Influence or maize supplementation and stocking rate on production or ewes and lambs on winter sourveld: Body mass changes of lactating ewes and lambs with different types of maize supplements on winter sourveld were investigated over three consecutive seasons in a 3 X 2 X 2 factorial experimental design. Camps were grazed for 60 days in June to August at either 3 or 6 kg available DM/ewe/d. Maize grain at 300 g and cob and corn at 350 g/ ewe/d were supplied to ewes. A protein energy lick was also supplied to ewes whilst creep feed was available to lambs. The effect of manipulating rumen fermentation by means of these energy supplements was also investigated in a digestion trial with 12 rumen-fistulated wethers. Rumen pH, intake and digestibility were the main parameters investigated. Caustic soda treatment of the energy supplements increased the rumen pH from 6,1 to 6,3 (P ≤0,01). Supplementation with cob and com (6,3) and maize grain (6,2) also resulted in a higher (P ≤0,01) rumen pH compared with no maize supplementation (6,1). Significant differences in grass intake (764 ± 17 g), DM digestibility (58,7 ± 0,8%) and fibre digestibility (61,1 ± 1%) were not recorded. Caustic soda treatment of the energy supplements resulted in a 15% (P ≤0,01) decrease in creep feed intake by lambs. Lambs maintained a higher ADG (P ≤0,01) when ewes received energy supplementation (161 and 153 vs. 136 g). The loss in body mass by ewes tended to be lower (77 vs. 87 g/d) at the higher herbage availability (6 kg DM). Caustic soda treatment of energy supplements resulted in a 15% (P ≤0,01) reduction in lick intake (162 vs. 191 g/ewe/d) without affecting the loss in body mass (82 ± 4,3 g/ewe/d).