EFFECT OF LAMBING DATE ON PRODUCTTON FROM BREEDING EWES AND ON PASTURE ALLOWANCE AND INTAKE

Abstract

In an attempt to improve the synchronization of the feed requirements of the breeding ewe with the onset of spring pasture growth, lambing was delayed one month (mean lambing date August 31 vs. October 1) in a 3-year experiment with 5-year-old ewes stocked at two rates (21.3 vs. 27.7 ewes/ha). There was no effect of stocking rate or lambing date on annual pasture growth. However, the later lambing groups had higher available pre-grazing DM yields in late pregnancy and early lactation. This resulted in higher pasture allowances and pasture intakes in late pregnancy (+ 0.6 and + 0.3-0.5 kg DM/ewe/day) and in early lactation (+ 1.4 and + 0.3-0.9 kg DM/ewe/day), respectively. The late lambing ewes were 5 kg and 1.5-2.0 kg heavier pre-lambing and 4 weeks postlambing, while their lambs were 0.7-1.4 kg heavier at 4 weeks. Compared with the early groups the later lambing ewes lost more weight and their lambs had lower growth rates from weeks 4 to 10 of lactation, although pasture allowances and intakes were similar to the early groups during the same lactation period. The poorer performance of the later lambing groups over this period appeared to be associated with a decline in pasture digestibility.