Effects on the rate of increase in fetal girth of refeeding ewes after short periods of severe undernutrition during late pregnancy.

A technique is described by which daily changes in the thoracic circumference (girth) of individual fetal sheep were observed during the last 60 to 70 days of pregnancy. The girth technique and a previously published method for measuring daily changes in the curved crown-rump length were both used to examine fetal growth responses when ewes were refed at 116 days of gestation after short periods of severe underfeeding. Refeeding ewes after nine or 16 days of severe underfeeding was associated in most cases with an immediate increase in fetal growth rate, whereas refeeding after 21 days had no effect on the rate in any fetus. Possible mechanisms underlying these effects are discussed. Using girth as an index the growth rates of individual lambs were measured before and after birth. There was a 3.3 fold increase in growth rate immediately after birth.