Prolonging the MGA-prostaglandin F2α interval from 17 to 19 days in an estrus synchronization system for heifers

Lamb, G.C.; Nix, D.W.; Stevenson, Jeffrey S.; Corah, L.R.

doi:10.1016/s0093-691x(99)00267-8

Cited by 46 publications

(19 citation statements)

References 20 publications

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“…In cattle, several protocols are effective at controlling the estrous cycle and reducing the time required to detect estrus (1)(2)(3), but the timing of ovulation is imprecise, which makes it difficult to inseminate cows at a fixed time. When fixed-time insemination protocols (protocols that synchronize ovulation) are attempted, gonadotropin-releasing hormone (GnRH) is used to induce ovulation.…”

mentioning

confidence: 99%

Relationship between follicle size at insemination and pregnancy success

Perry

Smith

Lucy

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

396

309

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Administration of gonadotropin-releasing hormone (GnRH) induces a surge of luteinizing hormone and ovulation in a variety of species, including human beings. Our objectives were to determine the effect of follicle size at the time of ovulation on corpus luteum function and establishment and maintenance of pregnancy in cows in which ovulation was either spontaneous or induced with GnRH. GnRH-induced ovulation of follicles Շ11 mm in diameter resulted in decreased pregnancy rates and increased late embryonic mortality. This decrease in fertility was associated with lower circulating concentrations of estradiol on the day of insemination, a decreased rate of increase in progesterone after insemination, and, ultimately, decreased circulating concentrations of progesterone. In contrast, ovulatory follicle size had no apparent effect on fertility when ovulation occurred spontaneously. Follicles undergoing spontaneous ovulation do so at a wide range of sizes when they are physiologically mature. Therefore, administration of GnRH to induce ovulation likely initiates a preovulatory gonadotropin surge before some dominant follicles attain physiological maturity. GnRH-induced ovulation of follicles that are physiologically immature has a negative impact on pregnancy rates and late embryonic͞fetal survival. These observations in cattle may have implications for assisted reproductive procedures in human beings.ovulation ͉ cattle ͉ artificial insemination ͉ embryonic mortality ͉ fertility P rocedures that control the timing of ovulation in human beings and other mammals are of enormous value in advancing the use of assisted reproductive technologies. In cattle, several protocols are effective at controlling the estrous cycle and reducing the time required to detect estrus (1-3), but the timing of ovulation is imprecise, which makes it difficult to inseminate cows at a fixed time. When fixed-time insemination protocols (protocols that synchronize ovulation) are attempted, gonadotropin-releasing hormone (GnRH) is used to induce ovulation. In some synchronization protocols, GnRH is administered 9 days before insemination to induce ovulation and corpus luteum (CL) formation and to initiate a new follicular wave. Two days before insemination, prostaglandin F 2␣ is administered to induce luteolysis, and 48 h later, GnRH is administered to induce ovulation of the preovulatory follicle (4, 5). Insemination is performed at the time of the second GnRH injection (4) or 16-24 h after the second GnRH injection (5).Bovine follicles achieve ovulatory capacity at Ϸ10 mm in diameter. However, a larger dose of luteinizing hormone is required to induce ovulation of a 10-mm follicle than to induce ovulation of larger follicles (6). In cattle, the efficiency of a single injection of GnRH to induce ovulation and thereby synchronize the initiation of the subsequent follicular wave is only 66% when evaluated across all stages of the estrous cycle (7). Because of this variation in ovulatory response, we hypothesized that considerable variation would e...

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mentioning

confidence: 99%

Relationship between follicle size at insemination and pregnancy success

Perry

Smith

Lucy

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

396

309

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“…More recently we observed a significant improvement in synchrony of estrus without compromising fertility in postpartum beef cows and beef heifers that were pretreated, either short or long term, with MGA before GnRH and PGF 2α administration. 4,5 CR in cows decreased from approximately 70% 6,7 to 35%, 8,9 although CR in heifers remained steady at approximately 70%. The cumulative data suggest that new methods of inducing and synchronizing estrus for postpartum beef cows and replacement beef heifers in which a progestogen is included in the GnRH-PGF 2α protocol offer significantly greater potential to more effectively synchronize estrus, with resulting high fertility.…”

Section: Discussionmentioning

confidence: 91%

Progestogen-Based Estrus Synchronization for Beef Replacement Heifers and Cows

Patterson¹,

Smith²

2007

Current Therapy in Large Animal Theriogenology

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“…This treatment places all animals in the late luteal stage of the estrous cycle at the time of PG injection, the synchronized period and conception rate. Although a 19-day interval is optimal, 17-to 19day intervals produce acceptable results and provide flexibility for extenuating circumstances (Brown et al, 1988;Deutscher, 2000 andLamb et al, 2000).…”

Section: Resultsmentioning

confidence: 99%

“…The MGA/prostaglandin (PGF) method of estrous synchronization has proven to be very successful in synchronizing estrus in beef heifers (Patterson and Corah, 1992). One disadvantage to the MGA/PGF protocol is that MGA must be fed for 14 day followed 17-19 day later withy an injiection of PGF (Lamb et al, 2000). However, when MGA is fed in the absence of a functional corpus luteum (CL), a dominant follicle persists and fertility at the ensuing estrus is reduced (Custer et al, 1994 andPatterson et al, 1989).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Estrus and Pregnancy Rates in Friesian Lactating Cows Synchronized With Melengesterol Acetate-Based Protocols

Hamd¹,

Metwally

Ghallab

et al. 2014

Journal of Animal and Poultry Production

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The objective of this study was to evaluate estrus synchronization and pregnancy rate of Friesian lactating cows during postpartum period in melengesterol acetate (MGA) based protocols for estrus synchronization. The total 30 dairy cows were used in this study, average age between 25-68 months and weighting 440 -620 kg and 1-5 parities was used in this study. At the beginning of the experimental period, the experimental cows were divided }}}into three similar groups, 10 in each. Cows in the 1 st treatment were fed on 0.5 g MGA/cow/day for 14 days. In the 2 nd treatment, cows were fed on 0.5 g MGA/cow/day for 14 days followed 33 days later by injection with 3 ml PGF2α. In the 3 rd treatment, cows were fed 0.5 g MGA/cow/day for to 14 days followed 26 intramuscularly injected with the 1 st dose of 5 ml GnRH, followed 33 days injected with 3 ml PGF2α followed 36 days injected with the 2 nd dose GnRH and fixed-time insemination. Results revealed that estrus response after the end of hormonal protocols were statistically (P<0.05) significantly higher in MGA and MGA+PGF2α protocols (90%) than the MGA select protocol (70%). Pregnancy rates assessed in all cows after AI tended to be higher (90%) for the MGA+PGF2α protocol and moderate in MGA select protocol (80%) than in the MGA protocol being for lower (70%). Progesterone concentration (P4) was above 1 ng/ml in all treated animals pretreatment ranging 2.308 -3.073 ng/ml. After the oral feeding MGA 0.5 g/cow/day, P4 concentration at days of 7 and 14 was increased in all animals of different protocols than in all animals in pre-treatments. On day 24 post-service, concentration of P4 was higher in responded animals, indicating incidence of pregnancy which were conceived after the PGF2α injection in MGA+PGF2α protocol and GnRH injection of MGA select protocol. The economic evaluation indicated that MGA protocol had the cheapest cost (L.E 4.9/cow), followed by MGA+PGF2α protocol (L.E 16.9/cow). While, MGA select protocol showed the highest cost (L.E 56.9/cow).In conclusions cows treated by MGA+PGF2α protocol at insemination based on heat incidence to improve their reproductive performance. From the economic point of view, MGA+PGF2α protocol showed the best results (conception rate and costs) compared to the other protocols.

show abstract

Prolonging the MGA-prostaglandin F2α interval from 17 to 19 days in an estrus synchronization system for heifers

Cited by 46 publications

References 20 publications

Relationship between follicle size at insemination and pregnancy success

Relationship between follicle size at insemination and pregnancy success

Progestogen-Based Estrus Synchronization for Beef Replacement Heifers and Cows

Evaluation of Estrus and Pregnancy Rates in Friesian Lactating Cows Synchronized With Melengesterol Acetate-Based Protocols

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