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

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 10 lb. until partially depleted of their vitamin A stores.When the average plasma vitamin A concentration was 8.0 ± 1.8 7 per 100 nil., 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-y, for one of two durations, 4-or 16-wk.Each calf was then changed to one of two final period carotene intakes, 60-or 240-7 .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 12-7 carotene intake had cerebrospinal fluid pressures above 120 mm. of saline.During the terminal seven-day period of the 12-wk.final carotene intake period, those calves fed the 12--/ initial period carotene intake and the 60-y final period carotene intake had pressures greater than 120 mm.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 12-7 initial carotene period intake for 16 wk.utilized the 60-and 240-7 carotene intakes 0.6 to 0.8 as effectively as calves fed 48-7 carotene intake initially.While the differences between the 12-and 48-7 carotene for the 4-wk.duration were slight, across both the 4-and 16-wk.durations, calves fed the 12-y intake utilized carotene between 0.7 and 0.9 as efficiently as calves fed the 48-~ intake.Cattle are subjected, at times, to periods of suboptimum carotene intake which, if continued, result in vitamin A deficiency.There is some evidence to indicate that cattle fed deficient carotene intakes for extended periods of time, or cattle fed carotene-free rations and exhibiting extremely low plasma and liver vitamin A concentrations, do not utilize carotene as efficiently as cattle previously fed rations adequate with respect to carotene intake.