Effect of herbage species on gastro-intestinal roundworm populations and their distribution

Abstract

Sheep faeces containing strongylate eggs were applied to plots of perennial ryegrass, prairie grass, or chicory mixed with white clover, or lucerne without white clover. Plots were later harvested within four height zones and the herbage mass, numbers, and species of gastro-intestinal nematodes determined. Ryegrass, prairie grass, and lucerne plots produced similar yields of herbage dry matter (DM) (3580, 3180, and 3230 kg DM/ha respectively), whereas chicory produced 2250 kg DM/ha. Ryegrass-, prairie grass-, and chicory-based swards had similar proportions of herbage DM within each height zone, the quantities declining with increasing height. Lucerne swards had less DM in the central height zones than other swards but proportionally more above 125 mm from ground-level. Larvae from 0.73% of eggs were recovered, but the rate was influenced by herbage species. The grass-based swards had higher larval populations than had lucerne or chicory, and lucerne had more than chicory. Larval density tended to be higher in the 26-75 and 76-125 mm zones than in the 0-25 and greater than 125 mm zones, which were similar. Chicory swards offered the best opportunity to reduce larval intake in grazing animals as they had the lowest populations per unit of herbage mass. This was, however, associated with a lower herbage mass. Lucerne offered low larval populations together with high nutritive value and herbage mass making it a highly suitable forage for growing lambs. © 1993 Taylor & Francis Group, LLC.