The effect of sodium chloride supplementation of a sodium adequate hay on digestion, production and mineral nutrition in sheep

Abstract

SUMMARYFour groups of six 18-month-old wethers were fed a diet of hay ad libitum with a pelleted ground barley supplement for 70 days. The control group received no further dietary supplements and the sodium content (0·46%) was above that recommended by published standards. Groups 2, 3 and 4 received supplements of sodium chloride, mixed and pelleted with the barley, to provide a final dietary concentration of 1·7, 2·5 and 3·1% sodium respectively.Dry-matter intake, dry organic-matter intake and digestible organic matter in dry matter (DOMD) were significantly reduced (P < 0·01) at the highest sodium intake. There was a reduction in live-weight gain and efficiency of utilization of digestible organic matter with increasing sodium chloride supplementation, with significant differences (P < 0·05) between the highest and lowest sodium intake groups.There were no consistent or significant changes in the serum concentrations of sodium or potassium following sodium chloride supplementation, but serum calcium and magnesium levels were significantly lowered as a result of sodium chloride supplementation.Sodium chloride supplementation improved the apparent availability of sodium, potassium, magnesium and calcium but reduced that of phosphorus and nitrogen. The retention of Na, K, Mg, P and N was lower at the highest sodium intake but Ca retention was higher. Urine volume and excretion of Na, K, Mg, Ca, P and N increased with sodium chloride intake.