Lambs may be deficient in vitamin E yet growth performance be normal
Take Home Message: Higher supplementary levels of vitamin E are required in lambs fed concentrates compared to grass silage, and lamb growth rate is a poor indicator of vitamin E status.
Dietary vitamin E level did not affect lamb performance, but those fed grass silage grew more slowly and had a higher feed conversion ratio than those fed concentrates. Just some of the findings of a trail, carried out by UK scientists, in order to determine the effect of dietary vitamin E level and basal diet on vitamin E status, performance and tissue fatty acid content in lambs.
“Vitamin E deficiency is associated with white muscle disease in lambs, but low levels can also reduce the shelf life of the meat” said the University of Bristol’s Eleni Kasapidou, explaining the rationale behind her work. Five groups of eight Suffolk cross Charolais wether lambs, with an initial live weight of 28.4kg, were allocated to one of five concentrate-based diets supplemented with all-rac α -tocopheryl acetate to contain 30mg, 60 mg, 120mg, 250mg, or 500mg of α-tocopheryl acetate per kilogram of dry matter for 63 days.
Two additional groups of eight lambs entered the study at 31.2kg and were fed grass silage and 400g/day concentrate for 56 days, with the whole diet providing the equivalent of 60mg or 500mg of α-tocopheryl acetate/kg DM. Lambs were weighed and blood samples were taken weekly.
“At day 0, plasma a-tocopherol concentrations were low 0.8mg/ml and did not differ between treatments,” said Dr. Kasapidou. “Plasma α -tocopherol concentrations then decreased in all lambs except for those fed grass silage, which increased.”
At slaughter, muscle and liver a-tocopherol concentrations were in the deficiency range for lambs fed 30mg, 60mg or 120mg, whereas plasma creatine kinase and tissue polyunsaturated fatty acids were unaffected by dietary vitamin E level.
“But creatine kinase levels were higher and glutathione peroxidise levels lower in lambs fed grass silage compared to concentrates alone,” said Dr Kasapidou. “Muscle and liver α -tocopherol concentrations were 1.8- and 4.1-fold higher in lambs fed silage and 60mg of α-tocopheryl acetate than those fed 60mg of α-tocopheryl acetate alone.
“But there was less of a difference between lambs fed silage and 500mg/kg DM of α-tocopheryl acetate or just 500mg α-tocopheryl acetate in the concentrate, with muscle and liver differences of 0.4- and 0.7-fold, respectively.
“Tissue n-3 polyunsaturated fatty acid concentrations were higher and n-6 fatty acids lower in lambs receiving the grass silage compared to concentrate-based diets, but were not affected by dietary vitamin E level,” she added.
“Lower plasma and tissue levels of a-tocopherol are present in lambs supplemented with all-rac-α-tocopheryl acetate on a concentrate compared to a mixed diet of silage and concentrates, although growth can be achieved at tissue levels previously considered to represent deficiency, and this may affect the subsequent shelf life of the meat.”
Kasapidou E, Enser M, Wood JD, Richardson RI, Wilkinson RG and Sinclair LA: “Influence of vitamin E supplementation and basal diet on the vitamin E status, performance and tissue fatty acid concentrations in lambs.” Animal 3, 516-526
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