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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2007-0440v1 86/8/1996    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Patterson, J. Articles by Foxcroft, G. PubMed PubMed Citation Articles by Patterson, J. Articles by Foxcroft, G.

Responses to delayed estrus after weaning in sows using oral progestagen treatment¹

J. Patterson^*,2, A. Wellen^*, M. Hahn^*, A. Pasternak^*, J. Lowe, S. DeHaas, D. Kraus, N. Williams and G. Foxcroft^*

^* Swine Reproduction-Development Program, Dept. AFNS, University of Alberta, Edmonton, Alberta, T6G 2P5, Canada; and The Maschhoffs Inc., 7475 State Road 127, Carlyle, IL 62231; and and PIC North America, 100 Bluegrass Commons Boulevard, Suite 2200, Hendersonville, TN 37075

² Corresponding author: jlp2{at}ualberta.ca

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 (M0; 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 (M0) or altrenogest withdrawal, and every 24 h thereafter, until they no longer exhibited the standing reflex. The WEI for M0 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 M0 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 M0 (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 M0 (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 M0 (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.

Key Words: estrus • lactation • postweaning fertility • progestagen • sow