Salt (NaCl) use in New Zealand pastoral agriculture - a summary of recent trial results

Abstract

Milking cows in mid-season gave a 12.8% increase in milk yield when drenched with NaCl where herbage sodium (Na) levels were deficient (<0.05%), whereas at a herbage Na level of 0.10% in February, there was no milk yield response to salt supplementation. Dairy heifers growing at 1.0-1.6 kg liveweight gain/head/day at a herbage Na level of 0.05% and ad libitum pasture did not benefit from salt supplementation using salt blocks. An application of 100 kg NaCl/ha salt to pasture maintained Na levels in pasture for 5 months but in severely deficient situations up to 180 kg/ha may be required. Dusting pastures with salt or a salt/MgO combination prior to calving resulted in elevated herbage Na and magnesium (Mg) status from the dust adhering to the grass for up to 5 days after application. Mixing the two products improved handling and reduced the drift of dust when applied to the paddock. There is a range of methods for supplementing animals with sodium, all of which have their place, depending on the type of livestock enterprise. Keywords: dairy cows, dairy heifers, pasture, salt blocks, salt dusting, sodium