Effect of nutrition around the time of breeding and during pregnancy on yearling liveweight change, pregnancy loss and live weight and survival of their offspring

This experiment investigated the effects of differing nutritional levels on yearling pregnancy loss, and the live weight and survival of their offspring to weaning. Yearlings were offered either Medium or Ad-libitum levels of herbage from four days prior to breeding (P-4) until P145. Nutrition during pregnancy had no effect on pregnancy loss or lamb live weight from Day 0 of lactation (L0) until L55. Lambing percent was higher (P <0.05) in the Ad-libitum treatment compared to the Medium treatment. Single born lambs were heavier (P <0.05) than twin born lambs at L0 and at L55. Ad-libitum treatment yearlings were heavier (P <0.05) than Medium treatment yearlings at L55. Modelling of the live weight trends indicated that from P-4 until P145 the pregnant yearlings in the Medium and Ad-libitum treatment groups consumed 8.1 and 14.4 kg DM/kg of lamb live weight at L55. This indicates that the greater yearling live weight gain in the Ad-libitum group utilised more herbage during the yearling’s first winter without any increase in the performance of their offspring. The extra 9 kg gained by the yearlings fed Ad-libitum may have positive effects on future performance as they will gain a suitable live weight for breeding as a two year old earlier.