Zinc supplementation of lactating ewes and weaned lambs grazing improved mediterranean pastures

Abstract

The effects of post-partum supplements of zinc (Zn) on the Zn status and growth of 40 ewes and their newborn lambs grazing grass-clover pastures were studied. A control group received no supplemental Zn; supplemented ewes received Zn as an intra-ruminal Zn pellet and lambs received a Zn pellet at weaning followed by an oral Zn drench. Zinc concentrations in pastures ranged from 10 mg/kg in autumn to >20 mg/kg in winter. Zinc supplementation increased the concentration of Zn in milk but had no effect on Zn in plasma or wool of ewes or lambs and no effect on weight gain or wool production. Zinc supplements had no adverse effects on the copper concentration of tissues or milk. Zinc supplied as pellets increased the activity of glutathione peroxidase in blood. The results indicate that, at least when pasture quality and quantity is too poor for sheep to gain weight, Zn requirements for growth and wool production of lactating ewes and lambs can be met on pastures containing 10-20 mg Zn/kg.