Influence of green leaf distribution on diet selection by sheep and the implications for animal performance

P.J. L'Huillier, D.P. Poppi and T.J. Fraser

Ruakura Animal Research Station, Ministry of Agriculture and Fisheries, Hamilton; Lincoln College, Canterbury and Grasslands Division DSIR, Lincoln

Proceedings of the New Zealand Society of Animal Production. 1984, 44: 105-108

Diet selection from 2 swards (ryegrass and prairie grass) vertically stratified into 3 horizons (A, >6cm, B, 3 to 6 cm, C, 0 to 3 cm) was studied using oesophageally fistulated ewes in summer and autumn.

Green grass leaf (GGL) contributed 68 to 97% of diets, whilst pseudostem and dead material were rejected. Sward and dietary white clover contents were low in the sward and 0.1 to 4.9% in the diet) and no selection for this component was evident. Defoliation of white clover appeared to be influenced by the vertical distribution of GGL.

Green material distribution determined the horizons grazed. Sheep grazed horizon C of summer ryegrass pasture, where 95% of GGL was found. In all other swards the surface canopy (>3 cm above ground level) was composed primarily of GGL (>30%), and sheep grazed this horizon. Low apparent intake (21 g DM/kg live weight/d) was associated with the apparent need to penetrate the surface canopy to obtain GGL in summer ryegrass pasture.

Keywords: NZSAPAB; Sheep; green leaf; diet selection; white clover

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