title: Uterine crowding in the sow affects litter sex ratio, placental development and embryonic myogenin expression in early gestation.
abstract: Uterine crowding in the pig results in intrauterine growth restriction (IUGR), and permanently affects fetal muscle fibre development, representing production losses for the commercial pig herd. The present study sought to understand how different levels of uterine crowding in sows affects muscle fibre development in the early embryo at the time of muscle fibre differentiation and proliferation. Sows either underwent surgical, unilateral oviduct ligation (LIG; n = 10) to reduce the number of embryos in the uterus, or remained as intact, relatively-crowded controls (CTR; n = 10). Embryos and placentae were collected at Day 30 of gestation, and myogenic regulatory factor (MRF) transcript abundance was determined using real-time PCR for both myogenin (MYOG) and myoblast differentiation 1 (MYOD1). Unilateral tubal ligation resulted in lower numbers of embryos in utero, higher placental weights and a higher male : female sex ratio (P < 0.05). Relative MYOD1 expression was not different, but MYOG expression was higher (P < 0.05) in the LIG group embryos; predominantly due to effects on the male embryos. Relatively modest uterine crowding therefore affects MRF expression, even at very early stages of embryonic development, and could contribute to reported differences in fetal muscle fibre development, birthweight and thus post-natal growth performance in swine.
authors.affiliation: Swine Reproduction-Development Program, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada.
authors.forename: W-Y
authors.initials: WY
authors.lastname: Tse
authors.forename: S C
authors.initials: SC
authors.lastname: Town
authors.forename: G K
authors.initials: GK
authors.lastname: Murdoch
authors.forename: S
authors.initials: S
authors.lastname: Novak
authors.forename: M K
authors.initials: MK
authors.lastname: Dyck
authors.forename: C T
authors.initials: CT
authors.lastname: Putman
authors.forename: G R
authors.initials: GR
authors.lastname: Foxcroft
authors.forename: W T
authors.initials: WT
authors.lastname: Dixon
mesh_terms: D000818:Animals; D003441:Crowding; D004622:Embryo, Mammalian; D047108:Embryonic Development / Q000235:genetics; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005865:Gestational Age; D008098:Litter Size / Q000502:physiology; D008297:Male; D017570:MyoD Protein / Q000235:genetics; D018008:Myogenin / Q000235:genetics*; D010929:Placentation; D011247:Pregnancy; D012744:Sex Ratio; D013246:Sterilization, Tubal; D013552:Swine / Q000502:physiology; D014599:Uterus / Q000502:physiology*
chemical_list: D017570:MyoD Protein; C057363:MyoD1 myogenic differentiation protein; D018008:Myogenin