Dietary Cation Anion Difference of Five Cool‐Season Grasses

Abstract

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 Qué bec, 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 5 (Na 1 1 K 1 ) 2 (Cl 2 1 S 22 )], and a long equation [DCAD L 5 (Na 1 1 K 1 1 0.15Ca 21 1 0.15Mg 21 ) 2 (Cl 2 1 0.6S 22 1 0.5P 32 ). The five species had, respectively, DCAD S of 656, 540, 510, 490, and 384 mmol c kg 21 DM (dry matter) in spring growth, and 633, 569, 496, 447, and 332 mmol c kg 21 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 21 DM) and DCAD L (by 35 mmol c kg 21 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.

Dietary cation - anion differences in some pasture species, changes during the season and effects of soil acidity and lime amendment

“…The strong relationship between K concentration and DCAD is consistent with earlier work on herbage grasses DCAD Tremblay et al 2006;Pelletier et al 2006Pelletier et al , 2007aPelletier et al , 2007b. In the subset of species sampled over the growing season (Fig.…”

“…This could be partly due to the stage of development that was earlier (early-to mid-heading stage) in the experiment from Tremblay et al (2006) compared with the present experiment (flowering stage).…”

“…The mineral balance and DCAD of herbage is known to be strongly influenced by the species in the pasture and the timing of the harvest in the growing season (Braschkat and Randall 2004;Tremblay et al 2006;Pelletier et al 2007a). In addition, fertiliser application can have a substantial effect on DCAD (Pelletier et al 2007a).…”

Timothy mineral concentration and derived indices related to cattle metabolic disorders: A review

“…The GT index was lower for timothy than for orchardgrass by 0.9 in the spring growth and by 0.8 in summer regrowth when calculated from data reported by Tremblay et al (2006), but was similar for both forage species at both harvests when calculated from data reported by Gervais (1991).…”

“…Tremblay et al (2006), in a multi-site study in eastern Canada, reports generally low or intermediate K, Na, Ca, and Mg concentrations in timothy compared with orchardgrass, meadow bromegrass (Bromus biebersteinii Roemer & J.A. Schultes), tall fescue [Lolium arundinaceum (Schreb.)…”