PHYSIOLOGICAL APPROACHES TO INCREASE THE EFFICIENCY OF PORK PRODUCTION THROUGH IMPROVED NUTRITIONAL AND REPRODUCTIVE COMPETENCE
Location: Reproduction Research
Title: Effect of Empty Uterine Space on Placental Development, Farrowing Intervals, and Stillbirth
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 31, 2009
Publication Date: June 20, 2009
Citation: Vallet, J.L., Miles, J.R., Brown Brandl, T.M., Nienaber, J.A. 2009. Effect of Empty Uterine Space on Placental Development, Farrowing Intervals, and Stillbirth [abstract]. Proceedings of VIIIth International Conference on Pig Reproduction, Banff, Alberta, Canada, p. 158.
Prolonged farrowing intervals (FI) are associated with stillbirth and decrease as litter size increases, but the reason is unclear. We hypothesized that unoccupied uterine space associated with small litters could present a barrier to delivery of piglets and increase FI. Empty uterine space was created in gilts by crushing 1 or 2 fetuses on either the ovarian (O) or cervical (C) end of uterine horns on day 35 of pregnancy. This also provided a test of the effects of adjacent empty uterine space on placental and fetal development. A subset (n = 27) of gilts were slaughtered at 105 days of gestation to determine whether the treatment was successful and to measure effects on the placenta and fetus. The rest of the gilts (n = 75) were farrowed and monitored with 24-h video. At slaughter, the lengths of empty regions of the uterus were measured. Each fetus was removed and weighed and the lengths of the ovarian- and cervical-facing halves of each placenta were measured from the umbilicus; then, each placenta was weighed. For farrowed gilts, each piglet’s status (live, stillborn, mummy) and FI were recorded. At slaughter, treatment successfully (P < 0.01) increased the length (cm) of empty uterine horn (O treatment, O end = 25.8 ± 2.1 vs. C end = 4.6 ± 2.0; C treatment, O end = 7.2 ± 2.8 vs. C end = 22.0 ± 2.7). This resulted in increased (P < 0.01) placental-half lengths (cm) adjacent to the empty spaces (O treatment, O half = 21.4 ± 1.2 vs. C half = 12.5 ± 1.2; C treatment, O half = 11.3 ± 1.2 vs. C half = 19.2 ± 1.2). Placental and fetal weights were greater (P </= 0.05) in empty space adjacent compared with nonadjacent fetuses. There were no effects of treatment on piglet FI or stillbirth. These data clearly indicate that (1) placental potential is not fixed by day 35 of gestation, (2) adjacent empty uterine space is advantageous to developing fetuses after day 35 of pregnancy, and (3) empty uterine space does not influence FI or stillbirth rates and therefore does not explain the effect of litter size on FI.