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Availability of Vitamin A and Carotene as Influenced by Soft Phosphate¹

University of Arizona,² Tucson

Abstract

In vitro studies of the adsorption of vitamin A, carotene and alfalfa pigments by soft phosphate with colloidal clay gave the following results. Either a decrease in particle size or an increase in the amount of soft phosphate, increased carotene adsorption. Soft phosphate adsorbed all pigments from a petroleum ether extract of alfalfa in the absence of acetone. Nearly all alfalfa pigments except carotene could be released from the soft phosphate by acetone treatment. A blue color was formed on the phosphate when it was treated with a petroleum ether solution of vitamin A; acetone treatment released the blue color and produced a yellow supernatant. The binding capacity of phosphate was influenced by its moisture content.

Soft phosphate, bone meal and dicalcium phosphate were compared as sources of supplemental phosphorus for sheep. Soft phosphate depressed weight gains and feed utilization. The inactivation of dietary vitamin A by soft phosphate was indicated by the magnitude of hepatic vitamin A loss in a 45-day period.

¹ Arizona Agricultural Experiment Station Technical Paper No. 444. Throughout this paper the term "soft phosphate" refers to the commercial feeding grade of soft phosphate with colloidal clay.

² Department of Animal Science.