Effects of lactation length and an exogenous progesterone and estradiol-17β regimen during embryo attachment on endogenous steroid concentrations and embryo survival in sows

• Published in: Theriogenology 2002-05, Vol.57 (8), p.2063-2081
• Main Authors: Belstra, B.A., Diekman, M.A., Richert, B.T., Singleton, W.L.
• Format: Article
• Language: English
• Subjects: Early weaning; Embryo mortality; Lactation length; Progesterone; Sow
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/S0093-691X(02)00675-1

The hypotheses that short lactation lengths increase embryo mortality by altering endogenous post-weaning steroid concentrations, and that an exogenous steroid regimen during embryo attachment might increase embryo survival were tested using 36 s parity sows assigned randomly to a 2×2 factorial. Sows were subjected to either a short lactation (SL, 13.0 days, n=25) or a long lactation (LL, 31.5 days, n=11), artificially inseminated at first estrus and treated daily with 2 ml i.m. of either 25 mg progesterone (P 4) and 1.25 μg estradiol-17β (E 2) (steroid treatment, ST, n=17) or the vehicle alone (control treatment, CT, n=17) on Days 14–20 post-insemination. Blood samples were collected by jugular venipuncture from weaning to 24 days post-insemination on alternate days. Sows subjected to the SL compared to the LL tended to have a longer weaning-to-estrus interval (WEI) (5.3 versus 4.6 days; P0.10). The SL and LL sows had a similar ovulation rate (19.9 versus 21.3 corpora lutea, CL; P>0.05), but SL sows had fewer viable embryos than LL sows (11.5 versus 15.3; P