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The relationship between digestibility and clover content of dairy pastures in the Adelaide hills

M.J. Cochrane and E.D. Carter

South Australian Department of Agriculture, G.P.O. Box 1671, Adelaide SA 5001
The University of Adelaide, Waite Agricultural Research Institute, Glen Osmond SA 5064

Introduction

It is generally considered that the higher clover content of pastures is associated with higher nutritive value and subsequent animal production due to intakes of digestible dry matter (DDM) and crude protein As part of a survey to establish the productivity of subterranean clover-based pastures in the higher rainfall areas of the Adelaide Hills (1), digestibility analyses (2) were carried out on the clover, grass and weed components of pastures harvested during the spring of 1985 and 1986 and unweighted linear regressions determined on the relationships between DDM and per cent clover in the sward.

Methods

In September 1985 and 1986, herbage cut from a 0.4 m2 quadrat inside five exclosure cages at 10 sites in the Adelaide Hills was manually separated into clover, grass and weed components. Samples were oven dried at 100C for 12 h and weighed, and dry matter percentages and plant component yields and percentages calculated.

Results and discussion

In 1985 there was no significant relationship between DDM percentage and clover percentage, but in 1986 DDM was negatively correlated to clover percentage (DDM% = 69.6-0.059 clover %, P<0.05). When the data from both years were combined the relationship was significant at the 1% level (DDM % = 68.6-0.041 clover %) although scatter of the data is large in both years. The relationship draws attention to the lower DDM content of subterranean clover pastures. However, it should be emphasised that these results for DDM apply to the green pasture. After plant senescence there is ample evidence that dry clover and grass residues have reduced digestibility which affects animal production.

Acknowledgements

This project was part-funded by the Dairy Research and Development Corporation. The assistance of Ms Lynne Giles, Statistical Consultant, Waite Agricultural Research Institute is gratefully acknowledged.

References

Carter, E.D. and Cochrane, M.J. 1985. Proc. 3rd Aust. Agron. Conf., Hobart. p.217

Tilley, J.M.A. and Terry, R.A. 1963. J. Br. Grassld Soc. 18, 104-111.

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