Experimental use of prostaglandin F2 alpha to synchronize estrus in cattle]

Experiments were conducted for the use of prostaglandin to synchronise oestrus in dairy cows. One single dose of 5 mg F2-Alpha prostaglandin was administered via the intrauterine route. The reference values of the control groups were matched by first insemination following induced oestrus among the best of the test animals which were inseminated twice. These values reached 72 and 96 hours following application accounted for 46.7 and 50.0 per cent. The yellow body phase, a prerequisite for oestrus production by prostaglandins, had been induced in the test animals by cycle blocking, using gestagen. Possible use of the method in a bio-engineering context for large-scale oestrus synchronisation in cows is discussed.     

Use of prostaglandin F2 alpha in the treatment of unobserved estrus in lactating dairy cattle

A field trial was conducted to evaluate the use of prostaglandin F2 alpha (PGF2 alpha) (lutalyse)a in lactating dairy cattle with unobserved estrus in the presence of a functional corpus luteum (CL) and clinically normal reproductive tract. Seventy-three Holstein and 9 Jersey cows, weighing between 340.0 and 772.7 kg, were allotted to treatment and control groups. All treated cows were inseminated within 80 hours after treatment as assigned by this trial. Control cows were inseminated at the first observed estrus. Of the treated cows, 50% showed estrus within 80 hours after treatment. In this trial, 96% of the treated cows and 92% of the control cows were determined to have at least 1 functional CL on the day of treatment. For the treatment group and the control group, mean serum progesterone concentrations were 4.1 ng and 3.5 ng (P less than 0.2, by Student's t test), respectively, on day of treatment and were 0.4 ng and 5.0 ng (P less than 0.005, by Student' t test) on day 5 after treatment. Pregnancy rates were 57% for treated and 47% for control cows (P = 0.5, by X2). Days from treatment to first-observed estrus, treatment to first service, and treatment to conception were significantly reduced in the treatment group compared with these criteria for the control group (P less than 0.05, 0.005, and 0.01 respectively). It was concluded that induction of luteolysis with PGF2 alpha in lactating dairy cattle with unobserved estrus and a palpable functional CL will be an effective addition to reproductive health programs.     

Termination of pseudopregnancy by administration of prostaglandin F2alpha and termination of early pregnancy by administration of prostaglandin F2alpha or colchicine or by removal of embryo in mares.

At day 24 of gestation, pregnant mares were allotted to 1 of 5 treatment groups (3 to 5 mares/group): group A--nontreated controls; group B--intraembryonic injection of 4 mg of colchicine on day 24; group C--removal of embryo on day 24; group D--subcutaneous injection of 1.25 mg of prostaglandin F2alpha (PGF2alpha) on day 32; and group E--removal of embryo on day 24 and subcutaneous injection of PGF2alpha on day 32. In all mares treated with colchicine (group B), the fetal bulge was absent within 2 days. The interval from injection of colchicine to onset of estrus was very short (mean, 4 days). These results indicated that treatment with colchicine was lethal to the 24-day embryo, and pseudopregnancy did not occur. Surgical removal of the embryo (group C) resulted in pseudopregnancy characterized by a prolonged interval from treatment to return to estrus (mean, greater than 31 days), prolonged production of progesterone, and prolonged maintenance of tense uterine and cervical tone. The interval from treatment to ovulatory estrus was longer (P less than 0.05) for group C mares than for group B mares. The mean interval from treatment to complete loss of tense tubular uterine tone was not significantly different between group A pregnant controls (28.3 days) and group C pseudopregnant mares (30 days). Treatment of pregnant mares (group D) with a single injection of PGF2alpha on day 32 resulted in loss of pregnancy in 4 of 4 mares within 2 to 5 days, and in all group D mares a large decrease in progesterone concentration occurred on day 33, 34, or 35. Although subsequent reproductive activity was variable, all group D mares rapidly lost the tense uterine and cervical tone characteristic of early pregnancy. These results indicated that a single subcutaneous injection of 1.25 mg of PGF2alpha caused loss of pregnancy, and pseudopregnancy did not occur. Treatment of group E mares, which had been made pseudopregnant by removal of embryo, with 1.25 mg of PGF2alpha resulted in termination of pseudopregnancy in 5 of 5 mares. All group E mares returned to estrus within 2 to 5 days after treatment, and progesterone concentration decreased (P less than 0.05) within 2 days after treatment. There was no significant difference in loss of tense tubular uterine or cervical tone between pregnant (group D) and pseudopregnant (group E) mares after PGF2alpha treatment.     

Synchronization of estrus in postpartum beef cows with melengestrol acetate and prostaglandin F2 alpha

At the beginning of the breeding season, most beef herds consist of a population of cyclic and anestrous postpartum cows. To be most effective and economical, an estrous synchronization method for postpartum beef cows must be capable of synchronizing estrus in cyclic cows and inducing estrus in anestrous cows. In the first of two experiments, the combination of melengestrol acetate (MGA) fed for 9 d and prostaglandin F2 alpha (PGF2 alpha) administered on the last day of MGA feeding synchronized estrus in cyclic cows (94%) and induced estrus in anestrous cows (66%) as effectively as combining PGF2 alpha with a progestin implant (97 and 75%, respectively). In the second experiment, MGA treatment was necessary for 7 d prior to administering PGF2 alpha to maximize the expression of estrus in cyclic and anestrous cows. In both experiments the proportion of cows exhibiting a synchronized estrus and the pregnancy rates tended to be higher for cows that were cyclic prior to treatment. However, the MGA-PGF2 alpha treatments consistently induced estrus in more than 50% of the anestrous cows and approximately one-third of the cows that were anestrous prior to treatment conceived during the synchronized breeding period. The MGA-PGF2 alpha treatment was 33 to 46% less expensive than a comparable estrous synchronization method that is approved by the U.S. Food and Drug Administration. If feeding MGA and administering PGF2 alpha is approved, it may be the treatment of choice for synchronizing estrus in cyclic cows and inducing estrus in anestrous cows when supplemental feeding is feasible.     

Effect of prostaglandin F2 alpha administration on early pregnancy in ewes

Two trials were conducted with ewes to determine the effects of prostaglandin F2 alpha (PGF) administration during the first week of gestation. In trial 1, ewes (n = 134) were checked for breeding activity once daily and half of them received 10 mg PGF im at either 0, 24, 48, 72, 96, 120 or 144 h after detection of a breeding mark. The other half served as uninjected controls. In trial 2, ewes (n = 153) were checked for breeding activity twice daily. Two-thirds of the ewes received 10 mg PGF at either 24, 36, 48, 60, 72, 84, 96, 108, 120 and 132 h following detection of a breeding mark. The other one-third of the ewes served as uninjected controls corresponding to treatment times of 24, 48, 72, 96 or 120 h. In trial 1, the percentage of ewes lambing as a result of first service decreased as time of administration of PGF increased. The first-service pregnancy rate was 87.5% for ewes given PGF at 0 h and 0% for ewes given PGF at 144 h. Fewer (P less than .05) ewes given PGF at 96, 120 or 144 h after first mating lambed than control ewes. Similarly in trial 2, fewer (P less than .05) ewes given PGF at 96, 108, 120 or 132 h after first mating lambed than did controls. The total number of ewes lambing as a result of the entire breeding season did not differ (P greater than .05) between treated and control ewes in trial 1 (88.2 vs 87.3%) or trial 2 (85.7 vs 83.3%).(ABSTRACT TRUNCATED AT 250 WORDS)     

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).     

Synchronization of estrus with melengestrol acetate and prostaglandin F2 alpha in beef and dairy heifers

Beef (n = 783) and dairy (n = 209) heifers at 14 locations were used to evaluate the efficacy of feeding melengestrol acetate (MGA; .5 mg/d) for 7 d followed by an i.m. injection of 25 mg prostaglandin F2 alpha (PGF) on the last day of MGA feeding (MGA + PGF) to synchronize estrus. Untreated heifers (C) and heifers injected once i.m. with PGF served as contemporary controls. Heifers were observed for estrual behavior for a minimum of 38 d starting on the 2nd d of MGA feeding. Heifers in estrus from d 1 through d 60 after PGF injection were artificially inseminated (AI) or bred to bulls (d 30 to 60 post PGF only). During the 7-d MGA feeding period fewer (P less than .01) MGA + PGF (1.5%) than C (20.6%) or PGF (18.1%) heifers were observed in estrus. Percent of heifers in estrus d 1 to 6 post PGF was different among groups (P less than .05; 30.5, 52.8, 72.3 for C, PGF and MGA + PGF, respectively). More (P less than .01) MGA-fed (92%) than non-MGA-fed (C and PGF combined) heifers (85.4%) were observed in estrus during d 1 to 24. Conception rate (CR) during d 1 to d 6 was not different (P = .19) between C (58.9%) and MGA + PGF (51.2%) heifers; CR was lower (P = .01) for MGA + PGF than for PGF (68.3%) heifers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effectiveness of GnRH plus prostaglandin F2alpha for estrus synchronization in cattle of Bos indicus breeding

Postpartum and lactating crossbred cows containing a percentage of Bos indicus breeding at three locations were studied to determine the efficacy of GnRH + PGF2alpha combinations for synchronization of estrus and(or) ovulation. Cows were equally distributed to each of three treatments by body condition score at the start of the experiment (d 0). All cows received 100 microg of GnRH on d 0 and 25 mg of PGF2alpha 7 d later. The three insemination protocols included 1) AI 12 h after exhibiting estrus during d 7 to 12 of the experiment (Select-Synch; n = 197); 2) timed-AI + 100 microg of GnRH on d 9 of the experiment (CO-Synch; n = 193); 3) AI 12 h after exhibiting estrus during d 7 to 10 of the experiment. Cows not exhibiting estrus by d 10 were timed-AI and injected with 100 microg of GnRH on d 10 of the experiment (Hybrid-Synch; n = 200). The percentage of cows exhibiting estrus during d 7 to 12 of the experiment was lower (P < 0.05) for CO-Synch (17.6%) cows than for Select-Synch or Hybrid-Synch (45.2 and 33.0%, respectively) cows, which did not differ (P > 0.05). For the Select-Synch and Hybrid-Synch cows that exhibited estrus during d 7 to 10 of the experiment and were artificially inseminated, conception rates were similar across treatments (50.5%). Pregnancy rates were greater (P < 0.01) for CO-Synch and Hybrid-Synch (31.0 and 35.5%, respectively) cows than for Select-Synch (20.8%) cows. A greater (P < 0.01) percentage of cycling cows became pregnant (34.5%) than noncycling cows (25.9%) across all treatments. The CO-Synch and Hybrid-Synch synchronization protocols resulted in greater pregnancy rates compared with the Select-Synch protocol in postpartum and lactating crossbred cows containing a percentage of Bos indicus breeding.     

Behavioral responses of periparturient sows and juvenile pigs to prostaglandin F2 alpha

Within minutes after prostaglandin F2 alpha (PGF2 alpha) injection on d 112 postcoitum and again in the last few hours before delivery of the first piglet around 22 h later, sows in pens intensely rooted and pawed, which is typical prepartum nestbuilding behavior. Control sows engaged in most such typical prepartum activity (TPA) within 16 h before delivery. The overall frequencies and durations of TPA for the 48-h prepartum period were not influenced by injection, but injection of PGF2 alpha did alter the temporal pattern of behavior and resulted in a bimodal profile of activity. The PGF2 alpha injected 24 h postpartum immediately induced TPA in sows, but it was less intense and shorter than prepartum TPA. Postpartum only, some PGF2 alpha sows rubbed or kicked at their abdomens and seemed to experience discomfort. Because PGF2 alpha elicited TPA both pre- and postpartum, TPA probably was not directly triggered by changes in plasma progesterone concentration or in the estrogen:progesterone ratio. After injection of .5 or 1 mg PGF2 alpha, prepubertal pigs (approximately 10 kg) lay more but also changed posture more often. After PGF2 alpha, slight or no TPA was seen, but pigs pawed more often, showed signs of abdominal discomfort, defecated more often, stretched and arched their backs and scratched or kicked at their sides or abdomens. Most PGF2 alpha-induced TPA by prepartum sows probably is not caused by some general peripheral effect, but rather by some neural or endocrine change that stimulates nestbuilding specifically in animals primed by the endogenous endocrine environment of late pregnancy.     

Pregnancy and peripheral plasma progesterone levels in cows inseminated after synchronization of estrus with prostaglandin F2 alpha

Fifteen Holstein cows were treated with two doses of 25 mg of a prostaglandin F₂α (PGF₂α as dinoprost tromethamine) administered intramuscularly 11 days apart. The cows were then divided into three groups and inseminated either at 72, 80 or 72 and 96 hours after the second dose of PGF₂α. Thirteen cows ovulated after the second prostaglandin treatment. Eight cows were diagnosed pregnant by rectal palpation 42 days after insemination but only five calved. PGF₂α induced luteolysis in cows with active corpora lutea as evidenced by the dramatic decreases in the plasma progesterone concentrations after treatment. In contrast, following PGF₂α administration to cows in follicular or late luteal phase the concentrations of plasma progesterone either increased gradually or remained low for several days before increasing to maximal levels. The ovulatory rate after the two doses of PGF₂α11 days apart was high. However, the pregnancy rate after this treatment was influenced by other factors including abnormal ovarian function.     

Control of estrus with prostaglandin F2alpha in mares: minimal effective dose and stage of estrous cycle.

To determine the minimal effective dose of prostagiandin (PGF2alpha; tromethamine salt) given subcutaneously (SC), mares of mixed breeding (400 kg av body weight) were given 2-, 3-, 5-, and 10-mg doses from 7 to 9 days after ovulation. In some but not all mares given doses of 2 and 3 mg of PGF2alpha, luteolysis occurred, but doses of 5 or 10 mg of PGF2alpha were luteolytic in all mares. The 10-mg dose of PGF2alpha did not cause luteolysis in mares 1 day after ovulation, and caused luteolysis in only 2 of 5 mares on day 3 after ovulation. The same dose of PGF2alpha, however, caused luteolysis in all mares on days 5 or 7 after ovulation. The results indicate that the minimal effective luteolytic dose of PGF2alpha (free-acid equivalent) is about 9 mug/kg, and that PGF2alpha is effective fromday 5 after ovulation.     

Technical note: use of slow-release estradiol and prostaglandin F2alpha to induce pseudopregnancy and control estrus in gilts

We determined whether a single injection of slow-release estradiol-17beta (SRE2) would induce pseudopregnancy in gilts and whether PGF2alpha would regress the corpora lutea (CL) of pseudopregnancy. Crossbred gilts (n = 40) were induced to ovulate by treatment with 400 IU of hCG + 200 IU of eCG (PG600, Intervet, Millsboro, DE) given at 180 d of age (d = 0). On d 14, gilts were injected i.m. with one of five doses (n = 8 gilts/dose) of SRE2 (0, 12.5, 25, 50, or 100 mg). Blood samples were collected before SRE2 and twice weekly until d 73 to monitor serum progesterone (P4) and estradiol (E2). On d 59, gilts received (i.m.) 10 mg of PGF2alpha (Lutalyse, Pharmacia Upjohn, Kalamazoo, MI) and were checked for estrus for 7 d. On d 62, mammary development was scored (0 = no development; 1 = some development; 2 = teat and gland development) by a neutral observer. Treatment with SRE2 increased (P < .05) peak E2 concentrations, duration of luteal function, and mammary gland score. There were no differences (chi-square, P > .05) among doses of SRE2 in the percentage of pseudopregnant gilts that showed luteolysis after PGF2alpha. We conclude that a single injection of SRE2 can induce pseudopregnancy and that the CL can be regressed with PGF2alpha, providing a simple method for controlling estrus in gilts.     

Synchronization of estrus and artificial insemination in replacement beef heifers using gonadotropin-releasing hormone, prostaglandin F2alpha, and progesterone

We evaluated whether a fixed-time AI (TAI) protocol could yield pregnancy rates similar to a protocol requiring detection of estrus, or detection of estrus and AI plus a clean-up TAI for heifers not detected in estrus, and whether adding an injection of GnRH at controlled internal drug release (CIDR) insertion would enhance fertility in CIDR-based protocols. Estrus in 2,075 replacement beef heifers at 12 locations was synchronized, and AI was preceded by 1 of 4 treatments arranged as a 2 x 2 factorial design: 1) Estrus detection + TAI (ETAI) (n = 516): CIDR for 7 d plus 25 mg of prostaglandin F2alpha (PG) at CIDR insert removal, followed by detection of estrus for 72 h and AI for 84 h after PG (heifers not detected in estrus by 84 h received 100 microg of GnRH and TAI); 2) G+ETAI (n = 503): ETAI plus 100 microg GnRH at CIDR insertion; 3) Fixed-time AI (FTAI) (n = 525): CIDR for 7 d plus 25 mg of PG at CIDR removal, followed in 60 h by a second injection of GnRH and TAI; 4) G+FTAI (n = 531): FTAI plus 100 microg of GnRH at CIDR insertion. Blood samples were collected (d -17 and -7, relative to PG) to determine ovarian status. For heifers in ETAI and G+ETAI treatments, a minimum of twice daily observations for estrus began on d 0 and continued for at least 72 h. Inseminations were performed according to the a.m.-p.m. rule. Pregnancy was diagnosed by transrectal ultrasonography. The percentage of heifers exhibiting ovarian cyclic activity at the initiation of treatments was 89%. Pregnancy rates among locations across treatments ranged from 38 to 74%. Pregnancy rates were 54.7, 57.5, 49.3, and 53.1% for ETAI, G+ETAI, FTAI, and G+FTAI treatments, respectively. Although pregnancy rates were similar among treatments, a tendency (P = 0.065) occurred for pregnancy rates in the G+ETAI treatment to be greater than in the FTAI treatment. We concluded that the G+FTAI protocol yielded pregnancy rates similar to protocols that combine estrus detection and TAI. Further, the G+FTAI protocol produced the most consistent pregnancy rates among locations and eliminated the necessity for detection of estrus when inseminating replacement beef heifers.     

Effects of uterus and prostaglandin F2alpha on corpora lutea in Mongolian gerbils and guinea pigs.

One or both uterine horns were removed on postpartum day 6 day 1=parturition in pseudopregnant gerbils. On dy 16, the corpora lutea (C) in unilaterally hysterectomized gerbils were smaller (P less than 0.05) in the ovary adjacent to an intact horn than in the ovary adjacent to a removed horn. The cL were smaller in uterine-intact than in completely hysterectomized gerbils. I n another experiment, the cl were smaller (P less than 0.05) in pseudopregnant gerbils given a single intrauterine injection of a 30- or 20-mug dose of prostaglandin F2alpha) (PGFalpha) on postpartum day 6 and theen necropsied on day 10 than in gerbils given 10-, 5-, 1-, and 0-mug doses; CL were smaller (P less than 0.05) on the side ipsilateral to the treated horn than on the opposite side, although the interaction of dose and side was not significant...