Effect of Duration of Deficient Carotene Intake upon Subsequent Utilization of Carotene from Alfalfa by Holstein Calves

Abstract

Summary Thirty-two Holstein male calves, approximately 63 days of age, were fed a vitamin A depletion ration at an intake to provide an anticipated seven-day increase in live weight of 10lb. until partially depleted of their vitamin A stores. When the average plasma vitamin A concentration was 8.0±1.8 γ per 100ml., each calf was then fed in addition to the vitamin A depletion ration, one of two initial period carotene intakes per pound of live weight per day, 12- or 48-γ, for one of two durations, 4- or 16-wk. Each calf was then changed to one of two final period carotene intakes, 60- or 240-γ. Durations for the final periods were either 24 wk. for the calves fed the initial period carotene intake for 4 wk., or 12 wk. for the calves fed the initial period carotene intake for 16 wk. During the terminal seven-day period of the initial 16-wk. carotene intake period, only those calves fed the 12-γ carotene intake had cerebrospinal fluid pressures above 120mm. of saline. During the terminal seven-day period of the 12-wk. final carotene intake period, those calves fed the 12-γ initial period carotene intake and the 60-γ final period carotene intake had pressures greater than 120mm. but of smaller magnitude than observed during the initial carotene intake period. Based upon blood plasma and liver vitamin A concentrations, determined on samples obtained terminally during the final carotene intake period, calves fed the 12-γ initial carotene period intake for 16 wk. utilized the 60- and 240-γ carotene intakes 0.6 to 0.8 as effectively as calves fed 48-γ carotene intake initially. While the differences between the 12- and 48-γ carotene for the 4-wk. duration were slight, across both the 4- and 16-wk. durations, calves fed the 12-γ intake utilized carotene between 0.7 and 0.9 as efficiently as calves fed the 48-γ intake.