Productivity of lactating Merino and crossbred ewes given oats supplemented with urea or lucerne chaff

Abstract

Lactating Merino ewes with single lambs were offered iso-nitrogenous diets of oats + 1 5% urea, or oats + 30% lucerne chaff (W/W air dry) at intakes ranging from 12 to 20 g digestible dry matter/kg liveweight. day (g DDM/kg. d). Crossbred ewes with twin lambs were given similar rations at two levels of intake (two or three x maintenance). Multiple regression equations indicated that the Merino ewes given oats + lucerne chaff at 14 g DDM/kg. d maintained the growth of their lambs at the same rate (171 g/d) as ewes given oats + urea at 18 g DDM/kg.d (1 69 g/d). Similarly, crossbred ewes given 1.0 kg DDM/d of oats +lucerne chaff maintained the growth rate of their lambs at only 17 g/d less (P>0. 05) than lambs raised by ewes given 1 .4 kg DDM/d of oats + urea. These differences were associated with the Merino and crossbred ewes given oats + lucerne chaff losing more liveweight than ewes given oats + urea at the same level of digestible dry matter intake/d.