Estrus Synchronization with Pseudopregnant Gilts Induced by a Single Treatment of Estradiol Dipropionate

Abstract

Abstract. The aims of this study were to determine whether a single treatment of estradiol dipropionate (EDP) could induce pseudopregnancy in gilts and to determine the effectiveness of PGF2α treatment on estrus synchronization in EDP-induced pseudopregnant gilts. In experiment 1, gilts were treated with 20 mg of EDP (n=11) or vehicle (n=5) on Day 12 (Day 0=onset of estrus). Establishment of pseudopregnancy was defined as a lack of estrus and maintenance of the plasma progesterone concentration above 1 ng/ml between Days 12 and 36. Nine of 11 gilts (82%) treated with EDP became pseudopregnant. The plasma estradiol-17β level was significantly higher in the EDP-treated gilts than in the control gilts until Day 29. In experiment 2, PGF2α was administered twice with a 24-h interval from Day 36 in pseudopregnant gilts (n=6) or Day 10 in cyclic gilts (control; n=5). Estrus after PGF2α treatment was observed in 83% of the pseudopregnant gilts. The interval from the day of the first PGF2α treatment to the onset of estrus and the peak of the LH surge was significantly shorter in the pseudopregnant gilts than in the control gilts. In experiment 3, six pseudopregnant gilts were bred by artificial insemination at the estrus after PGF2α treatment. The farrowing rate and average litter size did not differ between the PGF2α-treated pseudopregnant and cyclic gilts. These results indicate that a single treatment of EDP on Day 12 of the estrous cycle can induce pseudopregnancy in pigs and that a convenient protocol for administering PGF2α to EDP-induced pseudopregnant pigs is available for estrus synchronization programs in cyclic pigs. Key words: Estradiol dipropionate, Estrus control, Pig, Pseudopregnancy (J. Reprod. Dev. 56: [421][422][423][424][425][426][427] 2010) t is desirable to have female pigs in estrus at certain times to provide maximum use of intensive pork production facilities. Application of estrus synchronization programs enhances economic performance in the swine industry by reducing the labor required to detect estrus, facilitating the use of artificial insemination (AI) and assisting in batch farrowing. Therefore, being able to control the time of estrus in a breeding herd results in decreased reproductive efforts and costs.Artificially shortening or extending the luteal phase is important for control of the interestrous interval in cyclic animals. The corpus luteum (CL) of the cycling pig generally exhibits resistance to prostaglandin F2α (PGF2α)-induced luteolysis prior to Day 12 of the estrous cycle [1][2][3]. Consequently, multiple administrations of PGF2α in the early luteal phase are required to induce luteolysis of the functional CL and shorten the estrous cycle [2,3]. In contrast to the CL before Day 12 of the estrous cycle, the CL of the pregnant pig easily reacts to exogenous administration of PGF2α [4,5], and prompt estrus can be induced between 4 and 7 days after PGF2α treatment; however, exogenous administration of PGF2α is associated with abortion in pregnant pigs [4,6].In pigs, two phases of ...

Reproductive Hormone Profiles in Sows on Estrus Synchronization using Estradiol Dipropionate and Prostaglandin F_2α-Analogue and the Reproductive Performance in Female Pigs on Commercial Farms

“…The decrease in progesterone levels to under 1 ng/ ml in pseudopregnant females induced by multiple injections of EB [5] and a single injection of EDP [17,18] occurred 21 − 57 hr and 24 − 48 hr after dinoprost treatment, respectively. In the present study, estrus was mainly observed 5 and 6 days after cloprostenol treatment similarly to dinoprost treatment in pseudopregnant females treated with EB [9,13] or EDP [17,18]. The present results and previous reports indicate that cloprostenol and dinoprost have equivalent effects on luteolysis and subsequent estrus exhibition in pseudopregnant females.…”

“…Animals were checked for estrus twice daily from 17 days after ovulation, and pseudopregnancy was defined as absence of estrus maintained until at least 20 days after EDP treatment, as described previously [17]. Pseudopregnant sows were treated with PGF 2α -A as 0.175 mg cloprostenol (Planate, Intervet, Osaka, Japan) intramuscularly twice over a 24-hr interval between 24 and 28 days after EDP treatment.…”

“…Animals were checked for estrus once or twice daily from 17 days after the end of estrus, and pseudopregnancy was defined as absence of estrus maintained until at least 20 days after EDP treatment, as described previously [17].…”

“…It has been reported that daily injection of estradiol benzoate (EB) from days 11 to 14 [9] of the estrous cycle or estradiol valerate (EV) from days 11 to 15 [27] can induce pseudopregnancy. We previously showed that a single administration of estradiol dipropionate (EDP), which exhibited prolonged estradiol-17β effects compared with EB and EV in rats [14] and humans [22], at 9 − 13 days after the onset of estrus could also induce pseudopregnancy in gilts and sows [17,18]. Administration of EDP appears to be more effective for inducing pseudopregnancy in females in terms of effort and cost compared with the previous method of using at least 4 administrations of EB or EV [7,9,27].…”

“…By contrast, the CL of pseudopregnant females induced by the above methods regresses rapidly after PGF 2α administration [5,17], and 83 − 92% of gilts [13,17,27] and 100% of sows [18] exhibit estrus 5 days after PGF 2α treatment, as well as pregnant females [5,21]. Thus, estrus synchronization protocol using pregnant or pseudopregnant female pigs can be applied for the introduction of females into planned piglet production by batch farrowing on commercial farms.…”