Partition of nutrients in moderately fat ewes compared with lean ewes given ad libitum access to feed in late pregnancy

Abstract

The effect of a difference in voluntary feed intake on fetal weight was tested in lean v. moderately fat ewes (0·15 v. 0·32 kg/kg fat-free empty body weight), by giving them ad libitum access to feed from Day 110 to 146 of pregnancy when both had placentas of a similar size (at Day 146: 437 v. 467 g, s.e.m. = 49·5, P > 0·05). Although the lean ewes ate 29% more than the fatter ewes above their estimated requirements (1258±106·9 v. 978±105·8 g/ewe · day, P = 0·08) fetal weights were not affected (4744 v. 4590 g, s.e.m. = 282·1, P > 0·05). Instead, the lean ewes partitioned more of their intake into body fat than the fatter ewes (0·13 v. 0·01 kg/kg fat-free empty body weight, P < 0·05). The results support the concept that the placenta places an upper limit to the uptake of nutrients by the fetus.