Alpha-tocopherol, selenium and polyunsaturated fatty acid concentrations in the serum and feed of spring-calving dairy heifers

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Abstract
The objectives of this study were to provide baseline data for α-tocopherol, selenium and polyunsaturated fatty acid concentrations in the serum and feed of New Zealand dairy cattle, and to assess the likelihood that abnormal peroxide metabolism has a role in the impaired lactational and reproductive performance noted in selenium-deficient cattle. Twenty-four Friesian heifers were randomly allocated one of four winter diets consisting of hay with or without selenium supplementation, or pasture and silage with or without selenium supplementation. A winter diet consisting exclusively of hay (α-tocopherol concentration 19 mg/kg of dry matter) resulted in a pre-calving serum α- tocopherol concentration of 1.2 mg/l compared to 4.5 mgl for pastured heifers (p0.05). These results suggest that dairy cattle wintered on hay can become Vitamin E-depleted, whereas the feeding of pasture and silage should provide adequate Vitamin E. The pasture offered following calving during July and August provided a low dietary polyunsaturated fatty acid challenge, suggesting that abnormal peroxide metabolism is unlikely to be an important mechanism in the impaired performance of selenium-deficient adult cattle which calve at this time of year.