Whole wheat grain feeding of Merino ewes. 4. Changes in hepatic vitamin A concentration

Abstract

In two experiments Merino breeding ewes were fed wheat in pens or small paddocks from joining to weaning. Three levels of wheat were examined in each experiment and at each wheat level one-half of the ewes received vitamin A, Injections of 1 million I.U. of vitamin A were given twice in the first experiment and four times in the second. Control groups of ewes were run at pasture or fed pasture hay. Ewes injected with vitamin A had higher hepatic concentrations of the vitamin than those unsupplemented. Wheat intakes, which ranged from 3.4-7.1 kg ewe-1 week-1, had no effect on either the rate of expenditure of hepatic vitamin A concentration or the extent of storage and absorption of the vitamin after dosing. Pregnancy and lactation did not significantly increase changes in hepatic vitamin A concentration. The relationship between hepatic vitamin A concentration and time was curvilinear in ewes fed wheat without vitamin A. The rate of loss was not different between experiments and amounted to 6.03 per cent per week.