Summer-autumn rainfall effects on wool staple strength and position of break. I. Small-scale field simulations of rainfall onto sheep grazing dry pasture in February and April

Abstract

Despite a great deal of anecdotal evidence linking summer–autumn rainfall events to the position of break (POB) of wool from sheep grazed in a Mediterranean environment, there are no published experiments directly investigating this relationship. This trial examined the effects on staple strength (SS) and POB of simulated rainfall onto sheep grazing dry pasture residues during February and April. The simulated rainfall events had few significant effects on the wool quality parameters of the sheep in this trial. The natural rainfall associated with the ‘break’ of the season had a much greater influence on SS and POB.

A significant effect on POB was noted in the wool from sheep that had been exposed to simulated rainfall and then grazed germinating green pasture for approximately 15–20 days. The effect on POB could be an effect of the green feed alone or a combination of the green feed and simulated rainfall.

When grazing wetted dry pasture, sheep appeared to alter their grazing behaviour and showed more apparent ‘selectivity’. Overall grazing times did not appear to be affected and sheep in several treatment groups were observed to graze whilst their rainfall simulations were in progress. Wetting of dry pasture also appeared to increase the ‘toughness’ of the plant material available.