Effect of coal mine pit water on the productivity of cattle. II. Effect of increasing concentrations of pit water on feed intake and health

Abstract

The effect of drinking high mineral content coal mine pit water on the health and growth of yearling tropically adapted steers was investigated. Steers consumed town water (~ 30 mg sulfate/L) or dilutions of pit water, which at the highest concentration contained (mg/L) 4000 sulfate as well as 3082 chloride, 328 calcium, 562 magnesium, 2600 sodium, and other minerals at lesser concentrations (total dissolved solids, 8600 mg/L). The growth and performance of the steers were measured as average daily weight gain, dry matter intake, faecal dry matter content, and water intake. Health was assessed using haematological indices (packed cell volume, haemoglobin, and others) and on randomly selected animals, by complete post mortem haematological and biochemical analysis. Consumption of diluted pit water of up to 2000 mg sulfate/L, if introduced gradually, did not result in a reduction in dry matter or water intake. Significant interactions (P < 0·05) occurred between rate of introduction and plane of nutrition in affecting weight gain, whereby weight gains on pit water were marginally greater when treatment was introduced abruptly. Plane of nutrition was the main effect in determination of packed cell volumes, where low plane of nutrition led to higher values. Interactions of time on pit water treatment with rate of introduction or nutrition in affecting packed cell volume were statistically significant (P ≤ 0·006) but small in magnitude (1–2%), and hence unlikely to be biologically significant since averages remained within the normal range for the age group. Pit water treatment did not compromise the animals’ health at 2000 mg sulfate/L, as assessed by visual veterinary and histopathological examinations of tissues taken at autopsy. When the concentration of pit water was increased to 4000 mg sulfate/L, dry matter intake was depressed by 14% and water intake was decreased by up to 40%, increasing slightly with longer time on treatment. Under the conditions of this experiment, beef steers can drink coal mine pit water containing up to 2000 mg sulfate/L (4000–6000 mg/L of total dissolved solids) without suffering ill effects, provided that it is introduced gradually. The study therefore provides evidence that the recommendation of 1000 mg sulfate/L as the maximum concentration in livestock drinking water may be too conservative for steers if favourable conditions exist.