Protein Content in Raw and Fluid Milk Products1

Abstract

Protein values of more than 100,000 individual cow samples of milk were determined over a 12-month period. In addition, protein levels of more than 1,100 store-purchased samples of whole, lowfat and skimmilk were determined during 27 months. Protein determinations were made with an automatic Foss Combi protein-fat tester, which is in regulaur use at the Pennsylvania Dairy Herd Improvement Central Milk Testing Laboratory. Lactation averages indicate wide differences among breeds for percentage of protein and total yield. Identification of cows with high fat yield does not assure identification of those cows with high protein yield. Seasonal variations were noted for raw milk and retail samples of fluid milk. Average protein content of retail whole milk samples was 3.26%, but levels ranged from 2.82% to 4.20%. Protein content of low fat milk varied depending on the level of fortification with non-fat milk solids.