Abstract

Detailed sward measurements made before and after grazing can detect the changes in mass and composition of vertical sward horizons which result from grazing. When animal species are grazed in mixtures, it is impossible, by this method to relate such sward changes to any one particular species. We estimated that quantitative importance of different sward horizons to the diet of cattle (CA), sheep (SA) and goats (GA) grazing alone or in a mixture; cattle with sheep (CS), sheep with cattle (SC) and cattle with goats (CG), goats with cattle (GC) in a progressive defoliation of ryegrass/white clover pasture. A least squares optimisation routine estimated the contribution of 5, 40mm sward horizons, each containing 6 botanical components to oesphageal extrusa (OE), containing the same 6 components, from each of the treatments. The results suggest that the diet of CA was more equally derived from horizons above 40mm than was that of SA which was concentrated in the 80- 120mm horizon. GA was intermediate. The contribution of the upper sward horizons to the CS diet was greater than for CA and SC moved lower down the sward horizons than SA. The mixing of goats and cattle had less effect on the relative contribution of the sward horizons to the diet selected than mixing sheep and cattle.

WB, McPherson, GC Cairns, WHD Leaning, and KM Newcomb

Proceedings of the New Zealand Society of Animal Production, Volume 49, , 307-313, 1989