Dietary cation anion difference of five cool-season grasses

• Published in: Agronomy journal Vol. 98; no. 2; pp. 339 - 348
• Main Authors: Tremblay, G.F, Brassard, H, Belanger, G, Seguin, P, Drapeau, R, Bregard, A, Michaud, R, Allard, G
• Format: Journal Article
• Language: English
• Published: Madison American Society of Agronomy 01.03.2006
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; cool season grasses; cultivars; dietary cation anion difference; forage crops; forage grasses; Fundamental and applied biological sciences. Psychology; milk fever; mineral content; nutritive value; potassium; seasonal variation; Quebec; Monocotyledones; Anions; Diet; Gramineae; Agronomy; Angiospermae; Spermatophyta; Cations; C3-Type
• ISSN: 0002-1962; 1435-0645
• DOI: 10.2134/agronj2005.0161

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 Quebec, 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 [DCAD(S) = (Na(+) + K(+)) - (Cl(-) + S(2-))], and a long equation [DCAD(L) = (Na(+) + K(+) + 0.15Ca(2+) + 0.15Mg(2+)) - (Cl(-) + 0.6S(2-) + 0.5P(3-)). The five species had, respectively, DCAD(S) of 656, 540, 510, 490, and 384 mmol(c) kg(-1) DM (dry matter) in spring growth, and 633, 569, 496, 447, and 332 mmol(c) 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 DCAD(S) (by 52 mmol(c) kg(-1) DM) and DCAD(L) (by 35 mmol(c) kg(-1) DM) from spring growth to summer regrowth. Cultivars did not differ in DCAD(S) and DCAD(L) 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.