Effect of lactation length on ovulation rate and embryo survival in swine

Thomas A. Marsteller, DVM; Gregory A. Armbruster, DVM; David B. Anderson, PhD; Andy J. Wuethrich; Jody L. Taylor, MS; James T. Symanowski, PhD

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Objective: To evaluate the impact of early weaning on ovulation rate and embryo survival in sows.

Methods: A 900-sow commercial breeding herd was depopulated. Duringdepopulation, sows were either early weaned (EW; 8-12 day lactation length)or conventionally weaned (CW; 18-21 day lactation length). Data from 72early-weaned and 52 conventionally weaned sows were analyzed. Sows weremated during their first postweaning estrus. Sows were subsequently slaughteredat 33-51 days of pregnancy and reproductive tracts were collected. Ovarian,uterine, and embryo measurements were made.

Results: Ovulation rate in EW sows was not significantly different(20.3) from that of CW sows (20.7) (P =.646). Early-weaned sows hada significant decrease in embryo survival compared with CW sows (53% versus67%; P<.001), and thus had significantly fewer live embryos comparedwith CW sows (10.4 versus 13.0; P <.001). Live embryo weights(average individual embryo weight) in EW sows were also significantly decreasedcompared with CW sows (7.88 g versus 9.52 g; P =.006). Weaning-to-first-serviceinterval was significantly increased in the EW group (7.0 days versus 5.2days; P <.001). Conception rate was also significantly decreasedin EW sows (68%) compared with CW sows (87%) (P<.001).

Implications: In our study, embryo survival was a more importantfactor than ovulation rate in the decreased live embryo numbers found inpregnancies of EW sows (mean lactation length of 9.7 days). Further researchis needed to explore management opportunities that might improve embryonicsurvival in early-weaned sows and to investigate the apparently decreasedembryo weight in early-weaned sows.

Keywords: reproduction, early weaning, ovulation rate, embryo survival

RIS citationCite as: Marsteller T, Armbruster G, Anderson D, et al. Effect of lactation length on ovulation rate and embryo survival in swine. J Swine Health Prod 1997;5(2):49-57.

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