Milk yield response following sodium chloride supplementation of cows grazing a tropical grass-legume pasture

Abstract

Twenty cows in early- to mid-lactation were used in a 12-week experiment to determine the effect of Na supplementation on milk yield. All cows were fed 1 kg maize/cow day-1 and half received 40 g coarse salt/cow day-1. There was an immediate response in milk yield to Na supplementation. Average yields over the 12-week period were 10.8 and 12.0 kg/cow day-1 (P< 0.05) for the unsupplemented and Na supplemented groups, respectively. At the start of the experiment, the mean saliva Na levels of 88.6 ± (S.D.) 4.9 mmol l-1 indicated that all cows were deficient in Na. Saliva Na levels in the supplemented group had returned to normal (> 145 mmol l-1) by week nine of the experiment.