A MULTI ELEMENT SUPPLEMENT FOR GRAZING SHEEP .1. INTAKE, MINERAL STATUS AND PRODUCTION RESPONSES

The safety and effectiveness of a loose mineral lick containing all known essential elements was investigated in an experiment in which 96 Merino weaner wethers grazed subterranean clover/grass pastures during. summer and autumn. The treatments were no supplement or mineral mix ad libitum; there were four plots of 12 sheep per treatment. The mean intake was 29 +/- 1 g/head per day of the mix and those offered the minerals had blood concentrations of P, S, Se and vitamin B-12 in the normal range. Unsupplemented Control sheep had blood concentrations of P, S and Se in the deficient range for all or part of the experimental period. There was an estimated 1.6-fold range in mineral intake between sheep, and none refused the mix. Concentrations of Cu, Cd and F in tissues and bone of sheep offered the mineral mix were within accepted safety margins. The mineral lick increased live weights by 4.5 kg during summer (P < 0.05), increased clean fleece weight by 240 g (9%), (P < 0.01), and increased wool staple strength by 15 N/kt (40%), (P < 0.01). The pasture concentrations of most macro elements decreased between November and March, respective concentrations being (g/kg DM): K, 17.7 and 1.9; Na, 4.0 and 0.31; S, 1.6 and 0.9; N, 12.9 and 10; P, 1.95 and 1.08; Ca, 7.86 and 9.75; Mg, 2.29 and 1.38. Changes in trace element concentrations were small, the respective values being (mg/kg): Cu, 9.7 and 10.3; Mn, 47 and 67; Fe, 56 and 323; Zn, 20 and 20; Mo, 0.2 and 0.35; and Se, 0.015 and 0.032. The loose mineral lick was a safe and effective means of supplying macro and trace elements to grazing sheep during summer.