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This article in AJ

  1. Vol. 98 No. 2, p. 339-348
    Received: May 25, 2005

    * Corresponding author(s): tremblaygf@agr.gc.ca


Dietary Cation Anion Difference of Five Cool-Season Grasses

  1. Gaëtan F. Tremblay *a,
  2. Hélène Brassardb,
  3. Gilles Bélangera,
  4. Philippe Seguinc,
  5. Raynald Drapeaud,
  6. Annie Brégardb,
  7. Réal Michauda and
  8. Guy Allardb
  1. a Agriculture and Agri-Food Canada, Soils and Crops Research and Development Centre, 2560 Hochelaga Blvd, Sainte-Foy, QC G1V 2J3, Canada
    b Département de Phytologie, Faculté des sciences de l'agriculture et de l'alimentation, Université Laval, Sainte-Foy, QC G1K 7P4, Canada
    c Dep. of Plant Science, Macdonald Campus, McGill Univ., 21111 Lakeshore Rd., Sainte-Anne-de-Bellevue, QC H9X 3V9, Canada
    d Agriculture and Agri-Food Canada, Soils and Crops Research and Development Centre, Research Farm, 1468 St. Cyrille Street, Normandin, QC G8M 4K3, Canada


Forage-based rations with a low dietary cation anion difference (DCAD) should be fed to dairy cows 2 to 4 wk prepartum to prevent hypocalcaemia or milk fever. We evaluated the DCAD of two to four cultivars of five grass species at three locations in Québec, Canada. Orchardgrass (Dactylis glomerata L.), meadow bromegrass (Bromus riparius Rehmann), tall fescue (Festuca arundinacea Schreb.), smooth bromegrass (Bromus inermis Leyss.), and timothy (Phleum pratense L.) were harvested twice a year during two production years. Forage mineral concentrations were measured and the DCAD was calculated with a short equation [DCADS = (Na+ + K+) − (Cl + S2−)], and a long equation [DCADL = (Na+ + K+ + 0.15Ca2+ + 0.15Mg2+) − (Cl + 0.6S2− + 0.5P3−). The five species had, respectively, DCADS of 656, 540, 510, 490, and 384 mmolc kg−1 DM (dry matter) in spring growth, and 633, 569, 496, 447, and 332 mmolc kg−1 DM in summer regrowth. Orchardgrass had the highest DCAD and timothy the lowest while the three other species were intermediate in both spring growth and summer regrowth. Species differences in DCAD were primarily related to differences in K concentration. Timothy was the only species that decreased significantly in DCADS (by 52 mmolc kg−1 DM) and DCADL (by 35 mmolc kg−1 DM) from spring growth to summer regrowth. Cultivars did not differ in DCADS and DCADL except for tall fescue. Locations did not differ in DCAD. Among the grass species in this study, and because of its low DCAD, timothy is the best suited for producing forages fed to dairy cows in the weeks preceding calving.

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