Responses to delayed estrus after weaning in sows using oral progestagen treatment

J. Patterson, A. Wellen, M. Hahn, A. Pasternak, J. Lowe, S. Dehaas, D. Kraus, N. Williams, G. Foxcroft

Research output: Contribution to journalArticlepeer-review


Oral progestagen treatment extends the weaning-to-estrus interval (WEI) in weaned sows. Particularly in lower parity sows, this allows recovery from lactational catabolism and improves sow productivity. However, the optimal duration of progestagen treatment in contemporary dam-line sows is unclear. Therefore, sows (n = 749) weaned over consecutive 3-wk periods in June and July and classified as parity 2 and 3 (P2-3); 4, 5, and 6 (P4-6); or parity 7 or higher (P7+) were organized into 2 breeding groups using 1 of 3 strategies: 1) oral progestagen for 2 d before and 12 d after weaning (M14; n = 249); 2) oral progestagen for 2 d before and 5 d after weaning (M7; n = 250); or 3) no progestagen treatment (MO; n = 250). Progestagen (altrenogest) was administered directly into the sow's mouth at a dosage of 6.8 mL (15 mg of altrenogest) daily. Sows were bred using artificial insemination at first detection of estrus after weaning (MO) or altrenogest withdrawal, and every 24 h thereafter, until they no longer exhibited the standing reflex. The WEI for MO sows was 5.1 ± 0.1 d. Estrus was recorded sooner (P < 0.001) after withdrawing treatment in M14 than in M7 sows (6.9 ±0.1 vs. 7.4 ± 0.1 d, respectively). More (P < 0.001) M14 sows (88.6 ± 2.5%) were bred within 10 d of altrenogest withdrawal than M7 (72.8 ± 2.8%) sows, or within 10 d of weaning in MO sows (78.8 ± 2.6%). Reproductive tracts were recovered after slaughter at d 30 or 50 of gestation. For P2-3 sows, ovulation rate (least squares mean ± 95% confidence interval) in M7 (23.1 ± 1.0) was greater (P < 0.001) than in M14 (20.7 ± 1.0) or MO (19.7 ± 1.0) sows; no differences were detected in P4-6 and P7+ sows. At d 30, M7 and M14 sows had more (P < 0.01) embryos (16.4 ± 0.6 and 15.8 ± 0.4, respectively) than MO (13.9 ± 0.5) sows. At d 50 of gestation, number of fetuses in M14 sows (13.6 ± 0.4) was greater (P < 0.001) than in MO (11.8 ± 0.4) and M7 (12.2 ± 0.3) sows. Use of oral progestagen to delay the return to postweaning estrus for greater than 18 d appears to have potential for improving weaned sow productivity. Given the incidence of high ovulation rates and associated evidence of intrauterine crowding of embryos around d 30 of gestation, the changing dynamics of prenatal loss resulting from longer periods of progestagen treatment may represent an additional production advantage.

Original languageEnglish (US)
Pages (from-to)1996-2004
Number of pages9
JournalJournal of animal science
Issue number8
StatePublished - Aug 2008
Externally publishedYes


  • Estrus
  • Lactation
  • Postweaning fertility
  • Progestagen
  • Sow

ASJC Scopus subject areas

  • Food Science
  • Animal Science and Zoology
  • Genetics


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