Backgrounding lambs on saltbush provides an effective source of Vitamin E that can prevent Vitamin E deficiency and reduce the incidence of subclinical nutritional myopathy during summer and autumn

Abstract

Vitamin E deficiency is common in sheep during summer and autumn in Mediterranean environments because of the lack of green feed. Deficiency of Vitamin E can lead to the development of nutritional myopathy, a condition causing heart and skeletal muscle damage which, in severe cases, can lead to death of the animal. Saltbush (Atriplex spp.) contains high concentrations of Vitamin E, so providing sheep with access to saltbush during summer may improve their Vitamin E status and prevent Vitamin E deficiency. We wished to determine whether backgrounding lambs on saltbush over summer and autumn (i.e. graze saltbush-based pastures for several weeks before finishing them to condition suitable for slaughter) would prevent Vitamin E deficiency and nutritional myopathy and compared the effectiveness of this strategy in preventing Vitamin E deficiency to a commercially available synthetic Vitamin E supplement. Ten-month-old cross-bred lambs (n = 48) were backgrounded on dry, senesced (control) or saltbush-based pastures for 8 weeks during summer. After backgrounding they were fed a grain-based finishing ration containing low levels of Vitamin E for a further 5 weeks. We found that while grazing saltbush the plasma Vitamin E concentrations of lambs increased from 1.1 to 2.6 mg/L within 3 weeks, concentrations that were significantly higher than the concentrations in the lambs that did not have access to saltbush during backgrounding (P < 0.001). The improved Vitamin E concentrations corresponded with a reduction in the incidence of nutritional myopathy, with none of the lambs grazing saltbush showing any biochemical signs of myopathy, whereas 17% of lambs backgrounded on control pastures had elevated plasma concentrations of creatine kinase that were indicative of subclinical nutritional myopathy. During the subsequent finishing phase, lambs that had not had access to saltbush during backgrounding were all Vitamin E deficient and, of these, 8.5% were diagnosed with subclinical nutritional myopathy. By contrast, none of the lambs backgrounded on saltbush was Vitamin E deficient nor did they have any biochemical evidence of Vitamin E-responsive myopathy. The present study demonstrated that saltbush is a valuable source of Vitamin E for livestock that can reduce the incidence of subclinical nutritional myopathy in lambs during summer and prevent plasma Vitamin E concentrations becoming deficient for up to 5 weeks after saltbush is removed from the diet.