Some effects of botanical composition of pasture on growth and wool production of weaner sheep

Abstract

August-born Corriedale lambs were weaned at ten weeks old and, for the following 12 months, were grazed on 16 plots. Each plot had been sown six years previously, to one of eight pasture mixtures which differed in their grass component, but not in their clover component. Trifolium perenne, Phalaris tuberosa, Dacylis glomerata, Trifolium repens, T . subterraneum, and T. fragiferum were sown. Hordem leporinum volunteered in most plots. Where perennial grass species were sown, Trifolium repens (white clover) contributed less than two per cent to the pasture present on the plots. For the two plots where perennial grass was not sown, white clover contributed up to 31 per cent. The total for all sown clover species present in the pasture varied from approximately 100 to 1000 kg ha-1, or approximately 3-30 per cent. Apart from the two plots where perennial qrass was not sown, the clover species present was mainly Trifolium subterraneum (subterranean clover). Average fleece weights varied from 3.1-4.9 kg on the different plots. The amount of sown clover present in the pasture accounted for 77 per cent of the between-plot variation in fleece weight and 66 per cent of the between-plot variation in annual liveweight gain. Measurements of pasture growth were made for four pasture mixtures. Total pasture growth showed differences of over 50 per cent due to pasture mixture, yet, when grazed at 20 weaners per hectare, differences in annual liveweight gain and fleece weight (10 months wool), due to pasture mixture, did not exceed 10 per cent. Annual liveweight gain and fleece weight were not correlated total pasture growth. However, pasture growth rate measured at monthly intervals, accounted for 43 per cent of the variation in mean daily liveweight gain during these individual months.