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This Article Full Text Full Text (PDF) All Versions of this Article: 70/1/92    most recent biolreprod.103.020214v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal My Folders Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Vallet, J.L. Articles by Christenson, R.K. Search for Related Content PubMed PubMed Citation Articles by Vallet, J.L. Articles by Christenson, R.K. Agricola Articles by Vallet, J.L. Articles by Christenson, R.K.

Effect of Progesterone, Mifepristone, and Estrogen Treatment During Early Pregnancy on Conceptus Development and Uterine Capacity in Swine¹

USDA, ARS, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska 68933

A series of experiments was performed to investigate the influence of progesterone at Days 2 and 3 of pregnancy on conceptus development and uterine capacity. In experiment 1, unilaterally hysterectomized-ovariectomized (UHO) white crossbred gilts were given no treatment, estradiol valerate (5 mg given on Days 11 and 12), or progesterone (200 mg/day on Days 2 and 3 after mating). On Day 105 of pregnancy, each fetus and its associated placenta were weighed, and the number of live and dead fetuses was recorded for each litter. Early progesterone treatment reduced (P < 0.05) litter size (a measure of uterine capacity in UHO gilts). In experiment 2, intact white crossbred gilts were mated, given no treatment or progesterone treatment on Days 2 and 3 of pregnancy, and farrowed. Progesterone treatment decreased (P < 0.05) pregnancy rates. In pregnant gilts, progesterone had no effect on the number of live or stillborn piglets at birth, and gestation length was decreased (P < 0.05). Progesterone treatment did not affect the number of large or small piglets. In experiment 3, intact gilts were mated at estrus and then received 1) no treatment or treatment with 2) 100 mg, 3) 200 mg, or 4) 400 mg mifepristone (also known as RU486) on Day 2 of pregnancy. On Day 11 of pregnancy, both uterine horns were flushed, the number and diameter of each conceptus was recorded, and the flushed material was assayed for total protein and acid phosphatase. The 400 mg mifepristone treatment decreased conceptus diameter (P < 0.05) and total protein (P = 0.06) in the uterine flushings. In experiment 4, UHO gilts were mated at estrus, injected with either corn oil (control) or mifepristone (400 mg) on Day 2 of pregnancy, and killed on Day 105 of pregnancy, and the number and weight of live fetuses and placentas was recorded. In contrast to the effect of progesterone treatment, mifepristone decreased uterine capacity by decreasing the number of small conceptuses. These data suggest that progesterone concentrations on Days 2 and 3 of pregnancy in swine influence the rate of conceptus development during early pregnancy and uterine capacity during later pregnancy.

¹ Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendations or endorsement by the U.S. Department of Agriculture.

² Correspondence: J.L. Vallet, USDA, ARS, Roman L. Hruska U.S. Meat Animal Research Center, P.O. Box 166, State Spur 18D, Clay Center, NE 68933. FAX: 402 762 4382; vallet{at}email.marc.usda.gov

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