FORTIFICATION OF CALF MILK REPLACERS WITH AMINO ACIDS IN FREE FORM OR PLASTEIN-BOUND

Abstract

Calves (eight per lot), from 3 to 45 days of age, were fed milk replacer containing skim powder, whey, and soy protein; or skim powder, whey, and blood protein; or skim, whey control diet. Additional treatments included supplementation of the soy and blood diets with the calculated-limiting amino acids (CLAA) either in the free form, or bound to the soy or blood proteins by the plastein reaction in an attempt to enhance utilization of the supplemental amino acids. Supplementation of the soy and blood basal diets with either free or plastein-complexed CLAA increased average daily gain (ADG), feed intake, and feed efficiency, with the free and plastein-bound CLAA giving approximately the same improvements. Additionally, the low blood plasma levels of CLAA for the soy and blood protein basal groups were increased to a similar extent by supplementation with free or plastein-bound CLAA. Only the skim milk control diet clotted, in vitro, on addition of rennet (pH 6.1). It is suggested that the plastein-bound and free, supplemental CLAA gave similar improvement in calf performance either because all sources of amino acids were absorbed at similar rates, or alternatively, because the calf does not require absorption of all essential amino acids at closely similar rates for efficient utilization in body protein synthesis. Key words: Calves, milk replacers, plastein