percentage of the ovulation rate, and percentage of ewes with 100% fetal survival (96 vs 76%; P less than .05) were greater after treatment with IFN. It was concluded that supplementation of IFN increased both the number of ewes pregnant and embryonic survival.     

Synchronization of estrus and reproductive performance of ewes treated with synthetic progestogens administered by subcutaneous ear implant or by intravaginal sponge pessary

Experiments were conducted to compare the efficacy of synthetic progestogens administered by subcutaneous ear implant or intravaginal sponge to induce a synchronized estrus in adult ewes and ewe lambs and to evaluate reproductive performance (fertility and litter size) to breeding at the synchronized estrus. Experimental animals were representative of three strains maintained in total confinement and exposed to a synthetic light regimen which alternated at intervals of 4 mo from 18 h day length to 10 h day length/24 h. Treatments were applied at different times of the year at the end of a low light cycle. Implants contained Norgestomet (3 mg) impregnated in a polymethacrylate polymer (Implant H) or impregnated in a silastic polymer containing 1.05 (Implant S1), 1.78 (Implant S2) or 2.60 mg (Implant S3) Norgestomet, respectively. Intravaginal sponges contained 40 mg Fluorogestone Acetate. Implants or sponges were left in situ for 12 d and 500 IU pregnant mares' serum gonadotropin was injected im at the time of removal. Following treatment with Implant H, 96% of ewes were judged to be in estrus at 48 h after implant removal. Fertility of adult ewes and ewe lambs (6 to 7 mo of age at time of breeding) at the synchronized estrus were similar after implant H or sponge treatment, but litter size was higher (P less than .05) for adult ewes treated with sponges. The percentages of adult ewes marked by rams within 60 h after removal of silastic implants or intravaginal sponges were similar. There was a tendency for ewe lambs to be marked later than adult ewes and for adult ewes treated with Implant S1 and Implant S2 to be marked earlier than ewes treated with Implant S3 or sponges. Higher percentages (P less than .05) of adult ewes and ewe lambs lambed to breeding at the synchronized estrus after treatment with Implant S2 or Implant S3, respectively, than after treatment with Implants S2 or sponges.     

Variation in conception rates following synchronization of estrus with melengestrol acetate and prostaglandin F2 alpha

Beef cows and heifers (n = 263) at three locations that were exhibiting estrous cycle either were fed .5 mg/d melengestrol acetate (MGA) for 7 d and administered prostaglandin F2 alpha (25 mg, i.m.) on the last day of MGA feeding or were untreated. State of the estrous cycle at the beginning of the experiment was determined based on estrous detection and (or) progesterone concentrations in pretreatment blood samples. Estrous was checked twice daily for 30 d posttreatment. Animals were artificially inseminated approximately 12 h after detection of estrus. A synchronized estrus (less than 7 d posttreatment) was detected in 72% of the treated animals. More animals in the treated group became pregnant during the first 7 d of breeding, but their conception rate was lower than that of animals in the control group (P less than .05). Conception rate (36%) was reduced among treated animals when MGA feeding began late (d 14 to 20) in the estrous cycle. Conversely, the conception rate (66%) of treated animals fed MGA beginning earlier in the cycle was not different from that of control animals (73%; treatment x stage of cycle; P less than .05).     

Effects of ewe breed and ram exposure on estrous behavior in May and June

Two groups of purebred ewes (A and B), each consisting of 25 Dorsets and 25 Hampshires, were used to study effects of ewe breed and ram exposure on ovulation and estrus in May and June. Ewes lambed in January and February and were isolated from mature rams for at least 5 mo. From May 8 to June 11 (Period 1), Group A ewes were penned with vasectomized rams fitted with marking harnesses and Group B ewes were isolated from rams. From June 11 to July 13 (Period 2), rams were placed with Group B ewes and Group A ewes were isolated from rams. Ovulation was monitored by biweekly serum progesterone assays and crayon marks were used to detect estrus. For Group A ewes in Period 1, more Dorsets ovulated (96%) than did Hampshires (72%), and of ewes that ovulated, more Dorsets mated (83 vs 28%). Fifty-five percent of Dorsets, but only 20% of Hampshires, appeared to have been spontaneously cycling at the start of the experiment. Of ewes mated in Period 1, more Dorsets than Hampshires continued to cycle during Period 2 (65 vs 0%). For Group B ewes in Period 1, 44% of Dorsets, but only 8% of Hampshires, ovulated in the absence of rams. In Period 2, 92% of Dorsets and 84% of Hampshires ovulated. Of ewes that ovulated, more Dorset ewes mated (78 vs 52%). Of ewes that mated, more Dorsets appeared to be cycling spontaneously at ram introduction (39 vs 0%). Throughout the study, 24% of Dorsets, but no Hampshires, cycled continuously.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effectiveness of intravaginal progesterone inserts and FSH for inducing synchronized estrus and increasing lambing rate in anestrous ewes

The objectives of this study were to determine whether a new progesterone (P4)-releasing intravaginal insert would induce fertile estrus and whether FSH combined with the insert would increase prolificacy in anestrous ewes introduced to rams. Ewes of mixed breeding on six farms were assigned to four randomized treatments: control (C), n = 73; 12 d P4 (polycapralactone [PCL] insert with 0.82 g P4), (P12), n = 73; 12 d P4 plus i.m. FSH (Folltropin, 55 mg NIH-FSH-P1 equivalent) in propylene glycol, 24 h before insert removal, (P12F), n = 71; and 5 d P4 plus FSH (P5F), n = 77. Growth and ovulation of follicles were observed ultrasonographically in 20 ewes at four farms (five/treatment) at insert removal and 36, 48, 72, and 96 h later. Intact rams (1:15 ewes in multiple-sire groups) were joined at insert removal, and raddle marks were observed every 12 h for 5 d. On d 26 to 30, rams were removed; ewes were examined for pregnancy then and 20 d later. Percentage of ewes marked by rams was greater in P4-treated (66 to 79%) than in C (12%; P < 0.01) ewes and in P5F (79%) than in P12F (66%; P < 0.05). Diameters of largest follicles at insert removal were greater (P < 0.05) in P4-treated (5.5 +/- 0.2) than in C ewes (4.8 +/- 0.2). Progesterone increased numbers of follicles > 3 mm (P < 0.01) or ovulated (P < 0.05; 2.6 +/- 0.6 vs 1.3 +/- 0.6 in C ewes) and FSH increased number of follicles > 3 mm (P < 0.05). In FSH-treated ewes, ovulation rate tended to be greater after treatment with P4 for 5 than for 12 d (P = 0.09, 3.3 +/- 0.6 and 2.2 +/- 0.4, respectively). More P4-treated than C ewes lambed (P < 0.01) to the first (38 to 45 vs 0%) or both (63 to 66 vs 41%) service periods. Prolificacy (first service) did not differ between FSH-treated ewes (P12F + P5F; 1.8 +/- 0.1) and ewes treated with P4 only (P12; 1.6 +/- 0.1). However, FSH increased prolificacy to first service (1.8 +/- 0.1) over prolificacy to second service (C ewes 1.5 +/- 0.1; P < 0.05, and all ewes 1.4 +/- 0.1; P < 0.01). Pregnancy retention did not differ among treatments but was greater (P < 0.01) in ewes that conceived at the first (90.9 +/- 3.7) than at the second (72.5 +/- 3.3) service period. In conclusion, a PCL insert in combination with ram introduction at insert removal was more effective than ram introduction alone to induce synchronized estrus and ovulation and to yield pregnancy after one or two service periods. Treatment with P4 for 5 d was as effective as for 12 d to induce fertile estrus in FSH-treated anestrous ewes.     

Progesterone plus PMSG Priming in seasonally anovulatory lactating Sarda ewes exposed to the ram effect

The aim of this trial was to evaluate the effectiveness (fertility and lambing) of priming with a single injection of progesterone plus PMSG in anovulatory lactating Sarda ewes subjected to the ram effect (RE) in spring. Thirty ewes (P4 group) were i.m. injected with 30 mg progesterone and 500 IU PMSG 36 h before ram introduction (d 0). This treatment was compared to a 12-day treatment with fluorogestone acetate intravaginal sponges that was followed by injections of 350 IU PMSG upon sponge withdrawal (FGA group, n=30). All ewes responded to RE, showing plasma progestrone concentrations >1 ng/mL between d 6 and 12 (FGA) or 6 and 9 (P4). Eighty-nine percent of the P4 ewes conceived at first ovulation, and 11% conceived following a short estrus cycle. Lambings occurred on d 150.4 +/- 3.9, and the lambing rate was 100%. The fertility of the FGA ewes was 83% for the induced ovulation and was 7% for the second ovulation after a normal cycle. The FGA ewes lambed on d 149.8 +/- 4.4, and the lambing rate was 83%. Two abortions were recorded for the FGA ewes, which had higher prolificacy than the P4 group (2.2 +/- 0.8 vs. 1.8 +/- 0.4, respectively; P<0.05). Both fertility and the lambing rate were high in both groups, with a high degree of estrus synchronization, and there were no significant differences between the groups. We concluded that priming of lactating Sarda ewes in spring with P4+PMSG before RE is an effective and competitive method (cheaper and more practical than FGA+PMSG) of inducing fertile ovulations in these ewes.     

Poor reproductive response of anestrous Suffolk ewes to ram exposure is not due to failure to secrete luteinizing hormone acutely

Twenty Polypay-sired ewes (Group P) and 14 Suffolk ewes (Group S) were bled at 48-h intervals for 10 d beginning on April 6, 1989, and the serum was assayed for progesterone to determine which ewes were anestrous; 9/20 Group P ewes were anestrous, compared with 14/14 Group S ewes (P less than .001). Catheters were placed into the jugular vein of anestrous ewes from both breed groups (eight of Group P, seven of Group S), and samples of serum were collected at 12-min intervals for 4 h. Then, the ewes were exposed to mature, intact rams, and additional samples were taken at 12-min intervals for 4 h after ram exposure. The serum was later analyzed to determine the secretion of LH in response to ram introduction. After the acute bleeding period, all Group P and Group S ewes were commingled and exposed to a ram continuously for 42 d. Samples of serum were collected thrice weekly and analyzed for progesterone to monitor ovulatory response to ram introduction through the 42-d period. In addition, breeding activity and lambing data were recorded. When all Group P ewes were compared to Group S ewes, a greater proportion (P less than .001) of Group P ewes were mated (20/20 vs 3/13; one Group S ewe died during the 42-d mating period) by the end of the 42-d period and more (P less than .001) ewes lambed in the fall (17/20 Group P vs 2/13 Group S).(ABSTRACT TRUNCATED AT 250 WORDS)