Dietary Cation–Anion Difference of Forage Species after Chloride Fertilization

Abstract

The dietary cation‐anion difference (DCAD), an indicator of hypocalcaemia risk in dairy cows, has been shown to be decreased by Cl fertilization in a limited number of forage species. Our objective was to assess the response of eight forage species grown in eastern Canada to two Cl fertilization treatments (0 vs. 90 + 50 kg Cl ha−1 applied in early spring and after the first harvest, respectively). Alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), smooth bromegrass (Bromus inermis Leyss.), meadow bromegrass (Bromus biebersteinii Roemer and J.A. Schultes), tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire], timothy (Phleum pratense L.), reed canarygrass (Phalaris arundinacea L.), and Kentucky bluegrass (Poa pratensis L.) were seeded in 2 yr at one location and harvested twice in the first post‐seeding year of each seeding. The experimental design was a split‐plot with four replicates; species as main plots and Cl fertilization as subplots. Chloride fertilization decreased the DCAD [(Na+ + K+) – (Cl− + S2–)] of all forage species; this decrease ranged from 78 (smooth and meadow bromegrasses) to 201 mmolc kg−1 dry matter (DM) (reed canarygrass) in spring growth and from 88 (Kentucky bluegrass) to 269 mmolc kg−1 DM (tall fescue) in summer regrowth. Species differed in their DCAD with legume species having the highest and timothy, reed canarygrass, and Kentucky bluegrass having the lowest. Producing forage with a DCAD lower than 250 mmolc kg−1 DM is possible without Cl fertilization in Kentucky bluegrass and with Cl fertilization in timothy and reed canarygrass.