Sarah Ann Smith

Document Type

Honors Project

First Advisor

Dr. Ellen Mitchell

Degree Award Date

Spring 1998

Keywords

HPLC Analysis, Beta-carotene, vitamin A, milk, Guernsey cows, Holstein cows, Guernsey-Holstein hybrid cows

Disciplines

Animal Sciences | Chemistry | Dairy Science

Abstract

Beta-carotene is produced only by plants; after its consumption by animals it is converted to vitamin A and stored in fat as retinol palmitate. Vitamin A is an essential vitamin that plays a role in cell differentiation, the loss of which is a basic feature of cancer. While vitamin A is beneficial in small amounts, it can be toxic in large doses. Beta-carotene is less potent, is less toxic, and, through its antioxidant activity, confers protection against several types of cancer. Beta-carotene and retinol palmitate are present in the fat of cows' milk, in varying concentrations within and among breeds. Previous studies have examined breed differences in the beta-carotene and retinol palmitate content of cows' milk, but those studies have been limited by small sample sizes, confounding effects of feed differences, or lack of statistical analyses. In this research, diet and housing conditions were held constant for four genetically different groups of cows. Milk from purebred Guernsey cows, purebred Holstein cows, and two types of Guernsey-Holstein hybrid cows was analyzed with HPLC to assess the beta-carotene and retinol palmitate content. The Guernsey milk fat consistently contained more betacarotene (p < 0.001) than Holstein milk fat, suggesting that selecting Guernsey milk might be beneficial for human health. The differences in retinol palmitate content varied; either no differences were found, or the Guernsey milk fat contained less (p < 0.05). The hybrid cows generally produced more beta-carotene than the Holstein cows, leading to the possibility of selective breeding through outcrossing the Holstein cows with Guernsey cows to result in higher quality milk.

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