Our group has previously shown that maternal size can affect embryonic development by Day 19 of gestation and lamb birth weight. This study set out to investigate the effect of the maternal uterine environment on fetal growth at mid-gestation. Pure-breed single embryos were transferred within and reciprocally between large (Suffolk: S) and small (Cheviot: C) breeds of ewes to establish four maternal environments; SinS, SinC, CinS and CinC. On Day 90 of gestation, 37 single-bearing recipient ewes (10 CinC, 7 SinC, 10 CinS and 10 SinS) were euthanased. Fetal body weight, fetal body dimensions and fetal organ weights, and placentome number and total weight were measured. Body weight was significantly (P < 0.001) smaller in Cheviot compared to Suffolk fetuses. However, Cheviot fetuses had heavier (P < 0.05) kidneys and liver than Suffolk fetuses. SinC fetuses had heavier (P < 0.05) pancreas than those from all other pregnancy groups. CinS fetuses tended to have longer (P < 0.10) fore- and hind-leg lengths than CinC fetuses. There were no differences (P > 0.05) in placental parameters between the pregnancy groups. The maternal uterine environment had no major effect on fetal weight, fetal dimensions and fetal organ mass at mid-gestation.
Proceedings of the New Zealand Society of Animal Production, Volume 72, Christchurch, 205-209, 2012
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