Evidence for a two-phase signal for the maternal recognition of pregnancy in swine
Abstract
Experiments were conducted to examine events associated with luteal maintenance after estradiol-17$\beta$ (E2) administration. An interestrous interval greater than 23 days, with an extension of at least 3 days over pretreatment was termed short pseudopregnancy (SPP). Long pseudopregnancy (LPP) required an interestrous interval of at least 50 days. In Exp 1, gilts were injected im with E2 at 4, 8, or 17 mcg/kg BW and serum E2 concentrations were determined. In Exp 2-5, gilts were injected with E2 on combinations of days between days 11 and 25 post-estrus to determine the timing required to induce SPP and LPP. In Exp 6, gilts received intra-uterine infusions of 1, 10, or 100 mcg E2 every 6 hours on days 12 and 13 post-estrus to determine the dose required to induce SPP. Exp 7 was conducted to determine plasma progesterone (P4) and 13,14-dihydro-15-keto-prostaglandin F$\sb2$-alpha (PGFM) concentrations during SPP and LPP. In Exp 1, E2 concentrations were elevated for 18 hours post-injection. In Exp 2-5, SPP was consistently induced by injection of E2 on days 12 and 13. LPP was induced by injection of E2 on days 12-19; injections on days 12-16 resulted in no LPP gilts. In Exp 6, 1 of 4, 1 of 11, and 4 of 7 gilts on the 1, 10, and 100 mcg E2 treatments were SPP, respectively. In Exp 7, plasma PGFM concentrations peaked and P4 concentrations declined rapidly 4 to 6 days before estrus in nonpseudopregnant, SPP, and LPP gilts. LPP gilts exhibited interestrous intervals greater than 110 days. Overall, there was a clear demarcation between SPP and LPP. Of 119 pseudopregnant gilts, 90 had interestrous intervals between 23 and 35 days (mean +/$-$ SEM; 27.1 +/$-$.3 days) and 28 had intervals greater than 50 days. Interesterous interval in controls was 19.6 +/$-$.2 days. Results suggest that maternal recognition of pregnancy in swine may involve an initial phase of estrogen exposure on days 12 and 13 followed by a second phase of continued estrogen exposure through day 19. SPP and LPP appear to result from a delay in uterine prostaglandin F$\sb2$-alpha release.
Degree
Ph.D.
Advisors
Diekman, Purdue University.
Subject Area
Anatomy & physiology|Animals
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