Vitamin A status of heifers fed a diet deficient in Beta Carotene

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Introduction: Ruminants derive their retinol (vitamin A) requirements from β-carotene and generally have sufficient liver reserves to maintain healthy function through dry periods, but clinical vitamin A deficiency has been reported in cattle during prolonged drought (Hill et al. 2009). The level of endogenous reserves at which animals become symptomatic are unclear and manifestation of the disease seems highly variable (Jones et al. 1943). We characterised blood and liver retinol levels in growing heifers from a common background, systematically deprived of dietary β-carotene. Material and Methods: Yearling Braham heifers (n=30) were fed a β-carotene deficient diet consisting of wheaten straw ad. lib and a wheat-based pellet, throughout the trial. Blood was collected monthly, liver tissue biopsied every 90d and weight recorded weekly. Retinol concentrations were determined by HPLC. Results and Discussion: LW increased from 179kg (SEM 2.66 kg) at Od to 306kg (SEM 4.15kg) at 176d. Initi

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