Dietary cation–anion differences in some pasture species, changes during the season and effects of soil acidity and lime amendment
Sophie Pelletier A E , Richard J. Simpson B , Richard A. Culvenor B , Gilles Bélanger A , Gaëtan F. Tremblay A , Guy Allard C , Jörg Braschkat B D and Peter J. Randall BA Agriculture and Agri-Food Canada, Soils and Crops Research and Development Centre, Québec, QC G1V 2J3, Canada.
B CSIRO Plant Industry, PO Box 1600, Canberra, ACT 2601, Australia.
C Département de Phytologie, Faculté des Sciences de l’Agriculture et de l’Alimentation, Université Laval, Québec, QC G1V 0A6, Canada.
D Present address: Birkenweg 49, 69221 Dossenheim, Germany.
E Corresponding author. Email: pelletiers@agr.gc.ca
Australian Journal of Experimental Agriculture 48(8) 1143-1153 https://doi.org/10.1071/EA08121
Submitted: 10 April 2008 Accepted: 22 May 2008 Published: 14 July 2008
Abstract
The difference between cation and anion concentrations is an important property when assessing feed for dry dairy cows in order to avoid hypocalcaemia following calving. Dietary cation–anion difference (DCAD) is used to assess suitability of feed and predict the risk of milk fever; a value of –5 cmol(+)/kg dry matter (DM) or less is desirable. This work has examined the DCAD of 16 field-grown species found in pasture in southern Australia. The DCAD [cmol(+)/kg DM] at the flowering stage varied from 7 to 32 for grasses, 21 to 72 for legumes and 72 to 99 for dicot weeds. The average DCAD for legumes was 50 cmol(+)/kg DM, over 2-fold higher than the 20 cmol(+)/kg DM average for grasses. There was a substantial decline in DCAD of herbage as the season progressed. In a glasshouse experiment with five grass species in an acid soil, lime application increased yield and tended to lower the DCAD. Lime decreased uptake per unit root length of potassium and chlorine and increased uptake of calcium by phalaris and timothy. While DCAD is an important attribute of herbage for assessing its suitability for prepartum diets of dairy cows, the present data indicate that it would be prudent to also consider concentrations of calcium and other mineral nutrients in herbage, particularly when examining less familiar plant species or the effects of different cultural practices on the composition of herbage for such diets.
Additional keywords: aluminium, developmental stage, harvest.
Acknowledgements
The authors would like to acknowledge the technical assistance of David Marshall, Adam Stefanski and Scott McDonald in the pot experiments and Patricia Wallace for XRFS analyses. Sophie Pelletier thanks CSIRO for hosting her visit and acknowledges the financial support of Fond québécois de la recherche sur la nature et les technologies, NOVALAIT Inc., Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec and Agriculture and Agri-Food Canada.
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