Maternal Recognition of Pregnancy in Swine. I. Minimal Requirement for Exogenous Estradiol-17β to Induce Either Short or Long Pseudopregnancy in Cycling Gilts1

Abstract

Five experiments were conducted to determine the minimal requirement for estradiol-17 beta (E2) injections to induce either short pseudopregnancy (SPP) or long pseudopregnancy (LPP) in cycling gilts. In experiments 1 through 5, E2 was injected i.m. on combinations of days between 11 and 25 days postestrus. Exogenous E2 on Days 12 and 13 or on Days 12 through 19 was optimal for induction of SPP or LPP, respectively. The duration of E2-induced diestrus was clearly demarcated between SPP (n = 73, duration 23-35 days) and LPP (n = 23, duration > 50 days). A sixth experiment was conducted to determine the minimum dose of intrauterine E2 required to induce SPP, and these gilts received intrauterine infusions of 0, 4, 40, or 400 micrograms E2 per 24 h on Days 12 and 13 postestrus. Pseudopregnancy was induced in 0 of 12, 1 of 4, 1 of 11, and 4 of 7 gilts in the treatment groups, respectively. These data suggest that uterine exposure alone is not sufficient to induce SPP. The present results indicate that the optimal signal for inducing LPP in unmated cycling gilts, and perhaps also for maternal recognition of pregnancy in mated gilts, may occur in two phases with continuous exposure to E2 being required from Day 12 to Days 17-19.

Prostaglandin F2α promotes angiogenesis and embryo–maternal interactions during implantation

“…In studies on the mechanisms of maternal recognition of pregnancy in pigs, usually in vivo models of pseudopregnancy are used in which 5 mg of E 2 benzoate is administered systemically on days 11-15 of the estrous cycle, resulting in pharmacological concentrations of E 2 (Frank et al 1977, Geisert et al 1982, Pusateri et al 1996, Kawarasaki et al 2012. The novel approach applied in our study allowed us to examine both local and systemic effects of E 2 in concentrations close to the physiological levels secreted by embryos into the uterine lumen.…”

Embryo Transfer andin vitroFertilization

“…Synchronization schemes in some of the other species covered in this review are more complicated than in cattle and horses. For example, progesterone and estrogen treatments do not work in pigs as they do in cattle because estrogen may induce pseudopregnancy (Pusateri et al, 1996). This is because estrogen is the signal for maternal recognition of pregnancy in the pig (Bazar et al, 1986).…”

Maternal Recognition of Pregnancy in Swine. II. Plasma Concentrations of Progesterone and 13,14-Dihydro-15-Keto-Prostaglandin F2α, during the Estrous Cycle and during Short and Long Pseudopregnancy in Gilts1

“…Extensions in luteal function lasting approximately 1 wk have been observed after administration of prostaglandin E 2 [7,8]. In contrast, exogenous estrogen may yield either short (1-2-wk) or long (over 50-day) periods of extended luteal function, depending on the duration of estrogen exposure [9,10].…”

“…The properly timed administration of estrogens to unmated gilts or sows induces a state of luteal persistence resulting in increased interestrous intervals [11] and a state sometimes called pseudopregnancy [10,12]. It appears that there are two distinct types of pseudopregnancy-short pseudopregnancy (SPP) and long pseudopregnancy (LPP)-and that these two types can be selectively induced by different regimens of estrogen administration [9,10].…”

“…It appears that there are two distinct types of pseudopregnancy-short pseudopregnancy (SPP) and long pseudopregnancy (LPP)-and that these two types can be selectively induced by different regimens of estrogen administration [9,10]. The SPP involves an extension of the interestrous interval to approximately 26 or 27 days, whereas LPP is characterized by an interestrous interval of over 50 days.…”