Composition of the diet of sheep grazing swards of differing white clover content and spatial distribution

摘要

Abstract Thirty swards containing either alternating strips of pure grass and pure clover or mixed grass and clover were developed by herbicide treatment to give nominal white clover proportions of 10, 30, 50, 70, and 90%. Diet selection was estimated in 3 periods using both oesophageally fistulated sheep and pre- and post-grazing cuts to determine the effect of spatial distribution and white clover content of the sward on diet content. Clover in the sward varied from 1.1 to 90.4%. White clover was intensely selected in Period 1 in both mixed and strip swards because clover leaves overtopped a canopy of mainly dead grass. There was no evidence for preferential selection of clover from mixed swards in Periods 2 and 3, but preference was shown on the strip swards. Preference for weed species was marked, with some being grazed to ground level. There was no correlation for either grass or clover between preference and sward content on mixed plots. This implies that sheep were grazing to optimise energy intake...