Assessment of contrasting perennial ryegrasses, with and without white clover, under continuous sheep stocking in the uplands

Abstract

AbstractPotential lamb production from grass‐clover (75–80 kg N ha−1) swards was compared with that from grass‐only (160–200 kg N ha−1) swards from 1985 to 1987 at the Bronydd Mawr Research Centre in mid‐Wales. Separate pastures of three perennial ryegrass (Lolium perenne L.) varieties; Aurora (very early‐flowering diploid), Meltra (late‐flowering tetraploid) and Aberystwyth S23 (late‐flowering diploid), with and without Aberystwyth S184 small‐leaved white clover (Trifolium repens L.), were continuously stocked with Beulah Speckled Face ewes and their Suffolk cross lambs from spring (late April) until weaning in mid‐July. From late July the pastures were grazed with weaned lambs until early November.Individual lamb liveweight gain was 8% more (P < 0·001) pre‐weaning on grass‐clover than on grass‐only swards and 30% more (p < 0·001) post‐weaning. Averaged over three years, mean stocking rate was 17% higher (p < 0·001) pre‐weaning and 29% higher (p < 0·001) post‐weaning on the grass‐only pastures. Even so, total lamb output (kg ha−1) was similar from the two sward types, although during the pre‐weaning period lamb production was 9% higher (P < 0·05) from grass‐only swards.The results show the potential of grass‐clover (low N) swards to improve the efficiency of lamb production from grassland since better individual lamb growth rate compensated for the lower stock‐carrying capacity. That is, similar output was achieved with lower cost of fertilizer N input and with the lower costs associated with carrying fewer animals.