Milk Energy Yield and the Correlation between Fat Percentage and Milk Yield

Abstract

The theory that milk yield, so far as affected by fat percentage (or milk composition), is inversely proportional to milk energy per unit of milk (or milk-energy yield is independent of milk composition) is used to develop the expected coefficient of correlation between fat percentage and milk yield, rMf. On this theory it develops that −r Mf= Vf VMf¯ 223+f¯, where V is variability and f¯ is mean fat percentage. For Vf/VM=.4 (the usual value as rMf has been generally derived) and f¯=4 the formula gives rMf=−24. The low value of rMf found in practice is in keeping with the constant energy theory, and does not detract from its biological significance or warrant its neglect in a practical breeding philosophy. © 1940, American Dairy Science Association. All rights reserved.