Prediction of the Energy Value of Cow's Milk

Abstract

The quantification of lactation response requires that various yields of milk of various chemical compositions be equated to a common term.Although the gross energy value is the most common characteristic to which all organic substances can be reduced, its direct measurement is expensive.As a consequence, a study was made of the relationships among the energy value and the concentrations of total solids, solids-not-fat (SNF), fat, protein, lactose, and ash in 600 two-and seven-day composite samples of milk from 42 Holstein cows and ranging from 1.6 to 6.4% fat.An analysis of 21 different combinations of milk components showed that the most practical equation for the accurate prediction (C.V. = 1.3%) of the energy value of milks having a wide range of chemical composition is : Energy (kcal/lb) = 41.84 (% fat) + 22.29 (% SNF) --25.58.From this, the following equation was derived to compute the solids-corrected milk (SCM) yield containing 340 kcal of energy per pound: SCM (lb) = 12.3 (F) + 6.56 (SNF) --0.0752 (M); where F, SNF, and M are expressed as pounds of fat, solids-not-fat, and milk, respectively.This equation predicted the milk energy outPut of cows producing low-fat milk effected by dietary means as accurately as that of normal milk.The Gaines 4% FCM equation underestimated by as much as 15% the energy output in milk containing less than 3% of fat.To quantify the lactation response of cows, some expression is required which equates to a common term various outputs of milk having various concentrations of chemical components.The gross energy (or heat of combustion) value represents the most common characteristic to which all organic substances can be reduced.However, the direct measurement of the gross energy value is expensive of time and money and, therefore, is impractical to employ in many situations.In lieu of using gross energy as the basis of equating the milk output, Gaines (3) in 1928 proposed the use of 4% fat-corrected milk (4% FCM, to be abbreviated hereafter, FCM).The accuracy of Gaines' equation for estimat-