Effect of Phosphorus Deficiency on Metabolism of Carotene and Vitamin A by Beef Cows

Abstract

Nine bred Hereford cows, after a preliminary period of low-phosphorus intake, were used to study the effect of phosphorus deficiency on carotene metabolism. For an average period of 8 weeks before calving and 8 weeks or longer thereafter, four of the cows were continued on the low-phosphorus ration and five were given a phosphorus supplement. All of the cows received equal but limited amounts of carotene supplied by prairie hay. Determinations were made of the phosphorus content of the plasma and the carotene and vitamin A content of the plasma, liver, and milk of the cows at regular intervals. Average plasma-carotene levels were generally higher in the phosphorus-deficient cows than in those fed adequate phosphorus; these differences approached statistical significance (5% level). Plasma-vitamin A levels appeared to be unaffected by phosphorus deficiency. At 8 weeks after calving both groups of cows had lost similar amounts of carotene and vitamin A from the liver. Milk from the phosphorus-deficient cows contained more carotene but less vitamin A than that from the cows fed adequate phosphorus. Copyright © . .