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PubMed1999

Synchronization of estrus in beef cattle with norgestomet and estradiol valerate.

Fifty-six cows received a norgestomet implant and an injection of norgestomet and estradiol valerate; half (n = 28) received 500 IU equine chorionic gonadotrophin (eCG) at implant removal, 9 d later. A third group (n = 25) received 2 doses of cloprostenol (500 micrograms) 11 d apart. Estrous rate was higher (P < 0.05) for cows given norgestomet and estradiol plus 500 IU eCG (75.0%) than for those receiving cloprostenol (44.0%); for those receiving norgestomet and estradiol alone, it was intermediate (67.8%). Pregnancy rates to artificial insemination (after estrus or timed) were higher (P < 0.05) for cows given norgestomet and estradiol than for those given cloprostenol (23 of 28, 82.1% vs 13 of 25, 52.0%), and intermediate (67.8%) for those given norgestomet and estradiol plus eCG. In a second experiment, for heifers treated with norgestomet and estradiol plus eCG (n = 15) or with 2 doses of cloprostenol (n = 16), estrous rates were 66.7% vs 56.2% (P > 0.5), ovulation rates were 100.0% vs 81.2% (P = 0.08), intervals from implant removal or cloprostenol treatment to estrus were 48.0 +/- 4.4 hours vs 61.3 +/- 7.0 hours (P = 0.12) and to ovulation were 70.4 +/- 4.4 hours vs 93.2 +/- 7.5 hours (P < 0.01), respectively; pregnancy rates were 41.7 and 35.7%, respectively (P > 0.5). Norgestomet and estradiol were as good as (heifers) or superior to (cows) a 2-dose cloprostenol regimen. In cows given norgestomet and estradiol, injecting eCG at implant removal did not significantly improve estrous or pregnancy rates.

Analysis of Variance↗
PubMed1992

Synchronization of estrus in dairy goats given norgestomet and estradiol valerate at various stages of the estrous cycle.

Dairy goats were given subcutaneous implants with 3 mg of norgestomet (NOR) and IM injections of 0.625 mg of estradiol valerate and 0.375 mg of norgestomet on day 0 of the estrous cycle (estrus; NOR 0, n = 18), on postestrus day 4 (NOR 4, n = 18), or on postestrus day 11 (NOR 11, n = 15). Ear implants were removed after 9 days. Mean (+/- SE) hours from removal of ear implants to onset of estrus and proportion of goats responding were 36 +/- 3.8 and 83%, 33 +/- 4.0 and 61%, and 36 +/- 2.7 and 93% for groups NOR 0, NOR 4, and NOR 11, respectively. There were no significant differences between treatment groups in time to onset of estrus. The percentage of goats in group NOR 11 that had signs of estrus was significantly greater than the percentage of goats in group NOR 4. Of the goats in groups NOR 0, NOR 4, and NOR 11 that had signs of estrus, 53, 55, and 86%, respectively, had onset of behavioral estrus between 24 and 48 hours after implant removal. All goats that had signs of estrus had onset of behavioral estrus between 12 and 72 hours after implant removal. Mean (+/- SE) hours from removal of ear implants to time of peak concentrations of luteinizing hormone (LH) were 49 +/- 4.1, 49 +/- 3.8, and 49 +/- 4.0 for groups NOR 0, NOR 4, NOR 11, respectively (not different). The percentage of goats in group NOR 11 that had LH peaks was significantly greater than the percentage of goats in group NOR 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Synchronization of estrus in dairy goats treated with prostaglandin F at various stages of the estrous cycle.

Dairy goats were given IM injections of 125 micrograms of cloprostenol sodium on day 6 of the estrous cycle (prostaglandin F [PGF] 6, n = 22) or day 12 of the estrous cycle (PGF 12, n = 26). Mean +/- SE hours from injection to onset of behavioral estrus and proportion of goats responding were 46 +/- 4.2 (range, 12 to 88 hours) and 95% and 48 +/- 2.9 (range, 34 to 68 hours) and 100% for groups PGF 6 and PGF 12, respectively. There was no significant difference between the groups in mean time to onset of estrus, but variances about the means were different. Of the does in groups PGF 6 and PGF 12, 67 and 85%, respectively, had signs of onset of estrus between 36 and 60 hours after administration of PGF. Mean (+/- SE) hours from injection to time of peak concentrations of luteinizing hormone (LH) were 62 +/- 3.1 and 64 +/- 2.1 for groups PGF 6 and PGF 12, respectively. Of the does in groups PGF 6 and PGF 12, 86 and 100%, respectively, had LH peaks. Of the does in groups PGF 6 and PGF 12, 68 and 77%, respectively, had peak concentrations of LH between 48 and 72 hours after administration of PGF. All does in groups PGF 6 and PGF 12 had concentrations of progesterone greater than or equal to 1.0 ng/ml on the day of administration of PGF. Concentrations decreased to less than 1.0 ng/ml by 48 hours after injection in all does except 1 in group PGF 6.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

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 F(2)alpha (PGF(2)alpha 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 PGF(2)alpha. Thirteen cows ovulated after the second prostaglandin treatment. Eight cows were diagnosed pregnant by rectal palpation 42 days after insemination but only five calved. PGF(2)alpha induced luteolysis in cows with active corpora lutea as evidenced by the dramatic decreases in the plasma progesterone concentrations after treatment. In contrast, following PGF(2)alpha 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 PGF(2)alpha11 days apart was high. However, the pregnancy rate after this treatment was influenced by other factors including abnormal ovarian function.

Animals↗
PubMed1980

[Sex hormones in young pigs. I. Concentrations of plasma progesterone and estrogens of sows and urinary estrogens after synchronization of estrus and ovulation].

Treatment for synchronised heat and ovulation, using Suisynchron-Prämix, Bernburg, pregnant-mare serum gonadotrophin (PMSG), and human chorionic gonadotrophin (HCG), was followed with twelve gilts by daily measurement over 31 days of urine oestrogens, plasma progesterone as well as of plasma oestrogens during the oestric phases. Hormonal developments recorded during the oestrus and luteum phases were in agreement with the concepts and data so far known for the subject. An intermediate peak of oestrogen concentration was clearly recordable in the di-oestrus, that is between the tenth and 15th days of cycle. Its physiological importance will have to be further investigated.

Animals↗
PubMed1977

[Use of megesterol acetate for synchronization of estrus in cows].

Megestrol acetate has proved to be of positive impact upon synchronisation of oestrus in beef cows. Fodder-borne administration of 35-45 mg megestrol acetate caused oestrus in nursing cows, accompanied by disorders in ovarian function. The physiological condition of the animal at the date of treatment was found to be of major relevance to success. Evidence was produced to the strong action of serum obtained from pregnant mares in which the ratio of total gonadotrophic activity to luteinising activity was between 3:1 and 2.5:1. The use of megestrol acetate is recommended as a method by which to activate sexual function in the context of beef cattle breeding.

Animals↗
PubMed1995

Evaluation of the effects of route of administration of cloprostenol on synchronization of estrus in diestrous dairy cattle.

Cloprostenol was administered IV or IM to diestrous dairy cows to study luteolysis and synchrony of estrus and ovulation. In Study 1, 28 Holstein cows were assigned to receive injections of cloprostenol, IV or IM, on day 8 or 10 of the estrous cycle. Differences in cloprostenol-induced luteolysis or interval to estrus, were not detected. Ultrasonography revealed that 2 cows treated IV on day 8, 1 cow treated IM on day 8, and 2 cows treated IV on day 10 did not ovulate despite evidence of an apparently normal estrus. In Study 2, 20 Holstein cows were assigned to receive cloprostenol injections, IV or IM, on day 10 of the estrous cycle. Interval to estrus was not affected by route of administration. Analysis of these data indicated that cloprostenol given IV did not alter luteolysis or improve synchrony of estrus and ovulation when compared with cloprostenol given IM.

Animals↗
PubMed2004

Methods to reduce or eliminate detection of estrus in a melengestrol acetate-PGF2alpha protocol for synchronization of estrus in beef heifers.

Three experiments were conducted to evaluate methods to decrease or eliminate the detection of estrus inherent to a melengestrol acetate (MGA)-PGF2alpha (PGF) protocol for synchronization of estrus in heifers. In each experiment, all heifers received 0.5 mg of MGA x animal(-1) x d(-1) for 14 d (d -32 to -19) and PGF (25 mg, i.m.; d 0, 0 h) 19 d after the last feeding of MGA (MGA-PGF protocol). In Exp. 1, heifers (n = 709) were assigned to each of the following protocols: 1) the MGA-PGF protocol with AI 6 to 12 h after detection of estrus (estrus AI; MGA-PGF); 2) MGA-PGF plus 100 microg, i.m. of GnRH on d -7 (1x GnRH) and estrus AI; or 3) MGA-PGF, GnRH on d -7, and GnRH (100 microg, i.m.) at 48 h after PGF, coincident with insemination (2x GnRH-TB48). In Exp. 2, heifers (n = 559) received the MGA-PGF protocol and were inseminated by either estrus AI or fixed-time AI (TAI) at 60 h, coincident with an injection of GnRH (GnRH-TB60). In Exp. 3, all heifers (n = 460) received the MGA-PGF protocol and were inseminated by estrus AI when detected up to 73 h. Heifers not observed in estrus by 73 h received TAI between 76 and 80 h. Half the heifers inseminated by TAI received no further treatment (TB80), and the remaining half was injected with GnRH at insemination (GnRH-TB80). Variance associated with the interval to estrus and the proportion in estrus from d 0 to 5 was similar for 1x GnRH and MGA-PGF treatments in Exp. 1. Pregnancy rate (d 0 to 5) did not differ for the MGA-PGF and 1x GnRH treatments (62.5 and 60.4%, respectively), and both were greater (P < 0.05) than TAI pregnancy rate in the 2x GnRH-TB48 treatment (42.3%). In Exp. 2, the peak estrous response occurred 60 h after PGF. Pregnancy rate during the synchrony period was greater (P < 0.05) for the MGA-PGF (255/401; 63.6%) than the GnRH-TB60 (74/158; 46.6%) treatment. In Exp. 3, 75.7% of heifers (348/460) were detected in estrus by 73 h and were inseminated, with a conception rate of 74.4%. Pregnancy rates after TAI did not differ between TB80 and GnRH-TB80 (14/56 = 25% and 19/ 56 = 33.9%, respectively). Total pregnancy rate was 63.5% for heifers inseminated after detected estrus and by TAI. Collectively, these data indicate that the exclusive use of TAI for heifers treated with the MGA-PGF protocol resulted in lower pregnancy rates than when AI was performed after detection of estrus. However, estrus AI for 3 d and TAI at the end of d 3 could result in pregnancy rates similar to those achieved after a 5-d period of detecting estrus.

Animals↗
PubMed1991

[Estrus and ovulation synchronization in Merino meat sheep. 1. Effect of Gonavet "Berlin Chemie" after estrus synchronization with prostaglandin F2 alpha in Merino meat sheep].

Oestrus synchronisation by means of PGF2 alpha analogues was followed by injection of Gonavet "Berlin-Chemie" which triggered off an LH peak, 2 to 3 hours from injection. Injection of Gonavet "Berlin-Chemie", 44 hours after PGF2 alpha application, caused synchronisation of all LH peaks. The interval between injection of Gonavet "Berlin-Chemie" and onset of ovulation amounted to 22 hours. The length of ovulation was not accurately determinable. Ovulation was successfully induced to all sheep by application of Gonavet "Berlin-Chemie", 44 or 48 hours after PGF2 alpha injection. Ovulation rates were 1.75 or 1.54. Luteolytic action on sheep of Cloprostenol "Jenapharm", a PGF2 alpha analogue, proved to be just as good as that of Oestrophan (SPOFA).

Animals↗
PubMed2004

Follicular dynamics and steroid profiles in cows during and after treatment with progestin-based protocols for synchronization of estrus.

Two progestin-based protocols for the synchronization of estrus in beef cows were compared. Cyclic, nonlactating, crossbred, beef cows were assigned by age and body condition score to one of two treatments. Cows assigned to the MGA Select protocol were fed melengestrol acetate (MGA; 0.5 mg x cow(-1) x (-1)) for 14 d, GnRH was administered (100 microg i.m. of Cystorelin) 12 d after MGA withdrawal, and PGF2alpha (25 mg of i.m. Lutalyse) was administered 7 d after GnRH. Cows assigned to the 7-11 Synch protocol were fed MGA for 7 d and were injected with PG on d 7 of MGA, GnRH on d 11, and PG on d 18. Transrectal ultrasonography was performed daily to monitor follicular dynamics from the beginning of MGA feeding through ovulation after the synchronized estrus. All cows exhibited estrus in response to PG. Mean interval to estrus was shorter (P < 0.01) for 7-11 Synch-treated cows (56 +/- 1.5 h) than for cows assigned to the MGA Select protocol (73 +/- 4.7 h). Mean interval from estrus to ovulation did not differ between treatments (P > 0.10). Variances for interval to estrus differed (P < 0.01) between treatments. Mean follicular diameter at GnRH injection, PG injection, and estrus did not differ (P > 0.10) between treatments. Relative to MGA Select, serum estradiol-17beta concentrations were higher (P < 0.01) for 7-11 Synch 2 d and 1 d before, on the day of GnRH injection, in addition to 4 d after GnRH, and 24 h after PG. Mean progesterone concentrations were greater (P < 0.01) for MGA Select cows from 4 d before to 7 d after GnRH. Forty-four percent of the variation in interval to estrus between treatments was explained by differences in estradiol-17beta concentrations 24 h after PG. This study suggests that follicular competence is likely related to steroidogenic capacity of the follicle and the endocrine environment under which growth and subsequent ovulation of the dominant follicle occurs.

Age Factors↗
PubMed1987

Dairy herd reproductive management programs with or without synchronization of estrus.

Reproductive efficiencies were compared among herds with (treated, n = 25) or without (visited control, n = 25) routine synchronization of estrus and herds without investigator visits (unvisited control, n = 22). Treatment groups were subdivided based on participation in veterinary herd health programs. Reproductive tracts were palpated rectally at 21-d intervals for 6 mo in two sets of treated and visited control herds. Data were collected during the visitation period and from the 6-mo period before visits. In treated herds, cows more than 40 d postpartum with a corpus luteum received prostaglandin F2 alpha. In visited control herds, cows received prostaglandin F2 alpha after 82 d postpartum if they were not observed in estrus. Routine synchronization of estrus did not enhance herd reproductive efficiency compared with no synchronization of estrus in visited herds. Small changes in reproductive efficiency occurred during visits in herds with an established reproductive health program. However, herds not using a health program had 15.2 fewer d from calving to insemination, and the pregnancy rate at 120 d postpartum was 13.0 percentage units higher than before herd visits. Consequently, reproductive performance of those herds during visits was similar to that of contemporaries under a herd health program.

Animal Husbandry↗
PubMed2006

Synchronization of estrus and ovulation in sows not conceiving in a scheduled fixed-time insemination program.

A field study was conducted to investigate the effectiveness of a treatment with altrenogest, eCG and hCG or the GnRH-analogue D-Phe(6)-LHRH to synchronize estrus and ovulation of sows diagnosed as non-pregnant in order to reintegrate them back into a scheduled fixed-time insemination program. Sows (n=531) diagnosed as non-pregnant by ultrasonography on days 21-35 after insemination were subjected to one of three treatments: (1) 16 mg altrenogest/day/animal orally for 15 days to block follicular growth, followed by injection of 1000 IU eCG intramuscularly (i.m.) 24h after withdrawal of altrenogest to stimulate follicular growth and 500 IU hCG i.m. 78-80 h after eCG to induce ovulation; (2) similar to (1) except that 20mg altrenogest and 800 IU eCG were used and (3) similar to (2) except that 50 microg D-Phe(6)-LHRH was used to induce ovulation. Females were artificially inseminated (AI) twice at 24 and 40 h, respectively, after hCG/D-Phe(6)-LHRH. Success of treatments was checked by ultrasonography of the ovaries. Rates of conception and farrowing (CR, FR), and number of total and live born piglets (TB, LB) were recorded and compared to those of synchronized first served sows. Females had differing ovarian structures prior to treatment. Altrenogest effectively blocked follicular growth in >80% of the females irrespective of dosage, but 16 mg increased the development of polycystic ovarian degeneration. Four to 18% of the females still had corpora lutea after altrenogest. Most females ovulated either between both inseminations or thereafter (P<0.05). Females treated with D-Phe(6)-LHRH tended to ovulate earlier than those injected with hCG. The CR and FR were up to 25% lower for sows diagnosed as non-pregnant than for sows after first service (P<0.05). Among sows diagnosed as non-pregnant the CR was higher in females treated with D-Phe(6)-LHRH (P<0.05). No differences were found in regard to numbers of TB and LB. In conclusion, a treatment with 20mg altrenogest per day per animal, followed by 800 IU eCG and 50 microg the GnRH-analogue D-Phe(6)-LHRH is appropriate to synchronize estrus and ovulation of sows diagnosed as non-pregnant. Whether there might be a need to feed altrenogest for a longer interval of 18 days has to be investigated.

Animals↗