Factors that influence milk cholesterol and lipid phosphorus: content and distribution.

Average cholesterol content of 356 raw milk samples was 152.2 mug/ml and upon centrifugation (3000 X g for 8 min), 16.9% was distributed in the skim milk phase. Lipid phosphorus averaged 19.0 mug/ml and was partitioned 50:50 between cream and skim milk phases. Weight ratios of cholesterol to lipid phosphorus for milk and skim milk were 8.30:1 and 2.94:1. When variation due to milk yield, fat percent, and somatic cell numbers (deoxyribonucleic acid percent reflectance) was accounted for by least squares, cholesterol content and distribution did not differ among breeds (Holstein, Jersey, and Guernsey). Breed differences in lipid phosphorus content of whole milk could not be detected. However, Holsteins had a significantly lower content of lipid phosphorus and a higher weight ratio for skim milk. Milk yield, fat content, and somatic cells affected responses of cholesterol and lipid phosphorus. This supports a multiple origin concept for membrane material in skim milk.