Influence of high zinc intakes, season, and staple site on the elemental composition of wool and fleece quality in grazing sheep

Abstract

The effect of high zinc (Zn) intakes on calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), phosphorus (P), sulphur (S), and Zn content of wool was studied in Romney wethers given no ZnO, 12 g Znf) weekly, or 12 g ZnO fortnightly for 12-months. The wool was sampled as a 12-month fleece or monthly from the midside. Dosing with 12 g ZnO weekly caused an immediate increase in the plasma Zn concentration from 0.5 to 2.6 μg/mlfollowed by a slow decrease to about 0.75 μg/ml after 7 days. The untreated sheep plasma remained at about 0.6 μg/ml.The concentrations of other plasma elements measured were not influenced by Zn intake. The Zn treatment increased the Zn concentration in the liquid phase (30000 g supernatant) of the digessta particularly in the abomasum and small mtestine. Most of the Zn dose was associated with the solid phase (30000 g pellet). The high Zn intakes caused a small, but non-significant, increase m the Zn content of the 12-month fleece even though the plasma Zn levels were elevated. The mean elemental composition of the wool (μg/g) was: Ca, 323; Cu, 2.9; Fe, 42; K, 3300; Mg, 59; Mn, 3.4; Na, 63; P, 120; and Zn, 114; whereas the S was 3.05%. Significant monthly changes in the concentrations of wool Na, K, Ca, Mg, P, S, Zn, Fe, and Mn were observed. The pattern of distribution of elements along the staple was dependent on the element. The concentrations of Na, K, P, and S were relatively constant along the staple whereas those of Ca, Mg, Zn, Fe, and Mn progressively increased from the skin to the tip of the staple, with the increase being most marked close to the tip. The increased Zn intake had no significant effect on the fleece weights, fibre strength, fibre diameter, bulk, and yellowness. © 1992 Taylor & Francis Group, LLC.