Published online by Cambridge University Press: 02 September 2010
The intakes of concentrates and hay by individuals in three groups of ewes were estimated at three-weekly intervals in late pregnancy from faecal output; chromic oxide was incorporated as a marker in the concentrates. The groups were: (1) 16 mature ewes, (2) 16 2-year-old ewes, (3) eight mature and eight 2-year-old ewes. A constant daily hay allowance of 734 g dry matter (DM)/sheep was given but the concentrate was increased from an equivalent of 96 g DM/sheep at the beginning of the experiment to 435 g at the end. Individual concentrate intakes were most variable when the group allowance was small (CV over 50% in the mixed group) but variation decreased when amounts of concentrates were increased to contribute up to 47% of the total digestible DM intake. The CV for the total digestible DM intake ranged from 13 to 24%.
The younger sheep were at no disadvantage when penned with mature ewes. Intakes by individual ewes were compared with their calculated requirements and several twin-bearing ewes were shown to have a substantial energy deficit which was confirmed by their higher plasma ketone concentrations.
A major practical difficulty in group-feeding pregnant ewes is to ensure that the ewes with the highest foetal burden are adequately fed.