EFFECT OF SUPPLEMENTARY FEEDING AND HERBAGE MASS ON THE INTAKE AND PERFORMANCE OF GRAZING EWES IN EARLY LACTATION

Two experiments were conducted to examine the effects of a cereal-based supplement and herbage mass on the intake and performance by Border Leicester .times. Scottish Blackface ewes nursing twin lambs in early lactation. In 1 experiment 16 ewes, individually penned, were given 1 of 4 amounts of supplement (0, 320, 640 and 960 g organic matter/ewe per day) and offered ad lib freshly-cut perennial ryegrass herbage (organic-matter digestibility 82%). Intake of herbage and total organic matter digestibility declined linearly with increasing intake of supplement (0.84 g organic matter of herbage/g organic matter of supplement and 0.50 percentage units/100 g organic matter of supplement, respectively). In the 2nd experiment 3 amounts of supplement (0, 480 and 960 g organic matter/ewe per day) were offered individually to groups of 7 ewes grazing a perennial ryegrass sward of high digestibility, maintained at herbage masses of either 500 or 750 kg organic matter/ha. Another group of 7 unsupplemented ewes were grazed on the same sward maintained at 1500 kg organic matter/ha. Intakes of herbage and digestible organic matter by ewes, and lamb live-weight gain, were all significantly greater and ewe live-weight loss significantly less at herbage masses of 750 and 1500 than at 500 kg organic matter/ha (P < 0.05). The mean decline in herbage intake was 0.93 g organic matter/g organic matter supplement consumed. Amount of supplement had no significant effect on lamb live-weight gain at either weight of herbage nor on ewe live-weight loss at the 750 kg organic matter/ha herbage mass. At 500 kg organic matter/ha herbage mass, intake of digestible organic matter was significantly greater and ewe live-weight loss was significantly less for 960 than for 0 and 480 g organic matter/day amounts of supplement (P < 0.05).