Changes in the maternal body and feto-placental growth following various lengths of feed restriction during mid-pregnancy in sheep

Abstract

The impact of maternal feed restriction during pregnancy on components of the maternal body and feto-placental growth was investigated to assess its influence on lamb birth weight. Single-bearing ewes were well-fed for the duration of pregnancy or feed restricted between the 30th and 96th, 50th and 96th or 75th and 96th day of pregnancy. Well-fed ewes increased in liveweight between the 30th and 96th day of pregnancy (48 g/day), while ewes feed restricted between the 30th and 96th, 50th and 96th and 75th and 96th day of pregnancy lost 55, 87 and 203 g/day respectively. Maternal fat deposits and muscle tissue of feed restricted ewes at the 96th day of pregnancy were less than for well-fed ewes. Placental weight was lower (P < 0.05) in ewes feed restricted between the 30th and 96th day of pregnancy, but not in ewes feed restricted between the 50th and 96th or the 75th and 96th day of pregnancy. Re-feeding ewes at the 96th day of pregnancy following feed restriction between the 30th and 96th day of pregnancy was associated with muscle tissue deposition during late pregnancy, while well-fed ewes depleted both fat deposits and muscle tissue during lat pregnancy. Lamb birthweight was not significantly affected by feed restriction during mid-pregnancy, despite various rates of depletion and repletion of maternal body reserves, and different patterns of placental growth.