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The Effect of Breed Characteristics and the Plane of Nutrition of the Cow on the Vitamin A Potency of Milk^*

Department of Dairy Husbandry

N. B. Guerrant and R. A. Dutcher

Department of Agricultural and Biological Chemistry, The Pennsylvania State College

ABSTRACT

The natural pigmentation of milk produced by various breeds of dairy cattle under comparable conditions is known to vary with different breeds. The Guernsey and the Jersey breeds produce a more highly pigmented milk than do the cows of the Holstein, Ayrshire, and Brown Swiss breeds. This yellow color is restricted almost entirely to the milk fat and is due primarily to carotene. Since carotene is now recognized as a precursor of vitamin A, it would seem logical to postulate that butter made from Guernsey or Jersey milk should possess greater vitamin A potency than butter made from the milk of the Holstein, the Ayrshire, or the Brown Swiss breeds. Furthermore, Jersey and Guernsey milks, in addition to having a higher color value, also have a higher average fat content. In view of these facts, it would appear that there should be a difference in the vitamin A potency of these milks, especially if carotene alone is responsible for this biological activity.

^* This investigation was supported in part by a grant from the Pennsylvania Federation of Holstein-Friesian Clubs.

The data presented in this paper were taken from a thesis submitted by Alfred O. Shaw as one of the requirements for the degree of Doctor of Philosophy in the Graduate School of the Pennsylvania State College.

Authorized for publication on March 17, 1937, as paper No.764 in the Journal Series of the Pennsylvania Agricultural Experiment Station.