Changes of Protein Composition of Milk by Ratio of Roughage to Concentrate

Abstract

Lactating Holstein-Friesian cows were fed rations containing 40 to 60% concentrate with second-cut brome-alfalfa hay in a double reversal feeding experiment. Both rations were formulated according to National Research Council specifications to meet requirements for all nutrients and were similar in protein and caloric content. Milk samples were collected on the 10th day after the transition from one ration to the other and were analyzed for fat, protein, whey protein, casein protein, and for individual milk protein components. The latter were separated by diethylaminoethyl cellulose column chromatography. Milk protein content was .1% lower on the high concentrate ration. No other significant differences in milk composition could be attributed to change in ration. Variations in milk proteins among individual cows were greater than those attributed to change in diet.