EFFECTS OF MILK-COMPOSITION AND PRODUCTION ON THE FEED COSTS OF PRODUCING MILK

The economic effects of changing the milk producing characteristics of dairy cows were evaluated. Special emphasis was on milk composition. Energy requirements for formation of the different milk components were derived from theoretical energy efficiencies of the formation of fat, protein, and lactose of milk along with current National Research Council recommendations and the gross energy content of milk components. Metabolizable energy requirements for formation of 1 g of fat, protein, and lactose were 16.3, 8.5, and 6.6 kcal. Under the present milk pricing system and assumed feed costs, the approximate change in income over feed costs expected from a .1% increase in either fat, protein, or lactose content of milk for a lactation of 7272 kg was +$12.78, −$2.51, and −$1.95. Such returns are indicative of the economic weights to put on milk solids in the development of selection indices under the present pricing system. © 1979, American Dairy Science Association. All rights reserved.